Question 1. How Do Vaccines Work? Do They Work Against Viruses And Bacteria?
- Vaccines work to prime your immune system against future “attacks” by a particular disease. There are vaccines against both viral and bacterial pathogens, and disease-causing agents.
- When a pathogen enters your body, your immune system generates antibodies to try to fight it off. Depending on the strength of your immune response and how effectively the antibodies fight off the pathogen, you may or may not get sick.
- If you do fall ill, however, some of the antibodies that are created will remain in your body playing watchdog after you’re no longer sick. If you’re exposed to the same pathogen in the future, the antibodies will”recognize” it and fight it off.
- Vaccines work because of this function of the immune system. They’re made from a killed, weakened, or partial version of a pathogen. When you get a vaccine, whatever version of the pathogen it contains isn’t strong or plentiful enough to make you sick, but it’s enough for your immune system to generate antibodies against it. As a result, you gain future immunity against the disease without having gotten sick: if you’re exposed to the pathogen again, your immune system will recognize it and be able to fight it off.
- Some vaccines against bacteria are made with a form of the bacteria itself. In other cases, they may be made with a modified form of a toxin generated by the bacteria. Tetanus, for example, is not directly caused by the Clostridium tetani bacteria. Instead, its symptoms are primarily caused by tetanospasmin, a toxin generated by that bacterium. Some bacterial vaccines are therefore made with a weakened or inactivated version of the toxin that actually produces symptoms of illness. This weakened or inactivated toxin is called a toxoid. A tetanus immunization, for example, is made with tetanospasmin toxoid.
Question 2. Why Aren’t All Vaccines 100% Effective?
Vaccines are designed to generate an immune response that will protect the vaccinated individual during future exposures to the disease. Individual immune systems, however, are different enough that in some cases, a person’s immune system will not generate an adequate response. As a result, he or she will not be effectively protected after immunization.
That said, the effectiveness of most vaccines is high. After receiving the second dose of the MMR vaccine (measles, mumps and rubella) or the standalone measles vaccine, 99.7% of vaccinated individuals are immune to measles. The inactivated polio vaccine offers 99% effectiveness after three doses. The vermicelli (chickenpox) vaccine is between 85% and 90% effective in preventing all vermicelli infections, but 100% effective in preventing moderate and severe chicken pox.
Question 3. Why Are There So Many Vaccines?
Currently, the U.S. childhood vaccination schedule for children between birth and six years of age recommends immunizations for 14 different diseases. Some parents worry that this number seems high, particularly since some of the diseases being vaccinated against are now extremely rare in the United States.
Each disease for which vaccinations are recommended, however, can causes serious illness or death in unvaccinated populations, and might quickly begin to appear again if vaccination rates dropped. The United States has seen mumps outbreaks in recent years since vaccination rates have dropped, with severe complications and hospitalizations required for some patients. And before the introduction of the Hib (Haemophilus Influenzae Type b) vaccine, Hib meningitis affected more than 12,000 American children annually, killing 600 and leaving many others with seizures, deafness, and developmental disabilities. After introduction of the vaccine, the number of deaths from Hib dropped to fewer than 10 per year.
Each vaccine on the schedule continues to be recommended because of the risks posed by wild infection.
Question 4. Is Natural Immunity Better Than Vaccine-acquired Immunity?
In some cases, natural immunity is longer-lasting than the immunity gained from vaccination. The risks of natural infection, however, outweigh the risks of immunization for every recommended vaccine. For example, wild measles infection causes encephalitis (inflammation of the brain) for one in 1,000 infected individuals. Overall, measles infection kills two of every 1,000 infected individuals. In contrast, the combination MMR (measles, mumps and rubella) vaccine results in a severe allergic reaction only once in every million vaccinated individuals, while preventing measles infection. The benefits of vaccine-acquired immunity extraordinarily outweigh the serious risks of natural infection. (For more on this topic, see our Understanding Risks activity.)
Additionally, the Hib (Haemophilus Influenzae type b) and tetanus vaccines actually provide more effective immunity than natural infection.
Question 5. Why Do Some Vaccines Require Boosters?
