The FDA has approved four vaccines to protect the population against the 2009 pandemic H1N1 influenza virus. About 45 million doses should be available at 90,000 sites in October. The government has ordered 195 million doses. CSL Ltd., MedImmune LLC, Sanofi-Pasteur, and Novartis Vaccines/Diagnostics Ltd. are using the same processes to make the H1N1 vaccines. Based on preliminary data, the 2009 H1N1 vaccines induce a robust immune response in most healthy adults eight to 10 days after a single dose. Clinical studies are under way to determine the optimal dose for children.
As with seasonal influenza vaccines, some of the H1N1 vaccines contain thimerosal, a mercury-containing preservative. People with severe or life-threatening allergies to chicken eggs, or to any other substance in the vaccine, should not be vaccinated.
In ongoing studies, the vaccines have been well tolerated thus far. For the injected vaccine, side effects may include soreness at the injection site, mild fever, body aches, and fatigue for a few days. For the nasal spray, adverse effects may include a runny nose or nasal congestion in people of all ages, sore throats in adults, and fever in children two to six years of age.
Vaccines against three seasonal virus strains are already available, but they do not protect against the 2009 H1N1 virus.
Sources: FDA, September 15, 2009;
Associated Press, September 16, 2009