The first results from tests of swine flu vaccines in humans are in, and it looks like a single shot will be enough to protect people from the H1N1 virus.
A single shot should keep H1N1 at bay.
A single shot should keep H1N1 at bay. CDC
Officials had worried two doses of vaccine might be required. But, as an editorial accompanying the online publication of two studies in the New England Journal of Medicine says, the data support beginning with a one-shot plan.
The results mean scarce supplies of vaccine can go farther and immunization can be done more quickly than if a two-shot regimen were required. For more, listen to this report from NPR's Joanne Silberner.
Young children may need a second dose because their immune systems don't always respond strongly to vaccines like the one against swine flu, but it's not clear that's the case. In any event, flu vaccine shouldn't be held back with that in mind, the editorial says.
Both NEJM papers show one dose of vaccine prodded the bodies of adult volunteers to produce a substantial antibody reaction against the new virus. One of the studies looked at a vaccine that had an added ingredient called an adjuvant to boost immune response. That kind of vaccine is unlikely to be approved for use in the US this flu season.
Pain and tenderness at the point of injection were the most common side effects. The study groups were too small to detect extremely rare side effects that might show up when tens of millions of people are immunized, however.