It’s not completely understood why the length of acquired immunity varies with different vaccines. Some offer lifelong immunity with only one dose, while others require boosters in order to maintain immunity. Recent research has suggested that the persistence of immunity against a particular disease may depend on the speed with which that disease typically progresses through the body. If a disease progresses very rapidly, the immune system’s memory response (that is, the “watchdog antibodies” generated after a previous infection or vaccination) may not be able to respond quickly enough to prevent infection—unless they’ve been “reminded” about the disease fairly recently and are already watching for it. Boosters serve as a “reminder” to your immune system.
Research is continuing on the persistence of immunity generated by vaccines.
Question 6. My Child Was Invited To A Chickenpox Party. Would It Be Better For My Child To Get The Chickenpox This Way? Why Do We Vaccinate Against A Mild Disease Like Chickenpox?
The idea of “pox parties” is generally tied to the perception of chickenpox as a harmless illness. Before the vermicelli vaccine became available, however, chickenpox infections required 10,000 hospitalizations and caused more than 100 deaths each year in the United States. Exposing a child to wild chickenpox puts him at risk for a severe case of the disease.
Even uncomplicated cases of chickenpox cause children to miss a week or more of school, with a caregiver missing work to care for the sick child. Natural infection also means a risk of infecting others: while successful vaccination protects a child against chickenpox without this risk, children who are infected with chickenpox naturally are contagious. They can spread the disease to other people—not just other children, but also adults, who have a higher risk of complications from the disease.
Meanwhile, vaccination for chickenpox typically prevents future infection with the disease. In the rare cases where individuals do not develop adequate protection from vaccination to prevent future infection, chickenpox infection is typically mild, results in fewer symptoms, and ends more quickly than natural infection. (People with this mild form are contagious, however, and should take care not to expose others to the virus.)
Question 7. Can You Get A Disease From The Vaccine That’s Supposed To Prevent It? And Why Do Some Vaccines Have Live Pathogens But Others Have Killed Pathogens?
- Vaccines that are made with killed versions of pathogens—or with only a part of the pathogen—are not able to cause illness. When a person receives these vaccines, it is impossible for him or her to become ill with the disease.
- Live, attenuated (or weakened) vaccines are theoretically capable of causing illness: because they can still replicate (though not well), mutation is possible, which can result in a virulent form of the pathogen. However, they are designed with this in mind, and attenuated to minimize this possibility. Reversion to virulent form is a problem with some forms of the oral polio vaccine (OPV), which is why only the inactivated form (IPV) is now used in the United States.
- It is important to note that attenuated vaccines can cause serious problems for individuals with weakened immune systems, such as cancer patients. These individuals may receive a killed form of the vaccine if one is available. If not, their doctors may recommend against vaccination. In such cases, individuals rely on herd immunity for protection.
- As to why some vaccines contain live pathogens and others contain killed pathogens, the reasons vary by illness. However, generally speaking, live, attenuated vaccines generate longer-lasting immunity than killed vaccines. Thus, killed vaccines are more likely to require boosters to maintain immunity. Killed vaccines, however, also tend to be more stable for storage purposes, and can’t cause illness. The medical community must weigh these trade-offs in deciding which approach to use against a particular disease.
Question 8. Can Babies’ Immune Systems Handle So Many Vaccines?
Yes. Studies demonstrate that infants’ immune systems can handle receiving many vaccines at once—more than the number currently recommended. The immunization schedule is based on infants’ ability to generate immune responses, as well as when they are at risk of certain illnesses. For example, the immunity passed from mother to child at birth is only temporary, and typically does not include immunity against polio, hepatitis B, Haemophilus Influenzae type b, and other diseases that can be prevented by vaccination.
Question 9. Why Is There A New Flu Vaccine Every Year?
Unlike most vaccines, which contain the most common strains of a given pathogen (if more than one exists) and are rarely changed, the seasonal flu vaccine changes frequently, though one or more of the flu strains in the vaccine may be retained from one year to the next. This is because the strains of influenza viruses that circulate are constantly changing. Each year, researchers choose viruses for the vaccine based on which ones are likely to be circulating over the course of the coming flu season, thus providing protection against the most prevalent strains. So when you get a seasonal flu vaccine, you’re usually not getting another “dose” of the same flu vaccine you were given before. Instead, you’re usually getting protection against a whole new batch of flu viruses.
Question 10. What Is Herd Immunity? Is It Real? Does It Work?
