Study question: Do inactivated coronavirus disease-2019 (COVID-19) vaccines affect IVF outcomes among the vaccine recipients?

Summary answer: The receipt of inactivated COVID-19 vaccines before ovarian stimulation has little effect on the outcomes of IVF, including ovarian stimulation outcomes, embryo development and pregnancy rates.

What is known already: Limited studies have reported that COVID-19 vaccines do not affect ovarian function, embryo development or pregnancy outcomes.

Study design, size, duration: This was a retrospective cohort study performed at the Third Affiliated Hospital of Guangzhou Medical University on 240 women vaccinated with either CoronaVac or Sinopharm COVID-19 before ovarian stimulation in the exposed group and 1343 unvaccinated women before ovarian stimulation in the unexposed group. All participants received fresh embryo transfers between 1 March 2021 and 15 September 2021. The included women were followed up until 12 weeks of gestation.

Participants/materials, setting, methods: Vaccination information of all subjects was followed up by a nurse, and the IVF data were obtained from the IVF data system. The following aspects were compared between the vaccinated and the unvaccinated groups: parameters of ovarian stimulation, embryo development and pregnancy rates. Regression analyses were performed to control for confounders of embryo development and pregnancy rates. Propensity score matching (PSM) was performed to balance the baseline parameters of the two groups. The primary outcome was the ongoing pregnancy rate.

Main results and the role of chance: Liner regression analysis revealed that the number of oocytes retrieved (regression coefficient (B) = -0.299, P = 0.264), embryos suitable for transfer (B = -0.203, P = 0.127) and blastocysts (B = -0.250, P = 0.105) were not associated with the status of vaccination before ovarian stimulation, after adjusting for the confounders. The ongoing pregnancy rate in the women of the vaccinated group was not significantly lower than that in the unvaccinated group (36.3% vs 40.7%, P = 0.199) (adjust odd ratio = 0.91, 95% CI = 0.68-1.22, P = 0.52). After PSM, the rates of ongoing pregnancy (36.0% vs 39.9%, P = 0.272), implantation (35.4% vs 38.3%, P = 0.325), biochemical pregnancy (47.3% vs 51.6%, P = 0.232), clinical pregnancy (44.4% vs 47.4%, P = 0.398) and early miscarriage (15.0% vs 12.1%, P = 0.399) were not significantly different between the vaccinated and the unvaccinated groups.

Limitations, reasons for caution: This is a retrospective study of women with infertility. The results from the present study warrant confirmation by prospective studies with a larger cohort.

Wider implications of the findings: This is the first study with a large sample size on the effect of inactivated COVID-19 vaccines on ongoing pregnancy rates of women undergoing IVF. The present results showed that vaccination has no detrimental effect on IVF outcomes. Therefore, women are recommended to receive COVID-19 vaccines before undergoing their IVF treatment.

Study funding/competing interest(s): This study was supported by the National Key Research and Development Program of China (No. 2018YFC1003803 to J.L.), the Guangzhou Science and Technology Plan Project (No. 202102010076 to H.L.) and the Medical Key Discipline of Guangzhou (2021-2023), as well as the Sino-German Center for Research Promotion Rapid Response Funding Call for Bilateral Collaborative Proposals between China and Germany in COVID-19 Related Research (No. C-0032 to Xingfei Pan). The authors declare no conflicts of interest.

Trial registration number: N/A.