Vaccine Myths and FAQs: How do we know vaccines are safe?

In the Hippocratic oath, doctors commit to “first do no harm.” The most important thing I want families to know about me as a doctor is that I would not recommend anything if I had any reasonable concern that it could be harmful. All my colleagues in pediatrics feel the same way. So we’ve built a system to ensure that vaccines are safe and effective for kids to get. But it’s not uncommon for parents and the general public to misunderstand this system and the science it produces. So this post is to clarify some pieces of misinformation I’ve heard from parents.

Misinformation: Vaccines Are Untested

Fact: There is a higher level of scrutiny for the testing and regulation of vaccines than there is for any medication or nutritional or herbal supplement. The process of licensing a vaccine is depicted in the following infographic. First a vaccine is tested for safety and efficacy in animals. If it passes, it graduates to trials in small numbers of human volunteers which assess safety. If the data show it is safe, it graduates to trials with larger number to assess whether it is effective in preventing disease. These later trials involve up to tens of thousands of participants. When a vaccine has good data, it is presented to independent scientists at the FDA for approval as well as inspections of each lot of vaccine and manufacturing site. After the FDA approves the vaccine itself, then another independent committee of scientists and doctors called the Advisory Committee on Immunization Practices (ACIP) at the CDC review the data and decide whether to place it on the recommended immunization schedule. Furthermore, separate committee at the American Academy of Pediatrics and American Academy of Family Physicians weigh in as well as to whether they also recommend the shot after their own review of the data. Finally, it’s up to an individual physician whether they recommend the shot. As physicians we continue to review data published in medical journals regarding vaccine safety and efficacy. How this data is collected on an ongoing basis is explained next.

Misinformation: Vaccines Are Not Regulated. There are reports showing that vaccines cause many side effects.

Fact: When a vaccine is put into use, the VAERS system (Vaccine Adverse Event Reporting System) is an information gathering system that doctors, nurses, parents, patients -literally anyone- can use to report a potential vaccine reaction. Since it’s just an information gathering tool, though, VAERS cannot demonstrate that these are true side effects of the vaccine. If we took all VAERS reports in this database at face value, we would conclude that vaccines have literally turned kids into Spider-Man or the Hulk, because there are actual reports of this happening. But it is important to get as much information as we can get through VAERS. And it’s important to evaluate that information and be open to what the evidence is telling us.

The next step is for independent academic researchers (who are not part of vaccine manufacturing corporations) to use the data collected through VAERS to compare groups of children who got the vaccine with groups of children who didn’t. To do this, researchers use a mega database called the Vaccine Safety DataLink. If a shot causes a side effect, it should show up more often in the vaccinated group than the unvaccinated group. There is no system like this set up for any other medical intervention, and goes to show how careful the medical community we are about vaccines. On-going studies are constantly being done.

These kinds of studies have demonstrated no higher rates of autism in children who have received vaccines compared to children who haven’t. These findings have been replicated many times. Similar studies have demonstrated similar performance on neurocognitive testing between school aged kids who had been vaccinated as infants compared to those who hadn’ t been vaccinated as infants.

These kinds of studies have also occasionally led to doctors pulling the plug on certain vaccines, such as with Rotashield in 1998 when they found that there was 1-2 more cases of intussusception than expected for every 10,000 vaccinated children. This was subsequently replaced with two safer options, Rotateq, and Rotarix, which on-going surveillance has demonstrated don’t cause the same problem.

To read more about the processes in place to keep vaccinations safe, read this little primer on vaccine safety monitoring.

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