In a study conducted among nearly 500 influenza vaccine-naive mother-infant pairs in Malawi, researchers found that maternal HIV infection was associated with lower antibody responses to influenza A viruses in both mothers and their infants, suggesting that influenza vaccines “may have variable efficacy in sub-Saharan Africa” where there is a high burden of HIV, researchers said.
In the study, neither HIV nor malaria infection impaired transplacental transfer of influenza antibodies — one of the ways maternal vaccination protects infants — and malaria infection did not have a consistent impact on antibody levels in mothers or infants.
“HIV infection and malaria are prevalent in sub-Saharan Africa; maternal HIV infection and placental malaria have been associated with impaired transplacental transfer of maternal antibodies against a number of vaccine-preventable diseases, including tetanus, measles and Streptococcus pneumoniae,” Antonia Ho, MBChB , PhD, a clinical senior lecturer and consultant in infectious diseases in the Center for Virus Research at the University of Glasgow, and colleagues wrote in Open Forum Infectious Diseases. “HIV-infected pregnant women are an important target group for influenza vaccination since HIV-infected adults and pregnant women have greater risk for severe influenza, while the impact of malaria coinfection is poorly studied.”
The researchers conducted a cross-sectional study that included 454 pregnant women and their infants from two areas in southern Malawi who were never immunized against influenza. One of these areas — Blantyre — is an urban area with low malaria transmission. The other — Chikwawa — is a rural area with high malaria transmission. Pregnant women with HIV were excluded in Chikwawa, the researchers said
They analyzed antibodies against influenza A(H1N1), influenza A(H3N2) and two influenza B viruses from maternal and cord blood.
Women with HIV and their infants had lower seropositivity against H1N1 compared with woman who were not infected with HIV (hemagglutination inhibition titer 1:40; mothers: 24.3% vs. 45.4%; P = .02; infants: 24.3% vs. 50.5%; P = .003). Women with HIV and their infants also had lower seropositivity against H3N2 (mothers: 37.8% vs. 63.9%; P = .003; infants: 43.2% vs. 64.8%; P = .01).
According to the researchers, malaria had “an inconsistent effect on maternal and infant seropositivity.” In the Chikwawa group, women with placental malaria had lower seropositivity (78.7% vs. 91.1%; P = .02) and geometric mean (GM) titers (121.7 vs. 239.2%; GM ratio = 0.51; 95% CI, 0.32-0.8) against H1N1. However, this relationship was not reported for any other strains or for their infants.
Ho and colleagues proposed two possible explanations for why mothers with HIV may have had lower antibody responses against influenza: they generate weaker humoral responses to influenza virus infection than mothers without HIV, and they avoid crowded areas, lessening their risk for infection.
“These findings suggest influenza vaccines targeting pregnant women may have variable efficacy in sub-Saharan Africa, where up to 35% of women of childbearing age may be HIV infected,” the researchers wrote. “Adjuvanted preparations or higher doses to boost maternal antibodies may be required to optimize protection to HIV-infected pregnant women and their infants, which will impact the cost-effectiveness of maternal influenza immunization interventions.” – by Katherine Bortz
Disclosures: The authors report no relevant financial disclosures.