Herd immunity, also known as community immunity, refers to the protection offered to everyone in a community by high vaccination rates. With enough people immunized against a given disease, it’s difficult for the disease to gain a foothold in the community. This offers some protection to those who are unable to receive vaccinations—including newborns and individuals with chronic illnesses—by reducing the likelihood of an outbreak that could expose them to the disease.
Question 11. Why Is Allergy To Eggs A Contraindication To Getting Some Vaccines?
Some vaccines, including the majority of vaccines against influenza, are cultured in chicken eggs. During the process of creating the vaccine, the majority of the egg protein is removed, but there is some concern that these vaccines might generate an allergic reaction in individuals with an egg allergy.
A recent report found that the majority of children with egg allergies who were given a flu shot had no adverse reactions; about 5% of children in the studied group developed relatively minor reactions such as hives, the majority of which resolved without treatment. Additional research is underway to study this issue further.
In most cases, only people with a severe (life-threatening) allergy to eggs are recommended against receiving egg-based vaccines.
Question 12. Do Vaccines Cause Autism?
No. Vaccines do not cause autism. This possibility was published after a 1998 paper by a British physician who claimed to have found evidence that the MMR (measles, mumps and rubella) vaccine was linked to autism. The potential link has been thoroughly explored; study after study has found no such link, and the original 1998 study has been formally withdrawn by The Lancet, which had originally published it. Studies were also done regarding the possibility of a link between the preservative thimerosal, which is used in some vaccines, and autism; again, no such link was found.
It’s likely that this misconception persists because of the coincidence of timing between early childhood vaccinations and the first appearance of symptoms of autism.
Question 13. People Say That Vaccines Are Linked To Long-term Health Problems Such As Multiple Sclerosis, Diabetes, And Autism. Is That True?
All vaccines have possible side effects. Most, however, are mild and temporary. Adverse effects from vaccines are monitored thoroughly via multiple reporting systems, and there is no evidence from these systems to support these claims.
Question 14. The Vaccine Information Sheet For My Child’s Recent Vaccination Listed Lots Of Potential Side Effects. Why Is Vaccination Recommended If It Can Cause All Of These Side Effects?
Every vaccine has potential side effects. Typically they are very mild: soreness at the injection site (for a vaccine delivered via a shot), headaches, and low-grade fevers are examples of common vaccine side effects. Serious side effects are possible, however, including severe allergic reactions. However, the occurrence of these side effects is extremely rare. (Your doctor can explain the risks for individual vaccines in detail; more information is also available from the Centers for Disease Control and Prevention.)
When considering possible side effects from vaccination, it’s important to do so in context. While some possible side effects are serious, they are extremely rare. It’s important to remember is that choosing not to vaccinate also has serious risks. Vaccines protect against potentially fatal infectious diseases; avoiding vaccination raises the risk of contracting those diseases and spreading them to others.
Question 15. Do We Do Enough Safety Testing With Vaccines?
Vaccines are tested repeatedly before being approved, and continue to be monitored for adverse reactions after their release. See our article on vaccine testing and safety for more information and details about this topic.
Question 16. Do Vaccines Have Aborted Fetal Tissue?
No. The rubella vaccine virus that is included in the MMR (measles, mumps and rubella) shot is cultured using human cell lines. The vaccine material is carefully separated from the cells in which is was grown before being used.
Some of these cell lines were generated from fetal tissue that was obtained in the 1960s from legal abortions. No new fetal issue is required to generate rubella vaccine.
Question 17. Isn’t It True That Better Hygiene And Nutrition Were Responsible For Decreases In Deaths And Disease Rates, Rather Than Vaccines?
Improved hygiene and nutrition, among other factors, can certainly lower the incidence of some diseases. Data documenting the number of cases of a disease before and after the introduction of a vaccine, however, demonstrate that vaccines are overwhelmingly responsible for the largest drops in disease rates. Measles cases, for example, numbered anywhere from 300,000 to 800,000 a year in the United States between 1950 and 1963, when a newly licensed measles vaccine went into widespread use. By 1965, U.S. measles cases were beginning a dramatic drop. In 1968 about 22,000 cases were reported (a drop of 97.25% from the height of 800,000 cases in just three years); by 1998, the number of cases averaged about 100 per year or less. A similar post-vaccination drop occurred with most diseases for which vaccines are available.
