Thyroiditis Should be Listed Among Adverse Effects of Covid-19 Vaccination

Background: Several cases of thyroiditis were recently reported in individuals vaccinated against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus causing coronavirus disease 2019 (COVID-19). Objective: To determine characteristics of thyroiditis occurring following SARS-CoV-2 vaccination. Methods: PubMed search up to April 26, 2022. Search terms are thyroiditis, SARS-Cov-2, vaccine, COVID-19. Case reports, case series, review articles and pertinent in vitro studies in English, Spanish and French are reviewed. Results: Review of literature revealed 97 patients with thyroiditis (71.3% women, age range 26-82 year-old) occurring following vaccination against SARS-CoV-2. Subjects reported from Turkey alone contributed to 50.5% of all cases. Seven cases (7.2%) presented with silent (painless) thyroiditis. Onset of thyroiditis symptoms ranged from 12 hours to 12 weeks after vaccination. In 74.2% of patients, these symptoms started between 3 to 15 days post-vaccination. The most frequently implicated vaccine was Pfizer-BioNTech vaccine (55.7% of cases) followed by CoronaVac (21.6%), Moderna (8.5%) and AstraZeneca (6.1%). Thyroiditis cases were equally triggered after the first and second vaccine dose. Personal and family history of thyroid diseases and autoimmune diseases were uncommon (<5%). Among 7 patients who were re-vaccinated, 5 did not have relapse of thyroiditis, whereas 2 subjects had recurrence or worsening of thyroiditis symptoms. Clinical picture and course of thyroiditis induced by the vaccine generally mimic those of non-vaccine-related classic thyroiditis. Mechanisms of thyroiditis after COVID-19 vaccination are unclear but there is evidence of genetic predisposition related to specific human leukocyte antigens (HLA) haplotypes. Glucocorticoid therapy of thyroiditis may virtually decrease COVID-19 vaccine immunogenicity. Conclusion: Thyroiditis should be listed among adverse effects of COVID-19 vaccines to alert physicians and avoid misdiagnosis and unnecessary investigations. If possible, it may be better to avoid its treatment with glucocorticoids.