November 2nd, 2009

Reports NPR:

With the swine flu virus more widespread than ever and concerns about availability of the vaccine circulating, we solicited your questions about the pandemic. NPR’s health editors, Joe Neel and Anne Gudenkauf, teamed up with Dr. Andrew Pekosz and Dr. William Schaffner to tackle your questions.

Pekosz is an expert on viruses and immunology and a professor at Johns Hopkins Bloomberg School of Public Health. Schaffner is an infectious disease expert and professor at Vanderbilt University.

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What is the efficacy of flu vaccines in general? I’m not clear, especially given the recent article published in The Atlantic? — Jennifer Meegan from Bozeman, Mont.

Influenza vaccines vary in their effectiveness, but overall they do their job quite well. Among young, healthy people, flu vaccines are 80 percent or more effective in preventing the strains of the disease contained in the vaccine.

Older people, and people who are in some way immunocompromised or have underlying illnesses such as heart disease or diabetes have a less effective immune response. For them, the vaccine may not prevent them from catching the flu, but it should keep the disease mild if they do catch it. So this group may still get a day or two of flu, but the vaccine helps to prevent complications like pneumonia, hospitalization and death.

But there is a key way the 2009 H1N1 vaccine is different from seasonal flu vaccines. For seasonal flu, experts make their best, educated guess about what flu strains will be dominant that year and make the vaccines to protect against those strains. So if they guessed the wrong strain, the vaccine doesn’t offer protection. Also, there’s a chance that multiple strains are circulating during flu season.

However, “the H1N1 vaccine is not only on target, but it’s a bull’s eye right in middle — this is a maximally effective influenza vaccine,” Schaffner says, because the H1N1 flu virus has remained incredibly genetically stable since last spring.

My younger son (then 13) got the swine flu last spring. But what about my older son (16)? He shares his room with his brother, so was exposed to the germs. Should he be considered immune? — Neal Rauch from the Washington, D.C., area

Unless your son has had a laboratory-confirmed case of 2009 H1N1 — not just a confirmed case of influenza, or unless you believe that your son’s flu-like symptoms were an infection with 2009 H1N1 — you should not assume that your son had swine flu or your other son was exposed to it. Getting vaccinated is the best way to ensure you are protected from influenza, so both your sons should get the vaccine, Pekosz says.

Exposure to the flu doesn’t make you immune, Schaffner adds. And, there’s no adverse affect in vaccinating someone who has already had swine flu.

Visit NPR for many more questions and answers.