Low Vitamin D Does Not Explain Poor Flu Vaccine Immunogenicity

NEW ORLEANS, LA—Vitamin D deficiency does not explain poor influenza vaccine immunogenicity among HIV-infected adults or others, according to findings from a prospective cohort study reported at IDWeek 2016.

“Vitamin D deficiency was common among both HIV+ and HIV- adults, but lower levels did not predict antibody responses after H1N1 (2009) influenza vaccination,” reported Nancy Crum-Cianflone, MD, MPH, of the Uniformed Services University of the Health Sciences in Bethesda, MD, and coauthors.

“Low 25(OH)D levels do not explain the poorer post-influenza vaccination responses among HIV+ persons,” the authors reported.

Post-vaccination antibody responses are “often inadequate,” particularly among HIV+ individuals, the authors noted. Because vitamin D deficiency is common among HIV+ adults and low 25-hydroxyvitamin D [25(OH)D] levels are associated with immune response, the authors assessed the association between 25(OH)D levels and monovalent influenza A (H1N1) vaccination responses among HIV+ and HIV- adults age 18–50 years during the 2009–2010 influenza season.

A total of 128 adult participants were enrolled in the study, half of whom were HIV+.

Participants’ antibody titers were measured with humagluttination-inhibition assays at baseline, Day 28, and 6 months after vaccination, and serum 25(OH)D levels were evaluated at Day 28. Post-vaccination seroconversion associations with 25(OH)D levels were examined in univariate and multivariate regression analyses. 25(OH)D deficiency was defined as <20ng.

“HIV+ [participants] had a median CD4 count 580 cells/mm³,” the authors reported. “Seroconversion at Day 28 post-vaccination was achieved in fewer HIV+ compared with HIV- participants (56% vs. 74%; P=0.03).  Similarly, HIV+ persons had lower GMTs at Day 28 (269 vs. 80; P=0.003) and 6 months (113 vs. 20; P=0.0002) post-vaccination.”

Vitamin D deficiency was not statistically-significantly more prevalent among HIV+ than HIV-uninfected participants (25% vs. 17%; P=0.39, n.s.), and no association was detected between 25(OH)D levels and antibody response at either Day 28 or 6 months after vaccination, among HIV+ or HIV-uninfected adults, the researchers reported. 

“Further research is needed to improve vaccine immunogenicity especially among HIV+ persons,” the authors concluded.