About the Swine Flu Vaccine

Andrew Pekosz, an associate professor of molecular microbiology and immunology at Johns Hopkins University's Bloomberg School of Public Health in Baltimore, answers some questions about the H1N1 vaccine.

What is the difference between the nasal spray and the injectable vaccine for H1N1, or swine flu?

Just as there are two forms of seasonal influenza vaccine available to the general population, vaccine makers have produced two vaccines to prevent H1N1 infection. The nasal spray vaccine is a live virus that has been weakened so it doesn't cause disease in healthy people. The injectable vaccine contains an inactivated, or "dead," virus. The nasal spray vaccine can be used only in certain people: You must be between ages 2 and 49 and have no history of major health problems. The vaccine is not recommended for pregnant women. Remember to discuss these issues with your health-care provider.

I heard that vaccines are made with chicken eggs. Are the vaccines safe for people with egg allergies?

No. The virus in both the nasal spray and the injectable form is grown in eggs. So if you have an allergy to eggs or egg products, you should avoid the H1N1 vaccine.

My kids both got H1N1 at summer camp. Should I have them vaccinated?

If their H1N1 infections were confirmed to be 2009 H1N1 and not just "influenza" or "influenza A virus," then they most likely developed immunity to the virus and are unlikely to be infected again this fall or winter. Based on seasonal influenza data, there is no evidence suggesting that getting the vaccine after getting an infection leads to any increased adverse side effects. CDC says that people who think they have been infected should still get vaccinated against H1N1 to ensure they are protected.

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