What Are the Risks of Vaccines?

Vaccines are very safe, but they are not 100% risk free.

They are certainly not as high risk as some anti-vaccine folks will have you believe though.

“Vaccine hesitation is associated with perceived risk. Since vaccine-preventable diseases are rare, an adverse event from a vaccine is perceived by the parent to be of greater risk. Risk perception is critical.”

AAP on Addressing Common Concerns of Vaccine-Hesitant Parents

And when you consider their great benefits, it is easy to see why the great majority of parents get their kids fully vaccinated and protected against all recommended vaccine-preventable diseases.

Risk Perception and Vaccine Hesitancy

Even though the risks and side effects of vaccines are very low, some people think that they are much higher. This is often amplified because of vaccine scare stories and the misinformation found on anti-vaccine websites.

“No intervention is absolutely risk free. Even the journey to a physician’s office with the intention to receive a vaccination carries the risk of getting injured in an accident. With regards to risks of vaccination per se, one has to distinguish between real and perceived or alleged risks.”

Heininger on A risk–benefit analysis of vaccination

Other problems with risk perception include that some people:

  • can be more likely to avoid risks that are associated with an action or having to do something vs. those that involve doing nothing or avoiding an action, even if inaction (skipping or delaying a vaccine) is actually riskier
  • often think about risks based on their own personal experiences (you remember someone’s vaccine injury story), rather than on scientific evidence

These biases in the way we think about risk can actually lead us to make risky choices and they help explain why some people are still so afraid of vaccines. Parents might think the risk of a possible side effect, some of which don’t even exist, is worse than the risk of getting a vaccine-preventable disease, getting someone else sick, or starting an outbreak. Parents also often underestimate the risk of their decision to not vaccinate their child.

“As much previous research claims, this study confirms that individuals characterized by greater trust of healthcare professionals and the possession of more vaccine-related knowledge perceive higher levels of benefits and lower levels of risks from vaccinations.”

Song on Understanding Public Perceptions of Benefits and Risks of Childhood Vaccinations in the United States

So what’s the answer? It is likely for folks to get better educated about vaccines, including getting a good understanding of both their benefits and risks.

What Are the Risks of Vaccines?

Again, vaccines are not 100% safe or risk free.

Most vaccines have some common, mild side effects, which might include (depending on the vaccine):

Vaccine Information Statements from the CDC highlight the risks of each vaccine.
Vaccine Information Statements from the CDC highlight the risks of each vaccine.
  • fever, typically low-grade
  • redness or swelling where the shot was given
  • soreness or tenderness where the shot was given
  • fussiness
  • headache
  • tiredness or poor appetite
  • vomiting
  • mild rash
  • diarrhea
  • swollen glands

How commonly do they occur?

It depends on the vaccine and side effect, but they range from about 1 in 50 to 1 in 3 people. These side effects are typically mild and only last a day or two. And they don’t cause lasting problems.

While not all possible side effects are mild, those that are more moderate or severe are much more uncommon. Febrile seizures, for example, only happen after about 1 out of 3,000 doses of MMR and some other vaccines. And while scary, febrile seizures, crying for 3 hours or more, or having a very swollen arm or leg, some other uncommon vaccine side effects, also don’t cause lasting problems.

Fortunately, the most severe side effects, including severe allergic reactions, are only thought to happen in less than 1 out of a million doses. And although these types of severe reactions can be life threatening, they are often treatable, just like severe allergic reactions to peanuts. For others, like encephalitis, although they are table injuries, it isn’t clear that they are even side effects of vaccines, since they occur so rarely.

All of these side effects can be reported to the Vaccine Adverse Event Reporting System (VAERS), either by your doctor or yourself.

“No medical product or intervention, from aspirin to heart surgery, can ever be guaranteed 100% safe. Even though we will never be able to ensure 100% safety, we know that the risks of vaccine-preventable diseases by far outweigh those of the vaccines administered to prevent them.”

World Health Organization

In addition to side effects, some other risks of getting vaccinated might include that your vaccine didn’t work, after all, although vaccines work very well, they are not 100% effective. You might also, very rarely, be given the wrong vaccine or the right vaccine at the wrong time.

Many other things, including so-called vaccine induced diseases, aren’t actually a risk of vaccines at all. Remember, autism, SIDS, multiple sclerosis, and shaken-baby syndrome, etc., are not a risk of vaccines.

What to Know About the Risks of Vaccines

Any small risks of getting vaccinated, including side effects that are often mild, are not a good reason to think about skipping or delaying a vaccine, especially when you thoughtfully consider all of their great benefits.

More About the Risks of Vaccines

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