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Confirmed: COVID-19 Vaccination During Pregnancy Protects the Newborn

A recent study published in the prestigious Journal of the American Medical Association (JAMA) proves what we have all suspected, and have been discussing here on The Pulse, since COVID-19 vaccines became available about a year and a half ago. Getting vaccinated against SARS-CoV2 (the virus that causes COVID-19) while you are pregnant protects your baby against the virus. It does this by providing passive immunity in the form of maternal antibodies that cross within the placenta from the maternal blood to the fetal blood, resulting in protection that lasts for the first four months of life after delivery. This works the same way as the passive immunity afforded by other vaccines given during pregnancy, such as the pertussis vaccine. Involving more than 21,000 pregnancies, the study was conducted in Norway and grouped participating women based on whether or not they were vaccinated during pregnancy. Accounting for various factors, such as maternal age, the number of previous births of each woman, education, and the mother’s country of birth, the JAMA study revealed a clear protective effect of maternal SARS-CoV2 vaccination against a newborn’s risk of testing positive for the virus within four months of birth.

I advise you to weigh the results of this Norwegian study published in JAMA against the plethora of alarmist claims made and spread by anti-vax cultists that we have been confronting for the past year and a half, baseless claims that antivaxxers were making, and continue to make, that maternal vaccination is harmful to the perinate (the fetus/newborn). One such claim, which we debunked here on The Pulse about a year ago was that COVID-19 vaccines would cause infertility and by the same mechanism cause abruptio placentae, detachment of the placenta from the wall of the uterus. The claim, a complete myth, derived from speculation about some similarity between a portion of the spike protein (the viral protein that COVID-19 vaccines teach the immune system to use for target practice) and a protein vital to the fusion of male and female gametes (sex cells) and to holding the placenta to the uterus. The claim was that learning to produce an immune response against the spike protein, the immune system would interfere with fertilization that starts pregnancy and interfere with the integrity of the connection between the placenta and the uterus. But the similarity actually involves, only a short region of the spike protein and the reproductive proteins and the claims of infertility and abruptio placentae are not supported by a shred of evidence. In our discussions, we also confronted a distorted idea promoted by COVID-19 vaccine critic, Dr. Robert Malone, on the Joe Rogan Experience. This idea was that minor changes that women have experienced in their menstrual cycles for a couple of cycles following COVID-19 vaccination constituted evidence that that the vaccines messed around dramatically with their reproductive systems. That idea too is complete nonsense and we explained it in this post where we discussed various US-government-funded studies looking precisely for such problems and finding COVID-19 vaccination during pregnancy to be completely safe.

Given the recent Norwegian study published in JAMA, this is a nice opportunity to review concepts involving immunity and the placenta. Of the various functions of the placenta, immunity is just one of them, but it is a kind of immunity organ, for a good reason. The placenta contains both maternal blood and fetal blood, blood that is never supposed to mix, although it does mix sometimes where there are problems, which can lead to consequences related to conflicting blood types between the mother and fetus. When maternal and fetal blood remain separate however, each flowing through its own set of placental blood vessels, maternal antibodies are nevertheless able to travel from the mother’s blood into the fetal blood. Now, there are different types of antibodies, different flavors of immunoglobulins, of which really only one flavor crosses the placenta from maternal to fetal blood. It’s called immunoglobulin G (IgG). This is one of the two main flavors of antibody that begins circulating in the blood when you are  immunized. The other one is called IgM and it does not cross the placenta, because it is secreted as units of five antibodies attached together, so it is too big to cross. IgM is the first type of antibody that your immune system begins making against the SARS-CoV2 spike protein when you are vaccinated, but over time you make an increasing amount of IgG targeting the same protein. This is especially true following your second vaccine dose and also after your booster shot, if you receive one. Since it’s the IgG antibody that gets through the placenta and protects the fetus, simply receiving your first COVID-19 vaccine dose 2-4 weeks before delivering will NOT provide much protection to the newborn, since you’ll be making mostly IgM, which won’t reach the fetus. On the other hand, completing the two shots of the primary series of COVID-19 vaccination by the middle of pregnancy certainly should provide the fetus with some protective IgG. The take-home message, therefore, is that you should not delay vaccination. The best case scenario is to be vaccinated prior to pregnancy, so that you’ll be starting pregnancy already with a good level of immunity. Antibodies are not the entire immunity armament, but they are what pass to the fetus to protect it, so this means that getting your third shot —your booster— should also be helpful during pregnancy. On the other hand, if you are already pregnant and still not vaccinated, the message from the JAMA study is that you should not delay. You should get vaccinated immediately, not just for your own health, but for that of your baby as well.

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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