Perhaps the best evidence that vaccines, and not hygiene and nutrition, are responsible for the sharp drop in disease and death rates is chickenpox. If hygiene and nutrition alone were enough to prevent infectious diseases, chickenpox rates would have dropped long before the introduction of the vermicelli vaccine, which was not available until the mid-1990s. Instead, the number of chickenpox cases in the United States in the early 1990s, before the vaccine was introduced in 1995, was about four million a year. By 2004, the disease incidence had dropped by about 85%.
Question 18. Why Can’t We Eradicate Other Diseases, As We Did With Smallpox?
- In theory, nearly any infectious disease for which an effective vaccine exists should be eradicable. With sufficient vaccination levels and coordination between public health organizations, a disease can be prevented from gaining a foothold anywhere; eventually, without anyone to infect, it must die off. (A notable exception is tetanus, which is infectious but not contagious: it’s caused by a bacterium commonly found in animal feces, among other places. Thus, tetanus could not be eradicated without completely removing the Clostridium tetani bacterium from the planet.)
- Smallpox is unusual, however, in the set of characteristics that made it susceptible to eradication. Unlike many other infectious diseases, smallpox has no animal reservoir. That is, it can’t “hide” in an animal population and re-emerge to infect humans, while some diseases can do just that (yellow fever, for example, can infect some primates; if a mosquito then bites an infected primate, it can transmit the virus back to humans).
- Another obstacle to eradication for many infectious diseases is visibility. People with smallpox were highly visible: the smallpox rash was easily recognizable, so that new cases could be detected quickly. Vaccination efforts could be focused based on the location of the cases and potential exposure to other individuals. Polio, by contrast, causes no visible symptoms in about 90% of the people it infects. As a result, tracking the spread of the polio virus is extremely difficult, which makes it a difficult eradication target.
- Perhaps most importantly, smallpox patients generally did not reach their highest level of infectivity (that is, their ability to infect others) until after the appearance of the smallpox rash. As a result, quick action to quarantine infected individuals upon the eruption of the rash usually left enough time to vaccinate anyone who had already been exposed, and prevent additional exposures. Many infectious diseases do not allow for this kind of reaction time. Measles patients, for example, can become infectious up to four days before the appearance of the measles rash. As a result, they can pass the virus on to many, many other people before anyone even knows that they are infected.
- Many people still think eradication is possible for certain diseases. Efforts are ongoing to eradicate polio and Guinea worm disease (Dracunculiasis), with both having been eliminated in many regions, but remaining endemic in several countries. Meanwhile, the Carter Center International Task Force for Disease Eradication has declared additional diseases as potentially eradicable: lymphatic filariasis (Elephantiasis), mumps, pork tapeworm, and yaws.
Question 19. Is The Polio Vaccine Linked To Hiv?
In the 1990s, certain critics began to blame the testing of a live, weakened polio vaccine in Africa in the 1950s for the spread of acquired immune deficiency syndrome (AIDS). Those behind the accusation argued that chimpanzee cells were used to create the vaccine, and that those cells had been contaminated with a virus that sometimes affects chimps: simian immunodeficiency virus, or SIV. When the vaccine was given to children in Africa, they argued, SIV mutated to become human immunodeficiency virus, or HIV, which causes AIDS.
The accusations, however, were demonstrably false for a variety of reasons. Most notably, the weakened polio vaccine was not made with chimpanzee cells, but with monkey cells. The vaccine was later tested using a technique that can detect viral DNA (the PCR technique, or polymerase chain reaction); it did not contain SIV or HIV.
Researchers at the University of Birmingham in Alabama demonstrated in 2006 that while HIV was in fact a derivative of SIV, chimpanzees in Cameroon that had been infected with SIV in the 1930s were the most likely source of the AIDS epidemic—decades before the weakened polio vaccine was tested in Africa.
Question 20. Is The Polio Vaccine Linked With Cancer?
The polio vaccines developed by Jonas Salk and Albert Sabin in the mid-20th century were made with monkey cells. Years later, microbiologist Maurice Hilleman found a monkey virus in both vaccines—the 40th monkey virus to be discovered, which he called Simian Virus 40 (SV40). (Salk’s killed vaccine, which had been treated with formaldehyde, had very small amounts of the virus; Sabin’s live vaccine was heavily contaminated.) Worried about the potential effects the virus could have on humans, Hilleman injected it into hamsters, finding that nearly all of them developed massive cancerous tumors. But the initial panic this caused gave way in the face of future studies.
