FDA Approves H1N1 Vaccines

The FDA has approved four vaccines against the novel influenza A (H1N1) virus, and initial lots are expected to be distributed nationally within the next four weeks, according to a Sept. 15 news release from the agency.

The approved vaccines are manufactured by CSL Ltd., MedImmune LLC, Novartis Vaccines & Diagnostics Ltd. and sanofi pasteur Inc. following the same processes used to produce seasonal influenza vaccines.

The FDA said preliminary data from clinical trials indicate the vaccines induce a robust immune response in most healthy adults eight to 10 days after a single dose.

"Today's approval is good news for our nation's response to the 2009 H1N1 influenza virus," said FDA commissioner Margaret Hamburg, M.D., in the news release. "This vaccine will help protect individuals from serious illness and death from influenza."

The NIH's National Institute of Allergy and Infectious Diseases, or NIAID, conducted clinical trials of the vaccines produced by CSL and sanofi pasteur. In a Sept. 11 news release, NIAID director Anthony Fauci, M.D., said that among healthy adults who received a single, 15-microgram dose of the sanofi pasteur vaccine, a robust immune response was measured in 96 percent of adults ages 18-64 years and in 56 percent of adults ages 65 years and older.

Among healthy adults who received a single, 15-microgram dose of the CSL Limited vaccine, a robust immune response was measured in 80 percent of adults ages 18-64 years and in 60 percent of adults ages 65 years and older, Fauci said.

He added that the discrepancy between the sanofi pasteur and CSL vaccines may be due to technical differences in the preliminary measurement of the amounts of antigen in the doses used in the clinical trial lots, the relatively limited number of samples studied to date, and the fact that data was drawn soon after immunization.

"NIAID will continue to provide timely updates on these trials, as well as those in children and in pregnant women, which began later," he said.

A clinical trial of CSL's vaccine reported on Sept 10 in the New England Journal of Medicine found results similar to NIAID's findings with the sanofi pasteur vaccine. A single dose of unadjuvanted vaccine containing 15 micrograms of antigen was immunogenic in 96.7 percent of healthy adults within 21 days after vaccination. The study reported that no deaths or serious adverse events were reported.

The FDA said the vaccines have been well tolerated during clinical trials, and potential side effects of the H1N1 vaccines are expected to be similar to those experienced with seasonal influenza vaccines.

The most common side effect with injected H1N1 vaccine is soreness at the injection site; other side effects may include mild fever, body aches and fatigue for a few days after vaccination, said the FDA. The most common side effects from the nasal spray version of the H1N1 vaccine are runny nose or nasal congestion for all ages, sore throats in adults and fever in children 2-6 years of age.

Jesse Goodman, M.D., the FDA's acting chief scientist, said in the agency's release that H1N1 vaccines are subject to the same rigorous manufacturing oversight, product quality testing and lot release procedures that apply to seasonal influenza vaccines.