Association between helminth infection and impaired SARS-CoV-2 antibody responses following COVID-19 vaccination: a cross-sectional study in Malawi.

Chronic helminth infections can modulate immune responses to infection and vaccination. This study explored the association between current helminth infection, including waterborne and soil-transmitted helminths (STHs), and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) neutralising and IgG antibody responses. Samples were collected cross-sectionally from participants across rural (Karonga) and urban (Lilongwe) regions in Malawi. Helminth infections were detected via real-time PCR in stool and urine samples, targeting Schistosoma spp., Ascaris lumbricoides, Ancylostoma duodenale, Necator americanus, and Trichuris trichiura. SARS-CoV-2 nAbs were measured using a human immunodeficiency virus (HIV)-based pseudotyped virus neutralisation assay. A nucleocapsid (N) protein enzyme-linked immunosorbent assay (ELISA) identified prior natural SARS-CoV-2 infection in vaccinated participants. IgG targeting the spike (S) protein was measured using an ELISA. Helminth infection was found to be associated with reduced nAb responses post coronavirus disease 2019 (COVID-19) vaccination, but not after natural SARS-CoV-2 infection. Generalised additive model analysis confirmed this interaction while considering covariates. IgG responses were also impaired among those helminth-infected. It should be investigated whether integrating pre-vaccination deworming improves vaccine responses in helminth-endemic regions.