Seroprevalence of pandemic (H1N1) 2009 influenza and effectiveness of 2010/2011 influenza vaccine during 2010/2011 season in Beijing China

摘要

Please cite this paper as: Yang et al. (2011) Seroprevalence of pandemic (H1N1) 2009 influenza and effectiveness of 2010/2011 influenza vaccine during 2010/2011 season in Beijing, China. Influenza and Other Respiratory Viruses 6(6), 381–388. >Background  In the post‐pandemic period, pandemic (H1N1) 2009 virus was expected to circulate seasonally and was introduced into trivalent influenza vaccine during 2010/2011 season in the Northern Hemisphere. >Objectives  The aim of this study was to examine the evolution of herd immunity against pandemic (H1N1) 2009 virus in Beijing, China, during 2010/2011 season and effectiveness of the 2010/2011 trivalent vaccine. >Methods  Two serological surveys were conducted before and after 2010/2011 season in Beijing. A case–control study was used to investigate vaccine effectiveness against influenza‐like illness (ILI) and lower respiratory tract infection (LRI). >Results  A total of 4509 and 4543 subjects participated in the pre‐ and post‐season surveys, respectively. The standardized seroprevalence of pandemic (H1N1) 2009 influenza increased from 22·1% pre‐season to 24·3% post‐season (P < 0·001). Significant elevation in seroprevalence appeared in the ≥60 years age‐group (P < 0·001), but not in others. The 2010/2011 trivalent vaccine contributed to the higher post‐seasonal seroprevalence in unvaccinated individuals (P = 0·024), but not in those vaccinated with monovalent pandemic vaccine (P = 0·205), as well as in those without prior immunity versus those with immunity. The adjusted effectiveness of the 2010/2011 trivalent vaccine was 79% protection against ILI (95% CI, 61–89%) and 95% against LRI (95% CI: 59–99%). >Conclusions  A slight increase in herd immunity against pandemic (H1N1) 2009 influenza was observed in Beijing, China, during the 2010/2011 season. Prior vaccination and immunity had a suppressive impact on immune response toward this novel influenza virus, elicited by 2010/2011 trivalent vaccine. This trivalent vaccine conferred good protection against ILI and LRI.