Risk of thyroid dysfunction after COVID-19 vaccination: meta-analysis of 11 million individuals.

BACKGROUND

To mitigate the SARS-CoV-2 pandemic, the worldwide rollout of COVID-19 vaccinations has been essential. Potential links between the COVID-19 vaccine and several thyroid disorders, like subacute thyroiditis, Graves' disease, and thyroiditis, were shown by early case reports and short observational studies. The goal of this systematic review and meta-analysis is to assess the relationship between several COVID-19 vaccinations and thyroid conditions.

METHODS

We conducted a comprehensive search of major databases through February 2025, adhering to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) criteria. Thyroid dysfunction after COVID-19 vaccination was the main outcome measure used in our analysis of 21 studies. Specific thyroid dysfunctions (Graves' disease, hyperthyroidism, hypothyroidism, thyroiditis, and thyroid eye disease) were among the secondary outcomes. For every meta-analysis, we used random-effects models based on the Der Simonian and Laird approach, considering the anticipated clinical and methodological heterogeneity among trials.

RESULTS

Single-arm meta-analysis revealed thyroid dysfunction prevalence of 8.54% [95% confidence interval (CI) 3.45-19.61%] among vaccinated individuals compared to 31.78% (95% CI: 14.18-56.79%) in unvaccinated populations (P = 0.026) with significantly lower prevalence of Graves' disease among vaccinated individuals (8.55 vs. 46.50%, P = 0.045; relative risk (RR) = 0.18, 95% CI: 0.04-0.92). Hyperthyroidism (1.11 vs. 1.55%, P = 0.90), hypothyroidism (1.13 vs. 5.13%, P = 0.44), and thyroiditis (0.26 vs. 3.90%, P = 0.49) showed no significant differences between vaccination groups; however, new-onset hyperthyroidism demonstrated significantly higher prevalence in vaccinated individuals (0.24 vs. 0.13%, P < 0.001; RR = 1.85, 95% CI: 1.84-1.86).

CONCLUSION

This thorough meta-analysis offers comforting proof of the COVID-19 vaccines' safety for the thyroid, with some protective benefits against Graves' disease and mostly neutral relationships with other thyroid conditions.