SARS-CoV-2 vaccine-associated subacute thyroiditis: insights from a systematic review

Abstract

Purpose: To 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.

Methods: Original 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.

Results: 30 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.

Conclusion: SARS-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.

Keywords: Adjuvants; SARS-CoV-2; Subacute thyroiditis; Thyroid; Vaccine.

Fig. 1

Thyroid ultrasound and scintigraphy in SARS-CoV-2 post-vaccination SAT. Ultrasound performed a at diagnosis and b at resolution of symptoms in a patient with subacute thyroiditis developed after mRNA vaccine for SARS-CoV-2 (Case 1, described in Table 1). At diagnosis thyroid was enlarged, highly inhomogeneous and nodular. After therapy, at resolution of symptoms, thyroid echostructure remained inhomogeneous, but thyroid volume was back to normal and there were no nodules. c Thyroid scintigraphy revealed low/absent thyroid uptake in a patient with subacute thyroiditis developed after mRNA vaccine for SARS-CoV-2 (Case 1, described in Table 1)

Fig. 2

Flow diagram. Flow diagram of recorded studies and reports, according to PRISMA 2020 flow diagram [22] for systematic reviews

Fig. 3

Epidemiology, clinical, and diagnostic approach in SARS-CoV-2 post-vaccination SAT patients. a Sex prevalence and age distribution according to sex. Pie chart depicting absolute sex prevalence of reported cases; bar graph showing the relative sex prevalence for female (white bars) and male (black bars), according to four age groups: 21–35 years, 36–50 years, 51–65 years, over 65 years, at the top of each bar the absolute number is reported. p assessed with Wilcoxon rank-sum test. b Geographic distribution. 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