COVID vaccine effective in pregnant women

Real-world data shows the vaccine's effectiveness
20 April 2021

Interview with 

Andrea Edlow, Massachusetts General Hospital, Harvard Medical School


Uncertainty about the effects that many medications can have on the unborn child leave a large number of pregnant women with untreated conditions.


And with another encouraging step forward, the UK’s Joint Committee on Vaccination and Immunisation, the JCVI, has now advised that pregnant women should be offered the COVID-19 vaccine at the same time as the rest of the population, based on their age and clinical risk group. This is a change from the previous guidance that pregnant women should only be vaccinated if their risk from COVID-19 was judged to be high. This initial stance was adopted not because there’s any evidence of danger, but because it’s standard practice not to test new drugs on pregnant women, so there was initially no data on whether the vaccine is safe or effective during pregnancy. Now real-world data from the US is giving reassuring results. Phil Sansom heard about one study, published in the American Journal of Obstetrics and Gynaecology, from Harvard’s Andrea Edlow who’s been measuring antibody levels in 131 vaccinated pregnant women...

Andrea - The levels of those antibodies were equally high in pregnant and lactating women as they were in women of reproductive age who were not pregnant.

Phil - I mean, fantastic! Sounds like good news!

Andrea - It was great news for pregnant and lactating women everywhere.

Phil - Was that not what you were expecting?

Andrea - It's a reasonable question to investigate, because we know that pregnancy is a situation where women are relatively immune tolerant. And that's partly in order to tolerate the developing foetus, which is half-not-the-woman herself.

Phil - Okay. So with these 130 participants, can you be reasonably sure of saying, "yes, these mRNA vaccines work just as well for these people?"

Andrea - Yes. I think we can be reasonably sure at looking at what's called the efficacy of the vaccine, or how well the vaccine functions to give people antibodies.

Phil - What about for the baby? What are the implications?

Andrea - We looked at the women in our study who delivered during the study period, and that was only 10 of the pregnant women. And we found that antibodies were present in the umbilical cord blood of all ten babies - and in the mother's breastmilk.

Phil - So does that mean the babies were actually coronavirus resistant?

Andrea - That is something that our study couldn't specifically look at, because we didn't - of course - go on to try to expose the babies to coronavirus and see if they were resistant to it. But yes, we assume that the presence of antibodies in the umbilical cord will give babies some degree of protection. But how much is needed to give more complete protection, and how long that protection will last in babies, is something that isn't yet known, and our study couldn't answer unfortunately,

Phil - There's obviously a million concerns going around about the vaccine. And one other one that I've actually heard from some people is, they say, "is at a risk if I'm trying to get pregnant?"

Andrea - That's a very good question. And that's a common question that we get a lot as obstetricians. There was some sort of, what - for lack of a better word - I could just honestly call junk science, that was perpetuated early on in the evolution of the vaccines; where people were saying that the mRNA sequence in the vaccine, so the code that the vaccines have that tells your immune system to make these proteins, had some similarity to the code that might be in the placenta. That has been disproven. There actually is extremely little overlap in the mRNA sequence, or code, that's in the virus, with any mRNA that's in the placenta. So that basically was just completely false.

Phil - Now that you've done this study, would you feel confident saying this vaccine is safe for pregnant people, or safe for people who've just given birth, or what?

Andrea - Our study did not specifically look at safety. Our study was designed to look at efficacy, which is: how well does it work to give you antibodies? There are studies that look at safety that are ongoing; Pfizer's doing a trial with over 4,000 pregnant women. But you really need a very large segment of the population to see a safety signal. So our study doesn't look at safety, and the data that do look at safety are still evolving,

Phil - Right, so if I were pregnant, and I were getting offered an mRNA vaccine, what would you tell me?

Andrea - I would tell you that you, together with your trusted care provider - whether that's your obstetrician, a midwife - should look at your risk of getting COVID, your own medical conditions; and then to think about the known risks of having COVID-19 in pregnancy. We know that women who do get COVID-19 in pregnancy are more likely to need a ventilator, more likely to need a heart-lung bypass machine, and unfortunately more likely to die, than women who are the same age who are not pregnant. So weighing all those risks, your own personal risks as well as the general risk of pregnancy, against the small risk of the unknown, where pregnant and lactating women were excluded from the original vaccine trials. So unfortunately we don't have the human safety data in pregnancy that we have in animals. But the animal safety data that the mRNA vaccines have doesn't show concerns. And I think this just highlights why women never should have been left out of these trials in the first place.


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