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

Abstract

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.

Differences in Antibody Responses of Individuals with Natural Infection and Those Vaccinated against Pandemic H1N1 2009 Influenza

“…Poor immunogenicity has also been reported in studies involving young healthcare workers and in the elderly (8,20). In Hong Kong, the pandemic influenza vaccine was given as a single dose, and this may explain the relatively low seroprotection rate in the population in the present study.…”

Persistence and avidity maturation of antibodies to A(H1N1)pdm09 in healthcare workers following repeated annual vaccinations

“…Lower seroprotective titers have been reported for HCWs in Hong Kong (54%) and Japan (38%) after one dose of un-adjuvanted A(H1N1)pdm09 vaccine [37,38]. These inferior responses may be attributed to lack of adjuvant in the vaccines administered in these studies.…”

Electronic cigarettes efficacy and safety at 12 months: cohort study

“…CO levels suggestive of tobacco smoking (>7 ppm) [18] were found in only three subjects (two tobacco smokers and one e-smoker), who admitted the error and were accordingly re-classified.…”