Tag: side effects

How Often Do Severe Events Occur After Vaccines?

Most of us understand that vaccine reactions are usually mild. While severe events can occur after vaccines, they are very rare.

“That measles infections can cause neurologic side effects on rare occasions is known, but the complication rate for vaccinations is low. After infectious measles encephalitis, risk of an autistic regression has occurred in 1/1000 to 1/10,000 cases. If the trend toward delaying vaccination continues because parents remain misinformed about the MMR, the number of children with neurologic complications of measles or rubella will increase. ”

Chez et al on Immunizations, Immunology, and Autism

Unfortunately, being worried about severe reactions sometimes scares parents away from vaccinating and protecting their kids.

How Often Do Severe Events Occur After Vaccines?

Hopefully, realizing just how rare these severe reactions are will help more parents understand that all of the benefits of vaccines (very big) truly do outweigh the risks (very small).

How often do severe events occur after MMR vaccines?
How often do severe events occur after MMR vaccines?

So how often do these events occur?

Are there any statistics?

Using the MMR vaccine information statement as an example, we see that it lists the following severe events:

  • deafness – which is so rare to be associated with MMR that it is hard to tell whether they are caused by the vaccine
  • long-term seizures, coma, or lowered consciousness – which is so rare to be associated with MMR that it is hard to tell whether they are caused by the vaccine
  • brain damage – which is so rare to be associated with MMR that it is hard to tell whether they are caused by the vaccine
  • severe allergic reaction – which occurs in less than 1 out of a million doses
  • serious injury or death – which is so rare to be associated with MMR that it is hard to tell whether they are caused by the vaccine

Wait.

Why can’t we tell if these problems are caused by the vaccine?

In some cases, the association is based on a few case reports.

“With respect to the recent claims of deaths caused by MMR vaccine, drawing broad cause and effect conclusions between vaccination and deaths based on spontaneous reports to VAERS, some of which might be anecdotal or second hand, is not a scientifically valid practice. In fact, a review of the VAERS data reveals that many of the death reports for MMR vaccine involved children with serious preexisting medical conditions or were likely unrelated to vaccination (e.g., accidents). These complete VAERS reports and any accompanying medical records, autopsy reports and death certificates have been reviewed in depth by FDA and CDC physicians and no concerning patterns have emerged that would suggest a causal relationship with the MMR vaccine and death.”

Miller et al on Deaths following vaccination: What does the evidence show?

Mostly though, these type of severe events just occur so rarely after getting vaccinated.

“As for vaccines causing death, again so few deaths can plausibly be attributed to vaccines that it is hard to assess the risk statistically.”

WHO on Six common misconceptions about immunization

At a rate of less than 1 in a million doses, it gets hard to know if something was really caused by the vaccine or if it was just a coincidence, as you don’t have a lot of cases to compare with each other.

Still, it should be reassuring that even if they were caused by the vaccine, these serious events are extremely rare.

Vaccines are safe, with few risks.

More on How Often Severe Events Occur After Vaccines

Side Effects and Adverse Events Following Immunizations

Vaccines are safe, but they do have some side effects, mostly mild, and they rarely cause some serious and severe adverse reactions.

Vaccine adverse events can be reported to VAERS online or using a downloadable form.
Vaccine adverse events can be reported to VAERS online or using a downloadable form.

To help keep our vaccines safe, it is important that all “clinically important adverse events that occur after vaccination of adults and children” be reported to VAERS, not just the ones that are known to be side effects.

Wait.

Isn’t an adverse event the same as a side effect?

Adverse Events Following Immunizations

To better understand that, let’s first look at how we define an adverse event following immunization (AEFI):

“An Adverse event following immunization (AEFI) is any untoward medical occurrence which follows immunization and which does not necessarily have a causal relationship with the usage of the vaccine. The adverse event may be any unfavourable or unintended sign, abnormal laboratory finding, symptom or disease.”

Classification of AEFIs

So it should be clear that not all adverse events are actually caused by vaccines.

Many are coincidental events that simply occur after a vaccine is given.

What’s the Difference Between Side Effects and Adverse Events Following Immunizations?

Others are true vaccine reactions though, including fever, pain, fainting, and allergic reactions, etc.

“A side effect is any health problem shown by studies to be caused by a vaccine. Like any medication, vaccines can cause side effects. Usually vaccine side effects are minor (for example, a sore arm where a shot was given or a low-grade fever after a vaccine) and go away on their own within a few days.”

Understanding Side Effects and Adverse Events

These are the reactions that we call side effects or adverse reactions of the vaccine.

Still, just because a sign or symptom can be a side effect of a vaccine doesn’t mean that it always will be.

“A vaccine reaction is an individual’s response to the inherent properties of the vaccine, even when the vaccine has been prepared, handled and administered correctly.”

Vaccine reactions – WHO Vaccine Safety Basics

Here are some other definitions:

  • adverse event – Medical occurrence temporally associated with the use of a medicinal product, but not necessarily causally related.
  • adverse reaction/side effect – A response to a drug which is noxious and unintended, and which occurs at doses normally used in man for the prophylaxis, diagnosis, or therapy of disease, or for the modifications of physiological function.
  • unexpected adverse reaction – Not consistent with applicable product information or characteristics of drug.
  • severe adverse event or reaction – are rarely life-threatening and usually do not result in long-term problems
  • serious adverse event or reaction – Any untoward medical occurrence that at any dose is life-threatening, results in death, requires inpatient hospitalization or prolongation of existing hospitalization, or results in persistent of significant disability or incapacity

Does understanding those definitions make it easier to see why you should be skeptical when folks try to scare you with VAERS reports and data from package inserts?

