Immunogenicity of a monovalent pandemic influenza A H1N1 vaccine in health-care workers of a university hospital in Japan

• Published in: Microbiology and immunology Vol. 54; no. 10; p. 618
• Main Authors: Igari, Hidetoshi, Segawa, Shunsuke, Watanabe, Akira, Suzuki, Akiko, Watanabe, Mariko, Sakurai, Takayuki, Kuroda, Fuminobu, Watanabe, Masaharu, Tatsumi, Koichiro, Nakayama, Mikio, Nakayama, Toshinori, Suzuki, Kazuo, Sato, Takeyuki
• Format: Journal Article
• Language: English
• Published: Australia 01.10.2010
• Subjects: Adult; Aged; Antibodies, Viral - blood; Female; Health Personnel; Hospitals, University; Humans; Influenza A Virus, H1N1 Subtype - immunology; Influenza Vaccines - adverse effects; Influenza Vaccines - immunology; Japan; Male; Middle Aged; Pandemics; Prospective Studies; Vaccination; Japan
• ISSN: 0385-5600
• DOI: 10.1111/j.1348-0421.2010.00254.x

A phase III observational study evaluating a single-dose of an inactivated, split-virus, unadjuvanted AH1pdm vaccine in HCW was conducted. A safe and effective vaccine was needed after the emergence of AH1pdm in April 2009. We analyzed the immunogenicity and safety of the vaccine. A total of 409 subjects were enrolled and given 15 μg hemagglutinin antigen by s.c. injection. Antibody titers were measured using hemagglutination-inhibition antibody assays before vaccination and 28 days after. The co-primary immunogenicity end-points were the proportion of subjects with antibody titers of 1:40 or more, the proportion of subjects with either seroconversion or a significant increase in antibody titer, and the factor increase in geometric mean titer. We collected 389 pair samples. Antibody titers of 1:40 or more were observed in 148 of 389 subjects (38.0%, 95% CI: 33.2-42.9). The immunogenicity was also confirmed in other end-points, but was not sufficient and was lower than in previous reports. A total of 96 of adverse events was reported: 51 local events and 57 systemic events. There were 12 subjects with both local and systemic events. Nearly all events were mild to moderate except in four subjects. A single 15-μg dose of AH1pdm vaccine did not induce sufficient immunogenicity in HCW, with mild-to-moderate vaccine-associated adverse events. We need to consider further improvement of the AH1pdm vaccine program in HCW for the prevention of nosocomial infection, as well as for the benefit of HCW.