Perfluorooctanoic acid (PFOA) has been associated with various health effects, including immunotoxicity. This study aimed to examine associations between PFOA serum levels above the intervention threshold level (HBM-II, 10 µg/L) and diphtheria, tetanus and SARS-CoV-2 antibody concentrations among adult residents with increased internal PFOA. A total of 662 questionnaire data points and vaccination passports were collected and blood samples were used to determine PFOA serum levels and diphtheria, tetanus and SARS-CoV-2 antibody concentrations. Logistic regression modelling was used to examine potential associations. The median PFOA concentration was 9.17 µg/L with 45.2% exceeding the HBM-II. Of participants with at least one vaccination, 48.1% had reliable protection against diphtheria and 91.9% against tetanus. Antibodies against SARS-CoV-2 spike and nucleocapsid protein were detected in 96.4% and 53.8%, respectively. Age was a significant predictor for lack of immunity against diphtheria (OR = 3.6 (95% CI: 2.3; 5.7)) in the age group ≥60. No association was found between PFOA levels and SARS-CoV-2 N antibody concentrations. After adjusting for age group, PFOA serum concentrations above the intervention threshold were not associated with lower diphtheria or SARS-CoV-2 N antibody concentrations in the adult population. Further studies are needed to determine whether PFOA exposure has a long-term effect on the immune system.

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The role of perfluorooctanoic acid (PFOA) on antibody titres following vaccination in adults is not heterogeneous. High levels of anti-spike IgG have been reported following mRNA-based vaccinations. This study aimed to explore the association between PFOA exposure and exposure to SARS-CoV-2 antigen on SARS-CoV-2 anti-spike antibodies, particularly on the IgG subclasses in adult residents with increased internal PFOA exposure due to past PFOA drinking water contamination. A self-administered questionnaire was completed, and vaccination data was checked against the vaccination passport. PFOA concentration and IgG subclass titres were analysed in serum. Most study participants had three vaccinations (518; 78.6%). IgG was dominated by IgG4, a subclass that is largely unable to activate effector responses, for 8.3% of the participants, and only in the group of participants with three vaccinations. A generalised linear model was used to assess the relationship between PFOA serum concentration and IgG subclasses. After adjusting for age, a significant positive association was found between the number of vaccinations, self-reported infections and higher IgG subclasses concentrations. Age and PFOA concentration did not show a significant association with the concentration of any IgG subclass. Thus, the internal PFOA exposure was not associated with impaired immune response with regard to anti-spike SARS-CoV-2 IgG.