How Effective Is Spray Swine Flu Vaccine For Kids?

By Joanne Silberner

Here we go with some more swine flu questions and answers. In an email to the blog, Renee Boulis, of Wyomissing, Pa., asks about the nasal spray form of vaccine against the new H1N1 virus.

Three-year-old Abby Hilterbran receives a nasal vaccination in Piqua, Ohio, on Monday. (Mike Ullery/AP)

How effective is the protection for children under 8, ask Boulis, who often babysits two young grandchildren? Is it possible for them to transmit the virus to others while they are waiting for the second spritz?

Let's take your first question first.

The short answer on effectiveness in children is that a single dose is not as effective as people would like. Two doses get the job done.

The National Institute of Allergy and Infectious Diseases just released the results of a study on children under the age of 10. This study used the injectable vaccine, but scientists say the results hold for the nasal spray as well.

After the first shot, researchers looked for signs in the kids' blood that they'd be able to fight off infection. Only 25 percent of children between the ages of 6 and 35 months had a strong enough response three weeks after the first dose, and only 55 percent of those 3 to 9 years old were protected.

After the second dose, though, all the 6 to 35 month olds and 94 percent of the 3 to 9 year olds were protected. That's why the U.S. government is sticking to its recommendation that kids get two doses. The World Health Organization is opting for just one.

Now for the second question. Are they infectious while they're waiting for the second spritz?

It sounds like your grandchildren got the nasal spray vaccine, which contains a weakened but still living flu virus. According to the Centers for Disease Control and Prevention:

In clinical studies, transmission of vaccine viruses to close contacts has occurred only rarely. The current estimated risk of getting infected with vaccine virus after close contact with a person vaccinated with the nasal-spray flu vaccine is low (0.6%-2.4%). Because the viruses are weakened, infection is unlikely to result in influenza illness symptoms.

So there's a slight chance your grandchildren could infect you, and a close-to-zero chance that you'd develop symptoms.

In any event, you can get at least some protection if you and your grandchildren follow good hygiene practices: wash hands often, and cough or sneeze into a tissue or your elbow.

If you've got a swine flu question, email us at shots@npr.org. Please let us know where you're from when you write.