Diagnosing Vaccine Injuries

Vaccine Basics

Vaccine books to help you do your vaccine research.
Reading some of these books will help you to get educated about vaccines, make the right choice for your children, and get them protected against vaccine-preventable diseases. Photo by Vincent Iannelli, MD

Vaccines are often described as one of the greatest public health achievements of the 20th century. There is no doubt for most people that vaccines have prevented millions of deaths from vaccine-preventable diseases.

That great benefit also leaves no doubt for most people that getting vaccinated and fully protected far outweighs the very small risk of any vaccine injuries.

Vaccine Injuries vs Vaccine Side Effects

Vaccines can certainly have side effects.

Fever, pain at the injection site, and redness and swelling where the shot was given are all common, mild problems that can be associated with almost any vaccine.

Some vaccines might also commonly cause fussiness, tiredness or poor appetite, and vomiting within 1 to 3 days of getting the vaccine. Others can cause a rash, headache, or muscle and joint pain for a few days.

Even syncope or fainting can commonly occur within 15 minutes of teens getting a vaccine.

Other vaccine side effects can include persistent crying, nodules at the injection site, limb swelling, and febrile seizures, etc.

These are well-known vaccine side effects that are minor and temporary, though. They are not the much more rare type of serious vaccine side effects that might be classified as a vaccine injury.

Types of Vaccine Injuries

Vaccines can very rarely cause these types of vaccine injuries (conditions list on the National Vaccine Injury Compensation Program's Vaccine Injury Table):

  • life-threatening allergic reactions
  • brachial neuritis (shoulder pain and then weakness) following a tetanus containing vaccine
  • encephalopathy/encephalitis following a measles, mumps, or rubella, or pertussis containing vaccine
  • chronic arthritis following a rubella containing vaccine
  • thrombocytopenic purpura (TTP) following a measles containing vaccine
  • vaccine-strain measles viral infection in an immunodeficient recipient following a measles containing vaccine
  • intussusception following a rotavirus vaccine

Still, while vaccines are associated with some serious adverse events, the research is clear that vaccines don't cause autism, SIDS, and shaken baby syndrome, type 1 diabetes, multiple sclerosis, and inflammatory bowel disease, etc.

And simply being on the vaccine injury table doesn't necessarily mean that the vaccine was the cause of the 'injury.' In a Canadian study of encephalopathy related to pertussis vaccine, out of over 6.5 million doses of vaccines given between 1993 and 2002, they found only 7 cases of encephalopathy beginning within 7 days of receiving a pertussis containing vaccine, but all 7 had a more likely cause than the vaccine. The final diagnosis for these children's encephalopathy included herpes simplex encephalitis, influenza A encephalopathy (3 patients), parainfluenza encephalopathy, a probable gastrointestinal infection, and adrenal insufficiency in a child with previous episodes of hypoglycemia.

And studies show that vaccines on the current childhood immunization schedule don't cause encephalitis.

Diagnosing Vaccine Injuries

How do you know if your child had a vaccine injury?

Does the reaction fit into the vaccine injury type AND "time period for first symptom or manifestation of onset or of significant aggravation after vaccine administration" as described in the NVICP vaccine injury tables?

The time period, also known as a risk interval, is when "individuals are considered at risk for the development of a certain adverse event following immunization (AEFI) potentially caused by the vaccine."

For example, did your child develop an anaphylactic reaction within fours of getting the DTaP vaccine? While a reaction 14 hours after the vaccine would be much less likely to be caused by the vaccine, if it occurred within 4 hours, that could certainly be a vaccine injury.

How about a child who developed thrombocytopenic purpura 90 days after getting his MMR vaccine? That is unlikely to be a vaccine injury, as the MMR vaccine typically causes TTP within 7 to 30 days.

If you think that your child has had a vaccine injury, be sure to talk to your pediatrician. You and your pediatrician should also report any vaccine reaction to Vaccine Adverse Event Reporting System (VAERS).

Among the things that your pediatrician will consider when evaluating an adverse event after a vaccine will be the answers to some key questions, including:

  • Is there evidence for other causes for the reaction? While a vaccine could cause an anaphylactic reaction shortly after vaccination, so could the fact that your child just ate a peanut butter and jelly sandwich.
  • Is there a known causal association between the reaction and the vaccine?
  • Is there strong evidence against a causal association between the reaction and the vaccine?
  • Is there a laboratory test that implicates the vaccine as a cause of the reaction?
  • If the reaction is an infection, did it have a vaccine or wild type origin?

