A single dose of vaccine against the pandemic H1N1 influenza virus provides a strong immune response in healthy pregnant women, but continuing studies confirm that two doses are required in children under 9, said Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, this morning at a news conference. Neither finding was a surprise, but they validate the guidelines of current immunization programs.
Meanwhile, 30 million doses of the swine flu vaccine are available as of this morning, an increase of 3.9 million since Friday, said Dr. Anne Schuchat, director of the Centers for Disease Control and Prevention's National Center for Immunization and Respiratory Disease, at the same conference. Some states have had to reschedule their vaccination programs because of temporary shortages, she added, but the situation "should be getting better every day."
The National Institute of Allergy and Infectious Diseases had enrolled 120 healthy pregnant volunteers in its vaccine trial by the middle of October, and the results today were on the first 50. In 25 women who received a single dose of vaccine containing 15 micrograms of antigen--the standard dose--23 showed a strong immune response. Among 25 who received double that dosage, 24 showed a strong response, Fauci said. "This is reassuring news to women who have already received the vaccine and important news to those who haven't," he said.
The agency had earlier reported results in children eight to 10 days after a single dose of vaccine, and results from 21 days corroborated the findings. Among children ages 6 to 35 months, 25% showed a strong response after 21 days. Among those ages 3 to 9 years, 55% showed a similar response. But eight to 10 days after both groups were given a second dose of the vaccine, 100% of the young children showed a strong response and 94% of the older ones. The results were not surprising because children in this age group typically require two doses of the seasonal flu vaccine the first time they are immunized because they retain no residual immunity from earlier infections or vaccinations.
Fauci emphasized that the only adverse events reported in any of the clinical trials have been redness and swelling of the arm, typical of all vaccinations.
Dr. Bruce Gellin, director of the Department of Health and Human Services' National Vaccine Program Office, said that there has been one death reported following vaccinations nationwide. Investigation showed that that person died of severe H1N1 disease that they contracted either before vaccination or before immunity had time to build up. As part of its routine planning, the office has assembled a group of non-government scientists to monitor vaccine safety in addition to all of the other programs already in place. That group met for the first time in Washington today.
-- Thomas H. Maugh II