How Are Vaccines Tested Before They Can Be Given to Kids?

Paul A. Offit, MD, explains how vaccines are tested before they can be given to kids or adults. He also discusses how vaccines are tested and monitored after approval.


How are vaccines tested before they can be given to kids?

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. And I think parents want to make sure that before a vaccine is licensed and recommended by groups like the Centers for Disease Control and Prevention or the American Academy of Pediatrics, that it’s been tested. I mean, has it been tested in enough people to make sure that it’s safe and that it’s effective?

Usually the way that that works — and these efforts are usually 20- to 25-year efforts — is that vaccines are tested in progressively larger number of initially adults, and then older children, and then younger children. First to make sure that they’re safe. That they don’t have any common side effect. Also to make sure that they induce an effective immune response. And then as you do larger and larger trials, ultimately progressing to what’s called the final definitive, Phase III trial, which usually can involve 50, 60, 70,000 children in the case of childhood vaccines. That’s when you’re looking to see whether or not … not only that it’s safe, which is to say that it doesn’t even cause relatively rare side effects, but also that it protects against disease. And some diseases are uncommon enough that you need to do large studies to figure that out.

But I think most importantly parents should know that even when a vaccine is licensed, and when it’s recommended, it’s always still being tested for safety, through groups like the Vaccine Safety Datalink, which is this large group of nine different health maintenance organizations. It involves a large percentage, actually, of the American population. So you can see when a vaccine starts to roll out. You can look at those children who got it, look at those children who didn’t get the vaccine to see whether there’s any difference in terms of safety issues.

So vaccines are always being tested for safety because they have to be. Frankly, we’re giving them to healthy children, so they need to be held to, frankly, the highest standard of safety.

Thank you.

Related Centers and Programs: Vaccine Education Center

Last Reviewed on Aug 11, 2015