LBODP093 Evaluation Of The Impact Of Covid-19 Vaccines On Thyroid Function And Autoimmunity And The Potential Influence Of Pre-existing Thyroid Autoimmunity On Neutralizing Antibody Responses
Authors: Lui David , Lee Chi H , Cheung Chloe , Cheung Venus , Mak Jimmy , Fong Carol , Lui Brian , Chow Wing Sun , Lee Alan , Tam Anthony , Pang Polly , Ho Tip Yin , Tan Kathryn , Woo Yu Cho , Hung Ivan , Lam Karen 
Published: November 2022

Abstract

Objectives
There are concerns for COVID-19 vaccination in causing thyroid dysfunction and triggering thyroid autoimmunity. Also, data on the impact of pre-existing thyroid autoimmunity on COVID-19 vaccination efficacy are limited. We evaluated the impact of COVID-19 vaccination on thyroid function and antibodies, and the influence of pre-existing thyroid autoimmunity on neutralizing antibody (NAb) responses.

Methods
Adults without history of COVID-19 or thyroid disorders who received COVID-19 vaccination between 14 June 2021 and 8 August 2021 at three vaccination centers were recruited. All participants received two doses of vaccines. Thyroid-stimulating hormone (TSH), free thyroxine (fT4), free triiodothyronine (fT3), anti-thyroid peroxidase (anti-TPO) and anti-thyroglobulin (anti-Tg) antibodies were measured at baseline and 8 weeks after the first dose of vaccination. Post-vaccination NAb against SARS-CoV-2 receptor-binding domain was measured.

Results
In total, 215 individuals were included (129 BNT162b2 [60%] and 86 CoronaVac [40%] recipients): mean age 49.6 years, 37.2% men, and 12.1% positive for anti-TPO/anti-Tg at baseline. After vaccination, TSH levels did not change (p=0.225), but fT4 slightly increased (from 12. 0±1.1 to 12.2±1.2 pmol/L, p&lt;0. 001) and fT3 slightly decreased (from 4.1±0.4 to 4. 0±0.4 pmol/L, p&lt;0. 001). Only 3 patients (1.4%) had abnormal thyroid function after vaccination: two occurred among BNT162b2 recipients - both were subclinical thyrotoxicosis (TSH 0.32mIU/L, fT4 11.51pmol/L and fT3 4.40pmol/L; TSH 0.34mIU/L, fT4 12.67pmol/L and fT3 4.22pmol/L; both were anti-TPO and anti-Tg negative before and after vaccination); one occurred among CoronaVac recipients - isolated mild low fT3 (TSH 0.90mIU/L, fT4 9.94pmol/L and fT3 2.33pmol/L; anti-TPO/Tg negative before and after vaccination). All three recipients were asymptomatic. Both anti-TPO and anti-Tg titers increased modestly after vaccination (anti-TPO: from 7.50 [IQR: 5.90-11.2] to 9.80 IU/mL [IQR: 7.80-13.1], p&lt;0. 001; anti-Tg: from 12.4 [IQR: 11.1-14.9] to 15.7 IU/mL [IQR: 14.2-18.2], p&lt;0. 001), without significant changes in anti-TPO/Tg positivity. Changes in thyroid function and anti-thyroid antibodies were generally consistent between BNT162b2 and CoronaVac recipients, although anti-TPO titer rise was greater after BNT162b2 (p&lt;0. 001). NAb responses were similar between individuals with and without pre-existing thyroid autoimmunity (p=0.855).

Conclusion
COVID-19 vaccination was associated with a modest increase in anti-thyroid antibody titers. Anti-TPO increase was greater among BNT162b2 recipients. However, there was no clinically significant thyroid dysfunction 8 weeks post-vaccination. NAb responses were not influenced by pre-existing thyroid autoimmunity. Our results provided important reassurance to people to proceed to COVID-19 vaccination.
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