COVID-19 vaccination advice upgraded yet again for those pregnant or planning pregnancy

Published 01 September 2021

With studies continuing to find no detrimental reproductive or pregnancy effects of COVID-19 vaccination, agencies and investigators have stepped up their recommendations in its favour.

In August the US Centers for Disease Control and Prevention (CDC) upgraded its COVID-19 vaccine advice for women who are or aiming to be pregnant.(1) The update came with two thrusts: first that the benefits of having the vaccine ‘outweigh any known or potential risks of vaccination during pregnancy’; and secondly that pregnant and recently pregnant women are at a higher risk of severe illness from COVID-19 than non-pregnant. The CDC also reaffirms the safety record of the vaccines and reiterates reports that antibodies have been found in umbilical cord blood and in breast milk – which may, says the CDC, ‘help protect their babies’.(2,3) As noted in a recent FoR report, other agencies, including the UK’s Royal College of Obstetricians and Gynaecologists, have also upgraded their vaccination advice in pregnancy.(4)

Exploring the epidemic of vaccine myths involving COVID-19 and pregnancy, the magazine Scientific American sought expert opinions and questioned the much reported fake news (of apparently German origin in a message to the European Medicine Agency, EMA) that the vaccine may cause sterility in women.(5) The speculated mechanism was the presumed similarity between the SARS-CoV-2 spike protein and a protein known as syncytin-1, a protein that is critical to the formation of a developing embryo. The social media hypothesis was thus that immune cross-reactivity (following vaccination) would result in damage to the developing trophoblast, thereby preventing embryo implantation. In June this year the misinformation was reality-checked in a series of frozen embryo transfers in vaccine seropositive, infection seropositive and seronegative women.(6) No difference was found in serum hCG-documented implantation rates or sustained implantation rates between the three groups. ‘Physicians and public health personnel can counsel women of reproductive age that neither previous illness with COVID-19 nor antibodies produced from vaccination to COVID-19 will cause sterility,’ the author concluded emphatically.

Meanwhile, an August report from the EMA’s Pharmacovigilance Risk Assessment Committee, discussing cases of menstrual disorders reported after COVID-19 vaccination, found ‘no causal association between COVID-19 vaccines and menstrual disorders’, attributing such ‘common’ symptoms to stress, tiredness, and underlying conditions such as fibroids and endometriosis.(7)

Concerns for male infertility as a result of infection were originally inspired by the finding that men generally appeared to be more severely affected than women. Although mainly affecting the lungs, where there is an increased expression of angiotensin-converting enzyme (ACE-2) receptors (to which COVID-19 has a high affinity for binding and subsequent entry), the ACE-2 receptor is also widely expressed in the testes. With this in mind, there has been some evidence that the male reproductive tract, specifically the testes, may be targets of COVID-19 infection. One study reported earlier this year found an inverse association between ACE-2 receptor levels and spermatogenesis, suggesting a possible mechanism of how COVID-19 may cause infertility.(8) However, results of an effect of infection or vaccination on male fertility have been variable, and a more recent study of sperm parameters before and after two doses of a mRNA vaccine found no significant decreases in any sperm parameter among a small cohort of healthy men.(9) Because the vaccines studied contain mRNA and not the live virus, the authors concluded ‘it is unlikely that the vaccine would affect sperm parameters’.

As the reassuring data against any detrimental effect of COVID-19 vaccination grow, the message from authorities now seems to be – as reflected in the CDC’s latest report – that infection in pregnancy or ahead of pregnancy is associated with a far greater risk of complications than vaccination. As the Scientific American feature concluded: ‘The key to protecting against the reproductive and sexual effects of COVID-19 is to get vaccinated.’

1. See
2. Gray KJ, Bordt EA, Atyeo C, et al. Coronavirus disease 2019 vaccine response in pregnant and lactating women: a cohort study. Am J Obstet Gynecol 2021.
3. Perl SH, Uzan-Yulzari A, Klainer H, et al. SARS-CoV-2–specific aAntibodies in breast milk after COVID-19 vaccination of breastfeeding women. JAMA 2021; 325: 2013–2014. doi:10.1001/jama.2021.5782
4. See
5. See
6. Morris RS. SARS-CoV-2 spike protein seropositivity from vaccination or infection does not cause sterility. Fertil Steril Rep 2021;
7. See
8. Achua JK, Chu KY, Ibrahim E, et al.
Histopathology and ultrastructural findings of fatal COVID-19 infections on testis. World J Mens Health 2021; 39: 65-74.
9. Gonzalez DC, Nassau DE, Khodamoradi K, et al. Sperm parameters before and after COVID-19 mRNA vaccination. JAMA 2021; 326: 273-274. doi:10.1001/jama.2021.9976

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