COVID-19 vaccination survey and anti-SARS-CoV-2 S1 IgG responses in a human cohort from Schistosoma mansoni-endemic villages in Mayuge, Uganda: A cross-sectional study

Introduction: Coronavirus disease 2019 (COVID-19) pandemic precipitated devastating health and economic consequences globally. Vaccination has been a central pillar for COVID-19 prevention and control. Understanding the immunomodulatory effects of helminth infections on COVID-19 vaccine-induced immune responses and vaccine efficacy is crucial to the development and deployment of effective vaccination strategies in low- and middle-income countries with high prevalence of worms. Methods: In September 2022, we conducted a cross-sectional, population-based survey in five Schistosoma mansoni endemic villages in Mayuge District, Uganda (n=450). The prevalence of schistosomiasis and soil-transmitted helminths was determined by the Kato-Katz (KK) technique on two stool samples collected from each participant. A subset of individuals (n=204) were interviewed in a COVID-19 vaccination survey. IgG levels against the SARS-CoV-2 spike S1 subunit (Anti-S1 IgG) were measured by enzyme-linked immunosorbent assay (ELISA) assays using collected serum samples. Results: The overall schistosomiasis and hookworm prevalence in the five villages was 36.4% (166/450) and 36.9% (168/450), respectively. Within the cohort, 69.78% (314/450) subjects showed a positive anti-S1 IgG response. COVID-19 vaccination coverage in interviewed participants was 93.14% (190/204; 95% CI, 88.8% − 95.9%). However, 81% (154/190) COVID-19 vaccinees had an anti-S1 IgG titer ≤ 200. In an adolescent group receiving a single dose of BNT162b2 vaccine (n=23), an inverse correlation was observed between anti-S1 IgG antibody levels/titers and faecal egg counts. Within the above group, anti-S1 IgG levels/titers were significantly low in subjects with a moderate-to-heavy S. mansoni infections (n=5) compared with KK-negative individuals (n=9). IgG1 was the dominant IgG subclass in sub-groups vaccinated with a single dose of the BNT162b2 (n=23) or Ad26.COV2.S (n=18). Conclusion : Although the acceptance rate of COVID-19 vaccination was high, the majority of participants received only a single vaccine dose and the overall anti-S1 IgG titers in confirmed vaccinees were low. Moderate-to-heavy intensity schistosome infections blunted the antibody response following vaccination with a single dose of BNT162b2. These observations confirm the necessity for a second vaccine dose for two-dose primary immunization series and call for implementation research that may inform the development of a ‘treat and vaccinate’ policy during vaccination roll-out in regions with heavy worm burdens.