ABSTRACT
BACKGROUND: In view of accumulating case reports of thyroid dysfunction following COVID-19 vaccination, we evaluated the risks of incident thyroid dysfunction following inactivated (CoronaVac) and mRNA (BNT162b2) COVID-19 vaccines using a population-based dataset. METHODS: We identified people who received COVID-19 vaccination between 23 February and 30 September 2021 from a population-based electronic health database in Hong Kong, linked to vaccination records. Thyroid dysfunction encompassed anti-thyroid drug (ATD)/levothyroxine (LT4) initiation, biochemical picture of hyperthyroidism/hypothyroidism, incident Graves' disease (GD), and thyroiditis. A self-controlled case series design was used to estimate the incidence rate ratio (IRR) of thyroid dysfunction in a 56-day post-vaccination period compared to the baseline period (non-exposure period) using conditional Poisson regression. RESULTS: A total of 2,288,239 people received at least one dose of COVID-19 vaccination (57.8% BNT162b2 recipients and 42.2% CoronaVac recipients). 94.3% of BNT162b2 recipients and 92.2% of CoronaVac recipients received the second dose. Following the first dose of COVID-19 vaccination, there was no increase in the risks of ATD initiation (BNT162b2: IRR 0.864, 95% CI 0.670-1.114; CoronaVac: IRR 0.707, 95% CI 0.549-0.912), LT4 initiation (BNT162b2: IRR 0.911, 95% CI 0.716-1.159; CoronaVac: IRR 0.778, 95% CI 0.618-0.981), biochemical picture of hyperthyroidism (BNT162b2: IRR 0.872, 95% CI 0.744-1.023; CoronaVac: IRR 0.830, 95% CI 0.713-0.967) or hypothyroidism (BNT162b2: IRR 1.002, 95% CI 0.838-1.199; CoronaVac: IRR 0.963, 95% CI 0.807-1.149), GD, and thyroiditis. Similarly, following the second dose of COVID-19 vaccination, there was no increase in the risks of ATD initiation (BNT162b2: IRR 0.972, 95% CI 0.770-1.227; CoronaVac: IRR 0.879, 95%CI 0.693-1.116), LT4 initiation (BNT162b2: IRR 1.019, 95% CI 0.833-1.246; CoronaVac: IRR 0.768, 95% CI 0.613-0.962), hyperthyroidism (BNT162b2: IRR 1.039, 95% CI 0.899-1.201; CoronaVac: IRR 0.911, 95% CI 0.786-1.055), hypothyroidism (BNT162b2: IRR 0.935, 95% CI 0.794-1.102; CoronaVac: IRR 0.945, 95% CI 0.799-1.119), GD, and thyroiditis. Age- and sex-specific subgroup and sensitivity analyses showed consistent neutral associations between thyroid dysfunction and both types of COVID-19 vaccines. CONCLUSIONS: Our population-based study showed no evidence of vaccine-related increase in incident hyperthyroidism or hypothyroidism with both BNT162b2 and CoronaVac.
Subject(s)
COVID-19 Vaccines , COVID-19 , Hyperthyroidism , Hypothyroidism , Female , Humans , Male , BNT162 Vaccine , COVID-19/epidemiology , COVID-19/prevention & control , COVID-19 Vaccines/adverse effects , Hyperthyroidism/chemically induced , Hyperthyroidism/epidemiology , Hypothyroidism/chemically induced , Hypothyroidism/epidemiology , RNA, Messenger , Thyroxine , VaccinesABSTRACT
Background: Thyroiditis and Graves' disease have been reported after coronavirus disease 2019 (COVID-19) vaccination. We evaluated the risks of adverse events after COVID-19 vaccination among patients treated for hypothyroidism. Methods: In this retrospective population-based cohort study of Hong Kong Hospital Authority electronic health records with the Department of Health vaccination records linkage, levothyroxine (LT4) users were categorized into unvaccinated, vaccinated with BNT162b2 (mRNA vaccine), or CoronaVac (inactivated vaccine) between February 23, 2021, and September 9, 2021. Study outcomes were dosage reduction or escalation in LT4, emergency department (ED) visit, unscheduled hospitalization, adverse events of special interest (AESI) according to the World Health Organization's Global Advisory Committee on Vaccine Safety, and all-cause mortality. Inverse probability of treatment weighting for propensity score was applied to balance baseline patient characteristics among the three groups. Hazard ratios (HR) were estimated using Cox regression models. Patients were observed from the index date until the occurrence of study outcome, death, or censored on September 30, 2021, whichever came first. Results: In total, 47,086 LT4 users were identified (BNT162b2: n = 12,310; CoronaVac: n = 11,353; and unvaccinated: n = 23,423). COVID-19 vaccination was not associated with increased risks of LT4 dosage reduction (BNT162b2: HR = 0.971 [confidence interval; CI 0.892-1.058]; CoronaVac: HR = 0.968 [CI 0.904-1.037]) or escalation (BNT162b2: HR = 0.779 [CI 0.519-1.169]; CoronaVac: HR = 0.715 [CI 0.481-1.062]). Besides, COVID-19 vaccination was not associated with a higher risk of ED visits (BNT162b2: HR = 0.944 [CI 0.700-1.273]; CoronaVac: HR = 0.851 [CI 0.647-1.120]) or unscheduled hospitalization (BNT162b2: HR = 0.905 [CI 0.539-1.520]; CoronaVac: HR = 0.735 [CI 0.448-1.207]). There were two (0.016%) deaths and six (0.062%) AESI recorded for BNT162b2 recipients, and one (0.009%) and three (0.035%) for CoronaVac recipients, respectively. Conclusions: BNT162b2 or CoronaVac vaccination is not associated with unstable thyroid status or an increased risk of adverse outcomes among patients treated for hypothyroidism in general. These reassuring data should encourage them to get vaccinated against COVID-19 for protection from potentially worse COVID-19-related outcomes.