A Prospective Immunogenicity Study of a Quadrivalent Inactivated Influenza Vaccine Among Persons With HIV With Different Levels of CD4 Cell Count

Introduction: Data regarding the immunogenicity of a quadrivalent inactivated influenza vaccine (IIV4) among persons with HIV with different levels of CD4 cell count are limited. Here, we report the immunogenicity of IIV4 in persons with HIV with different CD4 cell count levels by determining seroprotection (SP) and seroconversion rate after vaccination. Method: Persons with HIV were prospectively recruited to receive IIV4 (season 2021) between November 2021 and January 2022. Hemagglutination inhibition titers were assessed before and at 28 days after vaccination and classified as SP or seroconversion with comparison of characteristic between CD4 cell count >350 cells/mm 3 group and CD4 cell count ≤350 cells/mm 3 . Result: A total of 70 persons with HIV received the IIV4. The mean (SD) age was 48 (9) years, and 64% were men. Most of them (74%) were maintained on a nonnucleoside reverse transcriptase inhibitor–based regimen with an undetectable HIV viral load (100%). There was a significantly greater proportion of persons with HIV who achieved SP against A/Hong Kong/2571/2019-like virus (H3N2) variant in those with CD4 cell count >350 cells/mm 3 compared with those with CD4 cell count ≤350 cells/mm 3 (98.3% vs. 72.3%), relative risk 1.35 (95% confidence interval: 1.13 to 1.61, P = 0.011). Furthermore, the participants with CD4 cell count >350 cells/mm 3 were significantly more likely to achieve SP against B/Phuket/287/2013 strain (98.3% vs. 72.3%, relative risk 1.35; 95% confidence interval: 1.13 to 1.61, P = 0.011). Conclusion: Persons with HIV with greater CD4 cell count could achieve a higher chance of SP against B/Phuket/287/2013 and A/Hong Kong/2571/2019-like virus (H3N2) strains after IIV4 vaccination. Therefore, new strategies should be investigated and offered to those with low CD4 cell counts.