Serologic survey of pandemic influenza A (H1N1 2009) in Beijing, China.

ABSTRACT

OBJECTIVE: To examine the frequency and distribution of antibodies against pandemic influenza A (H1N1 2009) [H1N1] in populations in Beijing and elucidate influencing factors. METHODS: In January 2010, a randomized serologic survey of pandemic influenza A (H1N1 2009) was carried out. Six districts that were randomly selected with a total of 4601 participants involved in the survey have their antibody level tested by hemagglutination inhibition assay. RESULTS: Among the 4601 participants, the overall seropositive rate for pandemic influenza A (H1N1 2009) antibodies was 31.7%. The seropositivity prevalence in participants who received the pandemic H1N1 vaccination was 60.9%. Only 53.1% of the pandemic influenza A (H1N1 2009) seropositive individuals who had not received the vaccination experienced respiratory tract infection symptoms. Multivariate logistic regression revealed that factors such as age, occupation, dwelling type, whether the participant's family included students in school, and the vaccination history with pandemic influenza A (H1N1 2009) were associated with antibody titers (p<0.05). CONCLUSIONS: Our data indicated that almost 30.0% of the residents had appropriate antibody titers against pandemic influenza A (H1N1 2009) in Beijing, and these titers may provide an immune barrier.