Background:
Per- and polyfluoroalkyl substances (PFAS) are widely used, environmentally ubiquitous, and stable chemicals that have been associated with lower vaccine-induced antibody responses in children; however, data on adults are limited. The drinking water from one of the two waterworks in Ronneby, Sweden, was heavily contaminated for decades with PFAS from firefighting foams, primarily perfluorohexane sulfonic acid and perfluorooctanesulfonic acid (PFOS). Vaccination against SARS-CoV-2 offered a unique opportunity to investigate antibody responses to primary vaccination in adults who had been exposed to PFAS.

Objectives:
Our objective was to evaluate associations between PFAS, across a wide range of exposure levels, and antibody responses in adults 5 wk and 6 months after a two-dose vaccination regime against SARS-CoV-2.

Methods:
Adults age 20–60 y from Ronneby (lowercase italic n equals 309n=309
, median PFOS serum level 47 nanograms per milliliter47 ng/mL
, fifth to 95th percentile 4 to 213 nanograms per milliliter4–213 ng/mL
) and a group with background exposure (lowercase italic n equals 47n=47
, median PFOS serum level 4 nanograms per milliliter4 ng/mL
) received two doses of the Spikevax (Moderna) mRNA vaccine. The levels of seven PFAS were measured in serum before vaccination. Serum immunoglobulin G antibodies against the SARS-CoV-2 spike antigen (S-Abs) were measured before vaccination and at 5 wk (lowercase italic n equals 350n=350
) and 6 months (lowercase italic n equals 329n=329
) after the second vaccine dose. Linear regression analyses were fitted against current, historical, and prenatal exposure to PFAS, adjusting for sex, age, and smoking, excluding individuals with previous SARS-CoV-2-infection.

Results:
PFAS exposure, regardless of how it was estimated, was not negatively associated with antibody levels 5 wk [current PFOS: negative 0.5 percent−0.5%
S-Abs/PFOS interquartile range (IQR); 95% confidence interval (CI): negative 8−8
, 7] or 6 months (current PFOS: 3% S-Abs/PFOS IQR; 95% CI: negative 6−6
, 12) after COVID-19 vaccination.

Discussion:
Following a strict study protocol, rigorous study design, and few dropouts, we found no indication that PFAS exposure negatively affected antibody responses to COVID-19 mRNA vaccination for up to 6 months after vaccination. https://doi.org/10.1289/EHP11847