First, hamsters that ingested SV40 instead of being injected with it didn’t get cancer. Sabin’s live vaccine (which contained more SV40 than Salk’s) was given orally. Additional studies showed that children who were given Sabin’s vaccine did not develop antibodies to SV40; it simply passed through their digestive system, never causing infection.
That left only Salk’s vaccine, which contained very little SV40, but was given by injection. Studies performed eight years, fifteen years, and thirty years after SV40-contaminated vaccines had been given to children found that they had the same cancer incidence as unvaccinated groups. No credible evidence suggests that SV40 has ever caused cancer in humans.
Question 21. Will My Child Be Protected By Herd Immunity If I Don’t Get Them Vaccinated?
See our page on herd immunity for an explanation of what herd immunity is.
There are some problems with this idea:
- Herd immunity will not definitely protect anyone who is not vaccinated. There are low vaccination rates in some parts of the UK and in some communities. This means that if your child is not vaccinated, it is quite likely that many of the people they come into contact with will not be vaccinated either. So if one person gets an infectious disease, it can spread quickly through all the unvaccinated people in the group (this happened during the 2013 measles outbreak in Wales).
- For herd immunity to work properly, most people in the population need to be vaccinated. The exact rate depends on the disease; in the case of measles, 19 out of 20 people need to be vaccinated to protect the population. When measles vaccination levels drop below this level, outbreaks and epidemics become more common. So if you decide not to vaccinate because you think that herd immunity will protect you, you are making it less likely that you will be protected.
- Herd immunity does not protect against all diseases. The best example of this is tetanus, which is caught from bacteria in the environment, not from other people who have the disease. It doesn’t matter how many people around you are vaccinated against tetanus – it will not protect you as an individual.
Question 22. ‘if There’s An Outbreak Of A Disease Like Measles I Can Always Get My Child Vaccinated Then, Can’t I?’
Because of the way vaccines work, this can put a child at risk. For many diseases, one dose of vaccine does not give full protection. Some vaccines do work with a single dose, but it can take two or three weeks for the body to develop good levels of antibodies to protect against the disease.
So if a vaccine is given at the start of an outbreak it may not act quickly enough to protect your child. The other problem is that many diseases are infectious before any symptoms show, so your child could catch a disease before you even realise there is an outbreak.
Question 23. Does Breastfeeding My Baby Protects Them From Infectious Diseases?
Breast milk does contain some antibodies which are passed to the baby, especially in the first few days. However, this ‘passive immunity’ wears off after a few weeks, and after that breastfeeding offers very little protection from serious infectious diseases. It is therefore best to get your child vaccinated even if you are breastfeeding long-term.
Question 24. Will A Good Diet And Plenty Of Exercise Help To Prevent My Children From Getting Infectious Diseases?
To some extent, it will. Children with severe malnutrition are more at risk of disease, and a good diet is an important part of keeping healthy.
However, healthy children in wealthy countries are still at risk from conditions such as meningitis and septicemia (severe blood poisoning). There is also strong evidence that healthy, non-immunized children are more affected than adults during outbreaks of infectious disease because they have wider social networks and come into close contact with more people. There is no evidence that an organic diet offers any greater protection.
Question 25. Can I Use Homeopathic Remedies To Protect My Child?
There is no evidence that homeopathic medicine can protect against serious infectious diseases.
Even the Faculty of Homeopathy, a UK organisation which aims to ensure high standards in homeopathic practice and training, states that ‘When there is no medical contraindication…immunization should be carried out according to the current protocol using approved vaccines.’
Question 26. Will Catching An Infectious Disease Make My Child’s Immune System Stronger?
During any infection by bacteria or viruses, our immune system makes antibodies to fight that particular disease. For many diseases, an ‘immune memory’ is then created in special white blood cells called T lymphocytes. If we come into contact with the same disease, these white blood cells will ‘remember’ it and react quickly to fight it, so that we do not become ill. However, this process can only protect you against the specific disease that you have had. It does not make it easier for the body to respond to other kinds of infections.
