Seroepidemiology of novel influenza A (H1N1) infection among HIV-infected patients in the era of highly active antiretroviral therapy.

BACKGROUND: The seroprevalence and seroincidence of novel influenza A infection among HIV-infected patients, who were believed to have more severe outcomes than healthy individuals, are rarely investigated in the era of highly active antiretroviral therapy (HAART). Our aim was to determine the seroprevalence and seroincidence of novel influenza A infection among HIV-infected patients in Taiwan.
METHODS: Between September and November 2009, before the implementation of a nationwide vaccination for novel influenza A in Taiwan, 931 HIV-infected patients and 566 persons seeking voluntary counseling and testing (VCT) for HIV infection at our university hospital were enrolled in this study. Antibody responses to novel influenza A were determined using a hemagglutination-inhibition (HI) assay.
RESULTS: HIV-infected patients had a significantly lower seroprevalence of novel influenza A infection than VCT clients (14.7% vs. 33.9%, p < 0.001). The seroincidence of novel influenza A infection among HIV-infected patients was 9.4% (95% confidence interval [CI]: 7.6-11.4). On the multivariate analysis, heterosexual (odds ratio [OR]: 1.89; 95% CI: 1.105-3.227) and baseline HI titer (OR: 1.02; 95% CI: 1.001-1.038) were significantly associated with seroconversion to novel influenza A virus.
CONCLUSION: HIV-infected patients demonstrated a lower seroprevalence of novel influenza A infection than HIV-uninfected patients in Taiwan in the HAART era. Among HIV-infected patients, seroconversion to novel influenza A virus, which was infrequent during the 2009 influenza epidemic, was associated with heterosexual behavior and baseline HI titer.