By Rob Stein
Washington Post Staff Writer
Tuesday, November 3, 2009
Pregnant women need only one dose of vaccine to protect them from the swine flu, according to government data released Monday that confirm what officials have been recommending.
Federally funded studies also affirmed that children age 9 and younger will need two doses of vaccine to produce a strong enough response by their immune systems to protect them against the H1N1 virus, officials reported.
The findings came as an independent panel of experts organized by the Health and Human Services Department to monitor the safety of the vaccine met for the first time to review the data.
"No safety concerns have arisen," said Anthony S. Fauci of the National Institute of Allergy and Infectious Diseases, which has been leading the government's efforts to test the vaccine.
The government has begun an unprecedented campaign to inoculate millions of Americans against the swine flu virus, which is circulating widely in nearly all states. The program, however, has gotten off to a slower start than officials had hoped, with only about 30 million doses available, causing widespread frustration and anxiety as long lines have formed at clinics nationwide.
In the new results, an analysis of blood samples from 50 pregnant women in their second or third trimesters taken 21 days after they received a 15-microgram dose of vaccine found that 92 percent experienced a sufficient response to assume they would be protected. Although 96 percent of those who received a 30-microgram dose experienced a similarly strong response, officials concluded that the 15-microgram dose being used as a standard was sufficient.
"This should be reassuring news for those women who have already received the vaccine, and it is vital information for those women who have not been vaccinated," Fauci told reporters during a briefing.
Additional data from blood tests on 583 children, however, found that only 25 percent of those ages 6 months to 35 months and only 55 percent of those ages 3 to 9 years had a strong enough immune response to protect them 21 days after getting only one shot. But 100 percent of the young children and 94 percent of those ages 3 to 9 experienced a strong enough response eight to 10 days after a booster.
Although the World Health Organization said Friday that an expert panel it assembled to review data concluded that one dose may be sufficient, Fauci said the new findings reinforce the U.S. recommendations.
Previous results showed that most other adults also need only one shot.
The National Vaccine Advisory Committee's H1N1 Vaccine Safety Working Group, meanwhile, met for the first in what will be biweekly meetings to monitor the results of data being collected to detect any problems with the vaccine.
Summaries of information from more than 13,000 people who received the immunization in government-sponsored clinical trials concluded that "the rate and nature of local and systemic reactions following each dose appear to be acceptable and similar to other influenza vaccines. . . . To date, no serious adverse events have suggested any safety signals with H1N1 vaccines."
Although one death has been reported among people who received the immunization, that person died from the flu, not the vaccine, said Bruce Gellin, who heads the National Vaccine Program Office.
Although the vaccine was produced in record time, federal health officials have issued repeated assurances that there is no reason to doubt its safety, because it was manufactured by the same companies that have been making the seasonal flu vaccine for years, using the same process and the same facilities.