The measles virus actually seriously damages and suppresses the whole immune system. Measles infection destroys the white blood cells that hold the ‘immune memory’, wiping out our immunity to diseases we have already had. This makes it much more likely that people who have had measles will catch other infections, even ones they have had before. Research published in 2015 found that it can take the body up to three years to recover from this damage. Before a measles vaccine was available, it is estimated that measles was the direct or indirect cause of over half of all childhood deaths from infectious disease.
Question 27. I Thought That People Only Died Of Infectious Diseases In The Past Because Medical Treatment Wasn’t Very Good?
This is not true. Today more people survive infection because of better medical care and medicines such as antibiotics, but infectious diseases are still dangerous.
People sometimes think that if their child gets a disease like measles or tetanus nowadays, a visit to the doctor or hospital will easily sort it out. In fact many infectious diseases lead to complications that still cannot be treated, even with the best medical care available (for example meningitis, encephalitis – inflammation of the brain – and even pneumonia). Even in countries with good intensive care facilities, 3 in 10 of those who get tetanus will die.
Question 28. Isn’t It True That Infectious Diseases Were Declining In Wealthy Countries Before Any Vaccinations Were Introduced?
This is true to some extent. In the early part of the 20th century better hygiene and sanitation, clean water and better food all contributed to better health. Smaller families and less crowded living conditions meant that diseases were not passed on so easily. Medicine and supportive care were both improving, so that people who caught a disease were less likely to die, and those who ended up with serious disabilities could be kept alive.
However, without vaccination it would have been impossible to reduce the levels of infectious diseases like measles to almost zero.
For example, before the Hib vaccine was introduced in 1992, there were thousands of cases of Hib disease every year in the UK. Now there are almost none. Living conditions have not really changed since 1992, so the decline in Hib disease can only be down to the vaccine. Improved living conditions have also made almost no impact on chickenpox. This disease is just as common now as it ever was, with an estimated 600,000 cases a year in the UK.
Question 29. What Sort Of Protection Do Vaccines Really Offer?
- No medicine in the world is 100% effective, but vaccines are more effective than many other medicines (up to 99.7% in the case of the measles vaccine). It is true that not all vaccines give lifelong protection, and that some individuals may be better protected than others, but there are several things to bear in mind:
- Catching a disease doesn’t always give you 100% immunity either. It is possible to catch tetanus, rubella, Hib disease, pertussis (whooping cough) and meningococcal disease more than once.
- If most of the population is vaccinated, this raises protection for everyone to almost 100%. See our page on herd immunity for more information.
- If someone who has been vaccinated in the past catches a disease, the symptoms are often milder than they would be for an unvaccinated person.
Question 30. Is It Safe For Babies And Children To Have Several Vaccines At Once?
Parents may worry that a child’s immune system will not be able to cope with several vaccines at once. In fact, even a tiny baby’s immune system can cope easily. Starting from birth, babies come into contact with millions of germs every day. It is estimated that the human body contains enough white blood cells to cope with thousands of vaccines at any one time. If a child was given 11 vaccines at once, it would only use about a thousandth of the immune system. It is not a good idea to delay vaccinations to ‘spread the load’, because it leaves the child unprotected against serious diseases for longer. See our page on Combination and Multiple Vaccinations.
Vaccines also challenge the immune system less than a disease does. This is because they use only part of the bacteria or virus that causes the disease, or a weakened form of the bacteria or virus. This is enough to make the body produce antibodies, but not enough to cause illness.
Question 31. My Baby Was Born Prematurely. Is It Safe For Him/her To Be Vaccinated?
Even premature babies can cope with vaccines. It is a good idea to vaccinate them because they have a higher risk of catching infectious diseases.
Question 32. How Do I Know That Vaccines Are Safe And Have Been Tested Properly?
All vaccines go through a long and thorough process of development and testing before they are licensed for use. It can take as much as 20 years for a vaccine to go from first concept to being licensed. Vaccines have to be tested on adults and children separately before they can be used for different age groups; this is because vaccines that work in adults may not work so well in children. No vaccines are tested on children before they have been fully tested on adults. See our page on Testing and Monitoring for more information.
Question 33. What About The Long-term Negative Effects Of Vaccination That We Don’t Yet Know About?
Nothing in life, including vaccination, can be completely risk-free, but so far all the evidence tells us that vaccinating is safer than not vaccinating.
