Impact of inoculation of inactivated COVID-19 vaccine on the outcomes of frozen-thawed embryo transfer

Abstract To assess the impact of inoculation of inactivated corona virus disease 2019 (COVID-19) vaccine on the outcome of frozen-thawed embryo transfer (FET). From January 2022 to November 2023, patients aged 20 ~ 45 years old undergoing FET at the Reproductive Medicine Center of a tertiary teaching hospital were prospectively enrolled. The patients were divided into vaccinated group (n = 458) and unvaccinated group (n = 530) based on the inoculation of inactivated COVID-19 vaccine before FET. Vaccinated group was further divided into three subgroups based on the dose (single dose, n = 55; double dose, n = 292; triple dose, n = 111) or interval from the first inoculation to FET (< 3 months, n = 51; 3 ~ 6 months, n = 101; > 6 months, n = 306). The primary outcome was live birth rate (LBR). The LBR (43.87% vs. 40.57%) was not significantly different between the vaccinated and unvaccinated groups, and so were embryo implantation rate (IR), clinical pregnancy rate (CPR), the gestational age at delivery and birth weight (P > 0.05). IR was significantly decreased with the shorter interval of vaccination (28.57% vs. 32.02% vs.45.24%, P = 0.007), while LBR and CPR were not significantly different (P > 0.05). For the dose subgroups of vaccination, IR, LBR and CPR were not significantly different (P > 0.05). Inoculation of inactivated COVID-19 vaccine did not affect the outcome of FET. Clinical Trial Registration Number: ChiCTR2200055597 (Chinese Clinical Trial Registry), January 14, 2022. (https://www.chictr.org.cn/bin/project/edit?pid=148312)