Abstract:
Background: Influenza vaccination is recommended during pregnancy. Maternal HIV and malaria infection may affect immune response to vaccination.
Methods: Immune responses to influenza vaccination and vertical antibody transfer were assessed in three groups of expectant mothers in western Kenya vaccinated before 31 weeks gestation: 1) HIV-positive; 2) malaria-positive; and 3) HIV-negative/malaria-negative. All participants received trivalent inactivated influenza vaccine. Maternal influenza antibody titers before vaccination (day 0), after vaccination (range 14-24 days), and at delivery were measured using hemagglutination inhibition assays (HAI). Infant HAI antibody titers were measured in cord blood and serum collected at 16 and 24 weeks of age. Seroconversion against each virus subtype was defined as four-fold rise in HAI titer with post-vaccination titer ≥1:40, and antibody seropositivity as HAI titers ≥40.
Results: During June 2018–January 2020, 355 pregnant women were enrolled and vaccinated (89 HIV-positive, 77 malaria-positive, and 189 HIV-negative/malaria-negative). Seroconversion ranged from 44%-63% against influenza A(H1N1)pdm09, 18-22% against B/Yamagata, 38-40% against B/Victoria, and 13%-28% against A(H3N2) vaccine strains. Transplacental antibody transfer was similar across all groups except for antibodies against influenza A(H3N2) among HIV-infected women with viral load ≥200 copies/mL, and women who had placental malaria.
Conclusion: This study documented immunogenicity of inactivated influenza vaccines among HIV-infected and malaria-infected pregnant women and vertical antibody transfer from mothers to infants. Data support importance of HIV treatment to achieve virologic control and improving malaria management for better vaccine efficacy, and increasing access to influenza vaccination among pregnant women.