National Institute of Allergy and Infectious Diseases



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Flu (Influenza)

H1N1 Vaccine Clinical Studies: Adults—Vaccine Size and Number of Doses Needed

Description

This trial started on August 7, 2009, and enrolled about 800 participants (400 healthy adults age 18-64 and 400 healthy adults aged 65 or older.) The purpose of the study is to look at whether one or two 15-microgram doses of H1N1 vaccine are needed to induce a potentially protective immune response in healthy adult volunteers. Researchers are also assessing whether one or two 30 microgram doses are needed. The doses were given 21 days apart, testing two manufacturers’ vaccines (Sanofi Pasteur and CSL Limited).

Locations

University of Maryland, Vanderbilt University, and Duke University used vaccine produced by Sanofi Pasteur. University of Iowa, Seattle Group Health Research Institute, and the University of Washington used vaccine produced by CSL.

Current Status

Early data (released September 11, 2009) indicate that 2009 H1N1 influenza vaccines are well tolerated and induce a strong immune response in most healthy adults when administered in a single 15-microgram dose.

Specifically, in blood samples obtained 8 to 10 days after vaccination:

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 aged 18 to 64 and in 56 percent of adults aged 65 and older.
Similarly, 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 aged 18 to 64 and in 60 percent of adults aged 65 and older.

On October 9, NIAID announced that data analyzed 21 days after the first dose of vaccine continues to show a strong immune response. For most adults, a single dose of 15 micrograms is needed.