Abstract
PurposeTo perform a systematic review on published cases of subacute thyroiditis (SAT) secondary to SARS-CoV-2 vaccination, to highlight main features and increase the awareness of this condition.MethodsOriginal reports of SAT developed after SARS-CoV-2 vaccination (mRNA, viral vector, or inactivated virus vaccines) were retrieved from a search of electronic databases. Individual patient data on demographics, medical history, type of vaccine, workup and therapies were collected. Wilcoxon rank-sum, Kruskal–Wallis and chi-squared tests were employed for comparisons.Results30 articles including 48 reports were retrieved, 3 additional cases evaluated by the Authors were described and included for analysis. Of the 51 patients, 38 (74.5%) were women, median age was 39.5 years (IQR 34–47). Patients developed SAT after a median of 10 days (IQR 4–14) after the vaccine shot. Baseline thyroid exams revealed thyrotoxicosis in 88.2% of patients, decreasing at 31.6% at follow-up. Corticosteroids were used in 56.4% of treated patients. Patients undergoing non-mRNA vaccines were most frequently Asian (p = 0.019) and reported more frequently weight loss (p = 0.021). All patients with a previous diagnosis of thyroid disease belonged to the mRNA vaccine group.ConclusionSARS-CoV-2 vaccine-associated SAT is a novel entity that should be acknowledged by physicians. Previous history of thyroid disease may predispose to develop SAT after mRNA vaccines, but further studies and larger cohorts are needed to verify this suggestion. SARS-CoV-2 vaccine-associated SAT is usually of mild/moderate severity and could be easily treated in most cases, thus it should not raise any concern regarding the need to be vaccinated.
Highlights
Subacute thyroiditis (SAT) is an inflammatory disease of the thyroid gland causing transient thyrotoxicosis, characterized by neck pain and symptoms of thyroid hormones excess
Color intensity represents the number of cases reported for that specific Country. c Prevalence of SAT symptoms in recorded cases, at the top of each bar the absolute number is reported; bullet point summarizes the timing of symptoms onset according to the vaccine dose. aThis patient received 2 doses of inactivated virus vaccine and a subsequent booster of mRNA vaccine. d Workup and main diagnostic outcomes of reported patients vary according to sex (p = 0.135) (Fig. 3a). 24 patients (47%) were European, 18 patients (35.3%) Asian, 8 (15.7%) North American and 1 (2%) Australian; Fig. 3b represents geographic distribution
History of thyroid disease was reported in 6 (11.8%) patients: 5 patients suffered from hypothyroidism under adequate substitution therapy control, of which autoimmune thyroiditis was previously diagnosed in 4 of them, and 1 patient had a history of hemithyroidectomy for a benign thyroid nodule
Summary
Subacute thyroiditis (SAT) is an inflammatory disease of the thyroid gland causing transient thyrotoxicosis, characterized by neck pain and symptoms of thyroid hormones excess. The first mechanism suggested is the autoimmune/inflammatory syndrome induced by adjuvants (ASIA) [17], an adjuvants-triggered immune reaction due to vaccine (or other drugs or products) excipients which could determine dysregulation of both innate and adaptive immune systems, possibly causing destructive thyroiditis or even new onset of autoimmune diseases such as Hashimoto’s thyroiditis [18]. A second hypothesis is linked to molecular mimicry: a recent in-vitro study [20] found that antibodies against SARS-CoV-2 proteins could cross-react with several tissue antigens, including thyroid antigens such as thyroid peroxidase (TPO). This immune crosstalk could represent a common mechanism for immune-mediated complications both after SARS-CoV-2 infections [21] and for SARS-CoV-2 vaccination
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