It is rare for people to have serious reactions to vaccines, and so it is difficult to research these reactions because it takes a long time to gather examples to study. All serious reactions that get reported are investigated by the MHRA (Medicines and Healthcare products Regulatory Agency). See our pages on Vaccine side effects and adverse events and Testing and Monitoring for more information.
Question 34. Is There A Link Between Vaccination And Allergies?
Allergies and auto-immune diseases are on the increase, and it is understandable that people want to know what is causing this. Many researchers have looked at this issue, but they have found no evidence that vaccination is the cause, or that vaccination will trigger allergies. Allergy UK states that ‘All available information about immunization and allergy points to the fact that immunization in children who are at high risk of developing allergy is safe and not a factor in their future allergic conditions’ (see the Immunization Factsheet available to download on the Allergy UK website). See the abstract of the 2003 paper Addressing parents’ concerns: do vaccines cause allergic or autoimmune diseases.
There is no evidence at all that catching a serious disease like measles will help a child to fight off other kinds of infectious diseases when they are older.
Question 35. What About The Possible Link Between Mmr And Autism?
The original research which suggested a link has now been discredited. The National Autistic Society has issued a statement stating that the weight of evidence points to the fact that ‘there is no statistically significant link between the MMR vaccine and autism’. Watch this short film in which experts say why they believe there is no link between the MMR vaccine and autism, and see more on our MMR vaccine page (‘Is the vaccine safe?’ towards the bottom of the page).
Question 36. How Can I Find Out About The Side Effects Of Vaccines?
All side effects are listed in detail on the Summary of Product Characteristics sheet (SPCs) for each vaccine (see the list of SPECs on our Links page). SPCs are written for healthcare professionals, not the general public, and they can be quite hard to interpret. Side effects are listed in section 4.8 – Undesirable effects.
When looking at the rates of side effects, you need to remember that any unwanted symptoms experienced by participants during clinical trials of vaccines are recorded as potential side effects, even if they may not be the result of the vaccine. You also need to be aware that very rare side effects may be listed with no indication of how common they are (or described as ‘frequency unknown’), because they have not been reported often enough to get a clear idea of their frequency. See our page on vaccine side effects and adverse reactions.
It is a good idea to weigh up the risk of side effects against the risks involved in getting the disease itself (see our pages on Infectious Diseases for information about the risks of each disease).
Question 37. How Can I Find Out What’s Actually In The Vaccine?
The Patient Information Leaflets (PILs) and Summary of Product Characteristics sheets (SPCs) both give a full list of ingredients (usually called ‘excipients’). See the list of OILs and SPECs on our Links page. There is information about many of the ingredients found in vaccines on our Vaccine Ingredients page.
Vaccine ingredients can often look unfamiliar. However, it is important to remember that many of the substances used in vaccines are found naturally in the body. All vaccine ingredients are present in extremely small quantities, and there is no evidence that any of them cause any harm in these amounts.
Question 38. Is It True That Vaccines Can Cause The Diseases They Are Supposed To Protect Against?
This is true for some vaccines, but it happens very rarely. The live oral polio vaccine (not used in the UK since 2004) did cause polio in a handful of cases. In rare cases, attenuated (live but weakened) vaccines can cause mild forms of the diseases they protect against. For example, the MMR vaccine very occasionally causes measles, mumps or rubella, but the symptoms are almost always much milder than those caused by the diseases themselves.
This means that these kind of vaccines are only really a risk to children with weak immune systems (e.g. those with cancer), who have to rely on protection from herd immunity.
Question 39. Why Do The Vaccines Offered On The Nhs Seem To Change So Often?
Researchers are always looking for ways to improve the protection that vaccines give us. Sometimes they discover that it is better to give booster vaccines at different intervals. New or improved vaccines are being developed all the time, and once these are tested and approved they may be introduced into the UK schedule (for example, see information on the introduction of Preened and then Prevenar13 on our PCV page).
Researchers also try to identify the best possible protection that can be given by the smallest possible number of vaccines. Sometimes this leads to a vaccine being dropped from the schedule. For example, the dose of MenC vaccine given at 3 months of age was removed on 1st July 2016. See our blog post on this change.
Question 40. Diseases Like Polio And Diphtheria Don’t Occur In The Uk Any More. Why Does My Child Need To Be Vaccinated Against Them?
