With a 95% efficacy rate in preventing symptomatic SARS-CoV-2 infection 7 to 14 days after the second dose, the two mRNA vaccines available in Switzerland show promise in slowing the spread of the pandemic.
Pregnant women are now clearly identified as a vulnerable population. They are more likely to become infected with SARS-CoV-2 and are at greater risk of developing severe disease than women of the same age. However, their access to vaccination remains limited due to a lack of data.
While the FOPH initially excluded pregnant women from the vaccination campaign, those who are at particularly high risk now have access to it. To receive the vaccine, they must provide informed consent after discussing the benefits and risks with their doctor.1 However, as is often the case, pregnant women have been excluded from clinical trials. This constitutes off-label prescribing, for which the prescribing physician bears full responsibility.
mRNA Vaccines
Preliminary work on a vaccine against SARS-CoV-1 and MERS paved the way for the development of vaccines against SARS-CoV-2.
In Switzerland, the two available vaccines are mRNA vaccines (Pfizer and Moderna). The mRNA vaccine is encapsulated in a lipid droplet, which allows it to fuse with the cell surface and enter the cell. The machinery used for the translation and production of the target protein—which is capable of inducing an immune response—is located outside the nucleus. This mRNA does not come into contact with the patient’s DNA, and these vaccines do not contain adjuvants.
The main reported side effects are local and systemic, such as pain and redness at the injection site or flu-like symptoms. They are usually mild and resolve within 2 days of vaccination. Anaphylactic reactions remain rare (5 per 1 million doses for Pfizer and 2.8 per 1 million doses for Moderna).
What data are available regarding vaccination during pregnancy ?
The initial available data come from animal studies and accidental exposure to the vaccines during clinical trials conducted by the pharmaceutical industry.
Animal studies show that mRNA vaccines are neither teratogenic nor fetotoxic.2
Preliminary studies conducted by the pharmaceutical industry report 36 cases of pregnant women who were accidentally vaccinated (Pfizer/Moderna) or assigned to the control group. The risk of miscarriage is the same, or even lower, in the vaccinated group.2
In a small cohort, the vaccine response during pregnancy (n=84) and breastfeeding (n=31) appears to be comparable to that observed in non-pregnant women (n=16). Furthermore, when compared to a group of patients who had contracted SARS-CoV-2 during pregnancy, the post-vaccination immune response was more robust than the natural immunity following SARS-CoV-2 infection during pregnancy.
From this cohort, data from only 13 patients who had given birth could be analyzed. Vaccine-induced antibodies were detected in umbilical cord blood and breast milk, suggesting a transfer of immunity to the newborn.3
Since the start of the vaccination campaign, the United States has vaccinated pregnant women who wished to be vaccinated. More than 94,000 patients reported being pregnant at the time of vaccination in the Center for Disease Control and Prevention’s registry (V-safe After Vaccination Health Checker). To date, data from 827 vaccinated patients (primarily in the third trimester) who have given birth have been published. No increase in obstetric risks has been observed. Side effects are similar to those seen in the general population and were not observed at an increased rate.4
A pharmaceutical industry-sponsored randomized, placebo-controlled trial on the safety and immunogenicity of the mRNA vaccine during pregnancy began in February 2021 (Pfizer/BioNTech, ClinicalTrials.gov Identifier: NCT04754594).
Recommendations from the FOPH and the SSGO
Several expert societies recommend vaccination for all pregnant women (ACOG, SMFM, RCOG, CDC). For the time being, the FOPH and the SSGO recommend vaccination during the second and third trimesters of pregnancy only for high-risk pregnant women (women with one of the chronic conditions defined for individuals vulnerable to COVID-19) and, as of April 14, 2021, also for those at increased risk of exposure to COVID-19 (particularly healthcare workers). (See the article from the Swiss Society of Gynecology and Obstetrics)
The gynecologist must conduct an informational discussion with the patient regarding the benefits, drawbacks, and risks of vaccination. The gynecologist must also obtain the patient’s signed consent and provide her with a written prescription so she can receive the vaccine. It is important to monitor potential adverse effects of the vaccine. A follow-up form must be completed and sent to the CHUV COVID registry (email: covipreg@chuv.ch). Adverse effects must also be reported to SwissMedic.
It should be noted that if the vaccine was administered by mistake during the first trimester of pregnancy, this is not an indication for termination of pregnancy. Furthermore, the vaccine can be administered to breastfeeding women without restrictions.
Should low-risk patients who wish to be vaccinated be denied the vaccine ?
Given international recommendations—and particularly those from our neighboring countries—to vaccinate all pregnant women, many women without additional risk factors are coming to the office requesting the vaccine. Considering that they are part of the vulnerable population and that we have an effective vaccine available in sufficient quantities—one whose passive immunity could also benefit the unborn child—can we refuse to sign their prescription?
In our opinion, each obstetrician-gynecologist, after conducting an informational discussion on the risks and benefits of the vaccine with a pregnant woman who wishes to be vaccinated, is in a position to decide whether to sign the prescription.
Written by:
Dr. med., MSc Agnès Ditisheim, specialist in general internal medicine and maternal medicine, Center for Fetal-Maternal Medicine at La Tour Hospital
Dr. med. Nicole Jastrow Meyer, specialist in gynecology and obstetrics, with a specialty in fetal-maternal medicine, Center for Fetal-Maternal Medicine at La Tour Hospital
References
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Rasmussen, S. et al. Coronavirus Disease 2019 (COVID-19) Vaccines and Pregnancy, What Obstetricians Need to Know, Obstetrics & Gynecology: March 2021 - Volume 137 - Issue 3 - p 408-414 doi: 10.1097/AOG.0000000000004290
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Male, V. Are COVID-19 vaccines safe in pregnancy?. Nat Rev Immunol 21, 200–201 (2021). https://doi.org/10.1038/s41577-021-00525-y
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Kathryn J. et al. COVID-19 vaccine response in pregnant and lactating women: a cohort study, Am J Obstet Gynecol 2021 Mar 24;S0002-9378(21)00187-3. doi: 10.1016/j.ajog.2021.03.023.Online ahead of print.
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Shimabukuro TT, et al. CDC v-safe COVID-19 Pregnancy Registry Team. Preliminary Findings of mRNA Covid-19 Vaccine Safety in Pregnant Persons. N Engl J Med. 2021 Apr 21. doi: 10.1056/NEJMoa2104983. Epub ahead of print. PMID: 33882218.