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Swine Flu Vaccine: When?

Swine Flu Vaccine Timeline: Key Decisions, Key Milestones

Making Sure the Vaccine Is Safe

The most important question about a pandemic flu vaccine is whether it will be safe. Unfortunately, like nearly everything about flu bugs, safety can't be guaranteed 100%.

What's reassuring is that there's been no safety issue with previous H1N1 flu vaccines. We take them every year. There are rare adverse events, but the benefit of vaccination far outweighs this small risk.

Safety tests will be performed on the new vaccines. But there won't be a lot of time to see what happens in the long term. If the vaccines seem relatively safe -- that is, if they don't seem harmful in the first weeks after they're administered -- they'll be rolled out on a massive scale. That means relatively rare side effects will be seen only after millions of people are vaccinated.

The last time the nation faced something called swine flu was in 1976. That's when a flu of swine origin struck an army base, triggering fears of a pandemic. A vaccine was rushed into production. Manufacturers demanded that the government indemnify them against possible injury claims, making the public wary before vaccination even began.

It's still not clear why a rare but serious neurological disorder called Guillain-Barre syndrome hit those vaccinated in 1976 at a higher-than-expected rate. But after some 44 million Americans received the vaccine, safety fears scuttled the vaccination program -- and gave "swine flu vaccine" a bad name that still lingers in the American psyche.

How the public perceives the safety of the vaccine will depend on how severe the flu pandemic turns out to be, flu expert Andrew Pavia, MD, said at a June meeting at the Institute of Medicine.

"If this were a 1918-like pandemic, we could tolerate a fair degree of risk," Pavia said. "But for this virus, our sensitivity to risk is going to be much more difficult to calibrate."

September

One Dose or Two?

By mid-September, results from clinical studies will show the best dose for pandemic swine flu vaccine, how many doses are needed for which populations, and whether the vaccine appears safe in different populations.

If the decision was made in August to start packaging vaccine doses, vaccine will become available around Sept. 15. Early results from clinical trials will guide the decision whether to start vaccinating people. But that decision will have to be made before officials have all the information they'd like to have.

A huge question is whether it will take two doses of vaccine to immunize against pandemic flu. It's possible that because this is a new flu, everyone will be like a small child. Children who've never had a flu shot need two flu vaccinations, weeks apart, to be immunized.

But it might take only one shot. Or maybe some people could get by with one shot -- perhaps those who have had repeated seasonal flu shots, those who have been infected with seasonal H1N1 flu, or those born before 1957 when a different H1N1 flu circulated.

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