Your pediatrician might also consider other qualifying factors, whether other patients were affected, and will make sure that the original diagnosis is correct.

Being able to answer all of these questions often puts pediatricians in the unique position of correctly evaluating potential vaccine injuries. There is even a standardized algorithm that can help your pediatrician collect and interpret all of the data they will get when evaluating a possible vaccine injury.

Another algorithm can help evaluate and manage suspected allergic reactions, including immediate or type 1 hypersensitivity reactions and delayed type 3 hypersensitivity reactions. If the reaction is consistent with an allergic reaction and additional doses of the vaccine are still needed, possible next steps in this algorithm include serologic testing for immunity and skin testing with the vaccine or vaccine components.

For extra help, your pediatrician can also consult an allergist or immunologist before revaccination. Experts at the Clinical Immunization Safety Assessment (CISA) are also available for consults about suspect vaccine injuries.

Over-diagnosing Vaccine Injuries

In addition to vaccine side effects and vaccine injuries, it is much more common for children and adults to develop health problems and symptoms after getting a vaccine that have nothing to do with the vaccine. These events would have happened even if they had not been vaccinated.

Parents may think that these events were caused by vaccine injuries because they might:

For example, studies have repeatedly shown that "vaccination does not increase the overall risk of sudden infant death (SIDS)," and that "the risk of SIDS in vaccinated cases and controls is neither increased nor reduced during the early post-vaccination period." So a VAERS report of SIDS on the night that an infant received his 4 month vaccines, while tragic, would likely not end up being classified as a true vaccine injury.

Neither would all of the reports of autism in VAERS.

Subsequence and Consequence

Dr. Samuel Johnson once said that "It is incident to physicians, I am afraid, beyond all other men, to mistake subsequence for consequence."

How does this apply to diagnosing vaccine injuries?

Too often we forget that just because one event is subsequent (happens after) another, it does not mean that it was a consequence (was caused by) the first event. It is another way of saying that correlation does not imply causation.

This is also highlighted by missed vaccine stories, events that would surely be blamed on a vaccine injury, except for the fact that a vaccine was not actually given for one reason or another.

Many pediatricians have these types of missed vaccine stories, such as:

  • an infant who begins vomiting on the way home from a well child appointment and is diagnosed with intussusception (9-month-old visit and didn't get any vaccines)
  • a 4-year-old who developed encephalitis just one week after his well check up (no vaccines - DTP had been deferred to his 5-year-old visit)
  • a 2-month-old who died of SIDS on the night of his scheduled well child visit (no vaccines as they had forgotten to go to the appointment)
  • a 4-month-old who had a seizure at his well child visit (no vaccines were given yet as they were still being drawn up)

Or they have kids who begin to have symptoms or are diagnosed with a condition right around the time of a check up, when they would routinely get one or more vaccines but hadn't yet. From diabetes to transverse myelitis, some parents would have blamed their child's vaccines if they had actually been vaccinated at the time and subsequently gotten diagnosed.

My own son started getting migraines when he was 12 years old and about to start 7th grade. Should I blame his headaches on his middle school booster shots? While it would be convenient, it is more likely that genetics are to blame. I started getting migraines at about the same age, and he began getting them just before he got his booster shots, not after.

Mis-using Package Inserts

Another reason that vaccine injuries can be over-diagnosed is that instead of using established diagnostic guidelines, parents and some pediatricians might instead misuse a vaccine's package insert.

How can that happen?

Consider the package insert for Prevnar, which states that the "most commonly reported serious adverse events were in the 'Infections and infestations' system organ class including" bronchiolitis, gastroenteritis, pneumonia.

Does that mean that Prevnar can cause pneumonia, a vaccine that prevents Streptococcus pneumoniae infections, which can include pneumonia?

Of course not. Prevnar is not a live vaccine, so you wouldn't expect it to be able to cause any of those types of infections. You would expect it to be listed as an adverse reaction if you understand how vaccine package inserts are created.

