One dose of swine flu vaccine may be enough for most adults

The news is good from the early swine (H1N1) flu vaccine trials. The first spate of preliminary results were published yesterday in the New England Journal of Medicine, and today by the Department of Health and Human Services, and most of the findings were positive. It had been suspected that most people would require two doses of vaccine, but the studies found a robust immune response to a single dose. More trials are underway for pregnant women, adults with immunodeficiency, and children. Authorities still expect that children will require two-doses, because their bodies have less experience developing immunity.

The safety profile of the swine-flu shot is also promising. The trials have produced no deaths or serious adverse events to date. The mild to moderate reactions that did occur included discomfort or pain at the injection site, which was reported in 46 percent of subjects in one study, and systemic symptoms such as headache, malaise, and muscle aches, reported in 45 percent.

Trials can't pick up extremely rare reactions, such as Guillian-Barré syndrome (GBS), a neurological disorder that can lead to paralysis and, in rare cases, death. A vaccine developed 30 years ago against a strain of the swine flu was linked to an increased—but still very rare—risk of GBS. Experts don't expect the same problem this time, but enhanced adverse event reporting systems are being put in place to monitor such events.

Who needs it? Swine flu doesn't appear to spread easily to people over 65, possibly because many have immunity from exposure to a similar strain decades ago. The Centers for Disease Control and Prevention has developed a list of people who should get vaccinated first. They are:

• Pregnant women
• People who live with or care for infants under 6 months
• Health care and emergency medical workers
• Children and adults between 6 months and 24 years old
• People aged 25 through 64 years old with underlying health conditions or compromised immune systems

Other patients can ask their doctor for the vaccine, and doctors can give it to them. But our consultants say that you should wait until supplies have reached high-risk people. People who have already had a confirmed case should ask their doctor if they need the vaccine, since the previous exposure may offer some protection.

The new expectation that adults will need just one shot is welcome news. Just a quarter of the planned 195 million doses the swine flu vaccine are expected to arrive in October. That can be spread across a wider swath of the populations if adults can skip a second dose. And they'll have immunity more quickly, in 8 to 10 days according to the HHS trial.

Seasonal flu vaccine available now

While the swine flu vaccine is expected to dominate the flu season, the seasonal flu is still expected to circulate. In a typical year it kills 36,000 people, and hospitalizes 200,000. It's best to get your shot early so you have immunity whenever it rolls around.

We recommend it for:

• Anyone who wants to avoid getting the flu
• All adults 50 and older
• All children 6 months to 18 years
• Pregnant women
• Anyone with asthma, emphysema, or chronic bronchitis, or heart, lung, kidney, or sickle-cell disease
• People with impaired immunity and their household members
• People who live with or care for infants under 6 months old
• Health care and emergency medical workers