Are Vaccines Safe?

Paul A. Offit, MD, discusses the definition of “safe” in the context of vaccination, and explains the benefits versus risks of vaccines and vaccine-preventable diseases.


Are vaccines safe?

Paul Offit, MD: Hi, my name’s Paul Offit. I’m talking to you today from the Vaccine Education Center here at The Children’s Hospital of Philadelphia. I think probably one of the most common question we get asked is, “Are vaccines safe?” I think another way to frame that would be that, “Do the benefits of vaccines clearly and definitively outweigh the risk?”

And, I think the answer to that questions, assuming one doesn’t have a medical counter indication to a vaccine, is yes. I think the benefits clearly and definitively do outweigh the risk. But that doesn’t mean that there are no risks. Because there are risks to vaccines. Certainly, when you get a vaccine there could be pain, or redness, or tenderness at the site of injection. Sometimes vaccines can cause fever, including high fever for young children. Fever can often induce something called a febrile seizure. And although febrile seizure don’t cause any permanent harm, they can be very hard for any parent to watch.

So vaccines do cause those side effects. Rarely, vaccines can cause more severe side effects. So for example, the oral polio vaccine that was given in this country from the early 1960s up until around the year 2000, could very rarely, in about 1 per 2.4 million doses, cause polio itself. That’s why we went away from that vaccine by the year 2000, and now use only the so-called inactivated polio vaccine, which doesn’t cause that problem.

There was an issue in 1976 associated with swine flu vaccine that was given in this country, where that vaccine was found to be a very rare cause of something called Guillain-Barré Syndrome, which is an ascending paralysis that can also be quite severe. It was found to be a consequence of that vaccine in roughly 1 per 100,000 recipients.

Measles-containing vaccine, like measles virus, can cause something called thrombocytopenia, which just means a lowering of the platelet count. That can cause these sort of little broken blood vessels, so-called petechia to be seen on the skin. It’s transient, it’s very rare, occurring in about 1 per 30,000 people. But again, it is a possible consequence of that vaccine.

And certainly vaccines can contain components like gelatin, which is used as a stabilizer, or egg proteins, which can be allergenic, causing occasionally severe hypersensitivity or allergic responses.

So, I think the most important thing for parents to remember is that while vaccines aren’t risk free, a choice not to get a vaccine is not a risk-free choice, it’s a choice to take a different and far more serious risk. Because these diseases can cause a tremendous amount of suffering, and hospitalization, and death. So, I think parents should be reassured that vaccines are safe and that their benefits clearly outweigh other risks.

Thank you.

Related Centers and Programs: Vaccine Education Center

Last Reviewed on Aug 11, 2015