International travel means that any infectious disease is only a few hours’ flight away. Travelers to countries which still have diseases like polio and diphtheria can bring back these diseases to the UK, and this can put unvaccinated people at risk. For example, two unvaccinated children in Europe have died of diphtheria since the start of 2015. Once a disease is wiped out in every country in the world, vaccination is no longer necessary, but so far this has only happened in the case of smallpox.
Question 41. What Happens If I Decide Not To Get My Child Vaccinated And Then Change My Mind?
You can change your mind at any point. Even though it is better to get your child vaccinated at the ages recommended in the UK schedule, it is never too late to start vaccination. The majority of vaccines can be given at any point in childhood, so you can just go to your GP and ask them to give your child the vaccines they need.
Question 42. How Can I Get Hold Of Vaccines That Are Not In The Routine Uk Schedule?
Sometimes people want to obtain vaccines that are not offered routinely in the UK (for example, chickenpox vaccine for children, or whooping cough vaccine for adults visiting newborn babies in other countries). Any vaccines that are not part of the NHS provided service are only accessible through private provision. This may be through a private hospital, travel clinic or another GP practice (where you are not a registered patient).
Patients and parents who want to access vaccines privately are responsible for finding these services – unfortunately we don’t have a list of providers. Pricing may vary between different providers.
Question 43. Will The Injection Hurt My Child?
Yes, at the time, it might. Not all babies and children react in the same way, and some may not seem to feel any pain, but we all know that injections can hurt. Occasionally people may develop a fear of injections, so it is not a good idea to say things like ‘don’t worry, it won’t hurt’. However, there are ways to help reduce the pain that your child might feel.
- Breastfeed while the injection is taking place, or as soon as it is finished
- Sit your child upright – don’t lie them down
- Rub or stroke the skin near the injection site (before, during and after the injection)
- Deep breathing and blowing can help – get your child to blow bubbles or a pinwheel
- Let your child play with a toy so they are distracted during the injection, or have something ready for them to play with afterwards.
- See ‘Reducing the pain of childhood vaccination’ in the Canadian Medical Association Journal.
Question 44. Vaccination Just Isn’t A Very Nice Thing To Do A Child?
Vaccines can seem quite aggressive because they are usually injected rather than given by mouth.
The reason they are injected is simply that most vaccines are not absorbed well through the stomach. Vaccination is not designed to hurt anyone. Injection is just the best way of getting the vaccine into our bodies so that it can start to trigger the production of antibodies, which will then protect us against the disease.
Question 45. What Are The Real Risks Of Diseases Like Measles?
In many cases diseases like measles and mumps cause a few days of feeling unwell with no lasting complications. However, 1 in 15 children who have measles develop complications such as ear infections and fits. In a small but significant number of cases, many infectious diseases can lead to very serious, life-threatening conditions, and can kill. Measles is highly infectious and spreads very easily among people who have not been vaccinated.
Question 46. It’s Really Difficult To Weigh Up The Risks. Why Isn’t There More Information On The Chances Of Getting A Reaction To The Vaccine Compared To The Chances Of Getting The Disease?
This is not as straightforward as it sounds. It is fairly easy to find accurate information on some kinds of risk (for example, common side effects of vaccines). Some comparisons are also easy to understand (for example, 1 in 5000 children develop encephalitis as a complication of measles, but less than 1 in a million develop encephalitis as a complication of the MMR vaccine).
However, the chance of getting a disease is more difficult to work out, because it depends on how well-protected people are in your local community. If lots of people around you are unvaccinated, there is more chance of diseases spreading quickly than if you live in an area where most people are vaccinated, and this increases the risks. See our pages on Infectious Diseases for information about the risks of each disease.
Question 47. ‘it All Seems So Risky, I Just Won’t Do Anything’?
It can be difficult to weigh up the risks and decide what is best for your child. The problem is that the more scared you become about the possible risks on both sides, the more likely you are to do nothing. (You can see this on vaccination discussion forums where parents say they are so worried about the possible risks of both vaccinating and not vaccinating that they feel unable to make a decision at all.)
‘Doing nothing’ tends to make people feel less guilty if something goes wrong, because they can tell themselves that it’s just ‘bad luck’ or ‘an accident’ – they haven’t actually ‘done’ anything. It is important to bear in mind that ‘doing nothing’ is actually a decision which may have consequences, just as much as getting vaccinated. If you are aware of how you feel about the risks, and why, it may help you to come to a decision.
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