Must I Wait Longer for a COVID-19 Vaccine If I’m Pregnant?

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Recently, we discussed encouraging results from clinical testing of COVID-19 vaccines produced by Pfizer and BioNTech and by Moderna, vaccines consisting of a molecule of what’s called mRNA, delivered to body cells within a spherical container built of fatty substances. We then discussed encouraging results from clinical studies of the COVID-19 vaccine from AstraZeneca and Oxford University, which consists of a strip of DNA inside a virus called AAV, and we’ll be discussing still more COVID-19 vaccines as clinical trial results become available. In all cases, however, we have noted that there have not been any results specific to pregnant women. The various vaccines that look promising to be effective and available to massive amounts of people in the upcoming year are all in phases of clinical testing known as phase 2 and phase 3. Sometimes overlapped or conducted in the same study, phases 2 and 3 focus on determining how effective a vaccine is at doing what is designed to do —either stopping a disease from spreading, or at least preventing or reducing symptoms in those who do become infected. This is in contrast with phase 1, in which only the safety of a vaccine is studied (although safety continues to be studied throughout phases 2 and 3).

Despite the fact that there have been proposals to include pregnant women at least in phase 3 testing, these proposals have faced resistance and pregnant women are not near the top of the list in terms of who will be offered vaccination. Outside of pregnancy, things are moving forward with respect to COVID-19 vaccines. In early December, the United Kingdom announced that it would begin administering the Pfizer-BioNTech vaccine; this means beyond the scope of a clinical trial, to large segments of the population. With this and the other vaccines, both in the UK and later in other countries, recipients will be prioritized. Healthcare workers, will get vaccinated first, because of their high risk of becoming infected, whereas priority will also be given to more elderly individuals and others at risk of developing severe COVID-19 disease, should they become infected with SARS-CoV2 (the virus that causes COVID-19). It makes sense for elderly people to be prioritized, since the Pfizer-BioNTech vaccine, as well as the Moderna vaccine, has been shown to be particularly effective at preventing the severe pulmonary complications of SARS-CoV2 that typically lead to admission to the ICU and the need for mechanical ventilation. With these and the other vaccines, as large numbers of doses become available, immunization will expand to increasingly more people. After healthcare workers and people at high risk of developing complications, priority will go to essential workers, such as food service people and also teachers and others vital to school systems. While all of this is happening, there will be testing of the vaccines in pregnant women, but as for the prioritization, the news is both good and bad.

The bad news is that researchers generally avoid including pregnant women in clinical trials of many treatments, including vaccines, due to unknowns related to the embryo or fetus. The good news, however, is that, as data have become available from the trials of the various COVID-19 vaccines, the effectiveness has looked phenomenal, while the side effects have been minimal. In medicine, virtually everything comes down to the balance between the risks versus the benefits of any intervention. Given that COVID-19 is often a life-threatening condition that is caused by an extremely contagious virus, it is becoming ever more clear that the risk of not vaccinating pregnant women will outweigh the risk of including pregnant women in clinical testing. Given the global scale of the COVID-19 crisis and the fairly mild side effect profile of the vaccines in phase 2 testing of non-pregnant people, it is reasonable to predict that, once administration of the vaccine moves from phase 3 testing to widespread administration to healthcare workers and other high risk populations, pregnant women will be offered the opportunity to volunteer for testing. Since all of the vaccines being tested clinically are high-tech, molecular vaccines (meaning that the business end of the vaccine is a piece of genetic material) rather than being a “live vaccine” (a form of the disease-causing agent that has been rendered less viable at causing disease), there is no particular rationale for why the COVID-19 vaccines should be particularly risky in pregnancy settings. Consequently, the risks of volunteering for such studies will be low, as it is for non-pregnant volunteers. Then, once there are safety data particular to pregnant women, the confidence level will be higher and an increasing number of pregnant volunteers will be tested and one or more of the vaccines will then be made available to all or most pregnant women.

David Warmflash
Dr. David Warmflash is a science communicator and physician with a research background in astrobiology and space medicine. He has completed research fellowships at NASA Johnson Space Center, the University of Pennsylvania, and Brandeis University. Since 2002, he has been collaborating with The Planetary Society on experiments helping us to understand the effects of deep space radiation on life forms, and since 2011 has worked nearly full time in medical writing and science journalism. His focus area includes the emergence of new biotechnologies and their impact on biomedicine, public health, and society.

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