Instead of recording only those side effects that are definitely caused by the vaccine, manufacturers record "those adverse events for which there is SOME BASIS TO BELIEVE there is a causal relationship between the drug and the occurrence of the adverse event." And in the case of clinical trial's data, as with the Prevnar 'Infections and infestations' adverse events, they may record all of things that happened to the people in the trial for up to 30 days or longer after they got their dose of vaccine.

It is easy to see why you must interpret this adverse event data instead of just taking it at face value when you look at a vaccine with a placebo-controlled study. In the package insert for Rotarix, a vaccine that protects against rotavirus, you can see that some percentage of all vaccinated infants developed:

  • fussiness/irritability
  • cough/runny nose
  • fever
  • loss of appetite
  • vomiting
  • diarrhea

However, an almost equal, and sometimes higher number of infants in the placebo group developed the same exact symptoms.

Looking at RotaTeq, another vaccine that was involved in placebo-controlled clinical trials, you can see that the "most frequently reported serious adverse events for RotaTeq compared to placebo" included:

  • bronchiolitis (0.6% RotaTeq vs. 0.7% Placebo)
  • gastroenteritis (0.2% RotaTeq vs. 0.3% Placebo)
  • pneumonia (0.2% RotaTeq vs. 0.2% Placebo)
  • fever (0.1% RotaTeq vs. 0.1% Placebo)
  • urinary tract infection (0.1% RotaTeq vs. 0.1% Placebo)

The rate of SIDS was also the same in the RotaTeq vaccine and placebo groups.

Vaccines are Safe

Study after study have proven that vaccines are safe.

In the past 25 years, the Institute of Medicine has reviewed research and studies concerning possible vaccine side effects 11 times. The last IOM review, in 2011, "concluded that few health problems are caused by or clearly associated with vaccines."

Vaccines do not cause autism, SIDS, diabetes, or most other things that some people consider to be vaccine injuries. And even though the original DTP vaccine was associated with more side effects than the newer DTaP vaccine that replaced it, several studies have shown that DTP did not cause encephalopathy. Many children that were suspected of having encephalopathy instead had Dravet syndrome.

Not only did vaccines not cause encephalitis in any of the children in a Canadian study, 3 of the 7 children's encephalitis was actually caused by influenza, a life-threatening, vaccine-preventable disease!

That fact reinforces the point that in addition to being safe, vaccines are important and necessary to keep our children safe and healthy.

Get Educated. Get Vaccinated. Stop the Outbreaks.


CDC. General Recommendations on Immunization: Recommendations of the Advisory Committee on Immunization Practices (ACIP). MMWR. January 28, 2011 / 60(RR02);1-60.

Halsey, Neal A, et al. Algorithm to assess causality after individual adverse events following immunizations. Vaccine. Volume 30, Issue 39, 24 August 2012, Pages 5791–5798

Institute of Medicine. Adverse Effects of Vaccines: Evidence and Causality. Washington, DC: The National Academy Press; 2011

Kuhnert, Ronny, et al. Reanalyses of case-control studies examining the temporal association between sudden infant death syndrome and vaccination. Vaccine. Volume 30, Issue 13. 16 March 2012. pp 2349-2356.

Maglione et al. Safety of Vaccines Used for Routine Immunization of US Children: A Systematic Review. PEDIATRICS Volume 134, Number 2, August 2014.

Moore DL. Lack of evidence of encephalopathy related to pertussis vaccine: active surveillance by IMPACT, Canada, 1993-2002. Pediatr Infect Dis J. 2004 Jun;23(6):568-71.

Pahud, Barbara A.Lack of association between childhood immunizations and encephalitis in California, 1998–2008. Vaccine, Volume 30, Issue 2, 5 January 2012, Pages 247-253

Rowhani-Rahbar, Ali. Biologically plausible and evidence-based risk intervals in immunization safety research. Vaccine. Volume 31, Issue 1, 17 December 2012, Pages 271–277

Schattner, Ami. Consequence or coincidence?: The occurrence, pathogenesis and significance of autoimmune manifestations after viral vaccines. Vaccine, Volume 23, Issue 30, 10 June 2005, Pages 3876-3886

Wood, Robert A, et al. An Algorithm for Treatment of Patients With Hypersensitivity Reactions After Vaccines. Pediatrics 2008;122;e771.

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