“Reports of all possible associations between vaccines and adverse events (possible side effects) are filed in VAERS. Therefore, VAERS collects data on any adverse event following vaccination, be it coincidental or truly caused by a vaccine. The report of an adverse event to VAERS is not documentation that a vaccine caused the event.”

Guide to Interpreting VAERS Data

They both can include reports about adverse events, not just side effects. So they both include events that can very well be coincidental, and not caused by a vaccine.

So when doing your research about vaccines, focus on real side effects, or things that are known to be caused by vaccines. You will find that most vaccine side effects are mild and that more serious or severe side effects are very rare.

More on Side Effects and Adverse Events

Are There Any Long-Term Studies On Vaccine Safety?

Vaccines are evaluated for safety in studies when they get approved.

Is that enough?

“I would like to see us do more long-term safety research studies on these large groups of children, so then we can determine that they are safe in the long-term.”

Bob Sears

Apparently not for everyone…

Are There Any Long-Term Studies On Vaccine Safety?

Of course, vaccines continue to be evaluated for safety after they approved, using passive and active vaccine safety systems and long-term post-marketing safety studies.

“We learn about a vaccine’s safety during clinical trials before it is licensed, and monitor it continually as millions of doses are administered after it is licensed. We also know there is not a plausible biologic reason to believe vaccines would cause any serious long-term effects. Based on more than 50 years of experience with vaccines, we can say that the likelihood that a vaccine will cause unanticipated long-term problems is extremely low.”

Parents’ Guide to Childhood Immunizations

These long term studies on vaccine safety have looked at:

Have you heard about these studies before?

When they talk about SV40, do anti-vaccine folks mention this long-term study?
When they talk about SV40, do anti-vaccine folks mention this long-term study?

Probably not.

Anti-vaccine folks either aren’t aware of, or just don’t want you to know about these types of long-term studies.

It’s easier to scare you away from vaccinating and protecting your kids if they make you believe that vaccines aren’t tested together, aren’t tested with placebos, aren’t tested vs unvaccinated kids, and aren’t tested for long periods of time.

They are!

More on Long-Term Studies On Vaccine Safety

Anaphylaxis After Vaccines

Anaphylaxis after vaccines is a well known side effect, but just how common is it?

Anaphylaxis After Vaccines

Since it is listed as a possible reaction to nearly all vaccines and it can be life-threatening, anaphylaxis must be fairly common, right?

“Vaccine providers should be familiar with identifying immediate-type allergic reactions, including anaphylaxis, and be competent in treating these events at the time of vaccine administration. Providers should also have a plan in place to contact emergency medical services immediately in the event of a severe acute vaccine reaction.”

Preventing and Managing Adverse Reactions

After all, pediatricians even get warned to have a plan in place and to be prepared to treat children just in case they develop anaphylaxis after getting their vaccines.

Your pediatrician will likely have an EpiPen in the office in case your child has an anaplylactic reaction after his vaccines.
Epi Is Readily Available to Treat Most Kids with Anaphylaxis After Vaccines

Still, most probably have never had to.

“Any medication can cause a severe allergic reaction. Such reactions to a vaccine are estimated at about 1 in a million doses, and would happen within a few minutes to a few hours after the vaccination.”

Possible Side-effects from Vaccines

And that’s because anaphylaxis after vaccines is very rare.

Anaphylaxis After Vaccines is Rarely Fatal

And suprisingly, it is even more rare for these cases to be fatal!

“All 30 patients with anaphylaxis survived (9 reports specified anaphylaxis, and we classified another 21 as probable cases, based on compatible clinical features, including respiratory and skin symptoms within 4 hours after vaccination). In half of 22 detailed reports, symptoms developed within 15 minutes after vaccination.”

Wise et al on Postlicensure Safety Surveillance for Varicella Vaccine

But that study just looked at the chicken pox vaccine and used VAERS, so we have to be concerned about under-reporting, right? Well, not necessarily. Under-reporting likely isn’t a big problem for serious reactions.

Anyway, that’s not the only study…

“We identified 33 confirmed vaccine-triggered anaphylaxis cases that occurred after 25,173,965 vaccine doses. The rate of anaphylaxis was 1.31 (95% CI, 0.90-1.84) per million vaccine doses.”

McNeill et al on Risk of anaphylaxis after vaccination in children and adults

The McNeill study used the Vaccine Safety Datalink, which unlike VAERS, is not a passive reporting system. So there is no concern about underreporting.

And like the Wise study, there were no deaths among these vaccine-triggered anaphylaxis cases.

“Fatalities from vaccine-induced anaphylaxis are exceedingly rare.”

Adverse reactions to vaccines practice parameter 2012 update

Similarly, a study in the UK found rare reports of anaphylaxis after vaccines in children and all those children made a full recovery.

Parents should understand that while anaphylaxis is a known side effect to getting a vaccine, it is extremely rare, and can usually be treated. This once again reinforces that vaccines are safe!

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