Response to Letter to the Editor From Kleebayoon and Wiuwanikit: “Subacute THYROiditis Related to SARS-CoV-2 Vaccine and COVID-19 (THYROVAC Study): A Multicenter Nationwide Study”

We thank Kleebayoon et al for their interest in our article (1) and would like to address the 3 points raised in their Letter to the Editor (2).

Regarding the first point, during the COVID-19 pandemic, vaccinations against COVID-19 were carried out by the National Ministry of Health of Turkey based on some inclusion/exclusion criteria and were followed-up by an application available nationwide and monitored centrally. For example, patients with symptomatic COVID-19 infection within the past 6 months and asymptomatic COVID-19 infection within the past 3 months were not candidates for vaccination before the end of these periods.

Regarding the second point, we totally agree with the authors in that without the necessary laboratory testing, it can be difficult to totally rule out a previously asymptomatic illness during the COVID-19 pandemic. To exclude the effects of possible asymptomatic COVID-19 cases on the investigated outcomes, in Cox regression analyses, the control subacute thyroiditis group solely included cases diagnosed before the COVID-19 pandemic and excluded control cases diagnosed during the pandemic.

Regarding the last point, a genetic predisposition to the development of subacute thyroiditis is present; in genetically susceptible individuals, such a predisposition may lead to subacute thyroiditis development through thyroid destruction by disrupting the immunological balance of the host. It has been reported that the risk for developing the disease in patients with HLA-Bw35 is 6-fold that of the general population (3). Also, asymptomatic SARS-CoV-2 infection is reported to be linked to the HLA allele (4). Further research is desirable to document the associations between genetic predisposition linked to COVID-19 and vaccination-associated subacute thyroiditis.

Disclosures

Kemal Ağbaht is an editorial board member for JCEM. The authors have nothing else to disclose.

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