COVID Transmissions for 3-7-2022

Vaccination during pregnancy confers protection at birth; COVID-19 during pregnancy confers risk of death

Mar 07, 2022

Greetings from an undisclosed location in my apartment. Welcome to COVID Transmissions.

It has been 812 days since the first documented human case of COVID-19. In 812, the Eastern Roman Empire (Byzantine) recognized Charlemagne as an Emperor—of the Frankish Empire. For a moment, I imagine, it seemed once again like Western and Eastern Europe might both be united under allied Empires. That didn’t exactly work out, owing partly to Frankish inheritance laws carving Charlemagne’s empire into small pieces. For the time, he had a surprising number of children who survived to adulthood.

Speaking of surviving to adulthood, today I am going to walk through some important information about COVID-19, and COVID-19 vaccination, during pregnancy—and how both situations can impact any child that results.

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Now, let’s talk COVID.

Infants can be protected against severe COVID-19 by vaccination during pregnancy

I want to start by sharing with you this study, which establishes that vaccination of a parent during their pregnancy confers protection from COVID-19 to that parent’s eventual child: https://www.cdc.gov/mmwr/volumes/71/wr/mm7107e3.htm

This comes on the heels of another study showing transfer of antibodies from parent to fetus during pregnancy: https://jamanetwork.com/journals/jama/fullarticle/2788986

Infants born from a parent vaccinated during pregnancy were, on average, 61% protected against future hospitalization due to COVID-19 in the first 6 months of life. Interestingly, 80% protection was achieved if the parent was vaccinated late in pregnancy, while vaccinations early in pregnancy conferred only 32% protection. The second study looked at infants born to a parent vaccinated between 20 and 32 weeks into pregnancy, and saw meaningful transfer of antibody to the infant in such parents.

In fact, the authors of that second study compared the vaccinated parents to parents who had recovered from infection with SARS-CoV-2, and were able to demonstrate that in their population, vaccination during pregnancy led to superior levels of antibodies in newborns than being born to a recovered parent did:

Persistence of Antibody in Infants After Maternal COVID-19 Vaccination or Infection — Image shows antibody levels (average level indicated by black line) in parental serum (left), umbilical cord blood (2nd from left), and born infants (3 rightmost entries; data at 2 and 6 months shown) in situations of parental vaccination (dark blue) vs parental recovery from infection (tan). Notably, in the recovered condition (for which there is no data for the second month of infant life, unfortunately), antibody levels are meaningfully lower in serum from recovered parents, in the associated cord blood, and in the infants at 6 months (the difference is less apparent in that last one due to the scale, but it was statistically significant and there are many more infants with remaining antibodies in the vaccinated-parent group).

Both of these studies looked at mRNA vaccines, so we need to acknowledge that other vaccines that do not elicit as much of an antibody response might not have the same performance.

Now I want to take a deeper dive into what’s going on here, and also take the opportunity to talk in general about other examples of vaccination during pregnancy and other strategies that are used to protect infants from vaccine-preventable infectious diseases. This will be a bit of a digression, but there is a payoff here.

In a past segment of my career, I worked on pertussis vaccines. Pertussis is a terrible disease, also known as whooping cough, that can cause a lot of harm to young children, particularly infants. Unfortunately, the bacteria that cause it happen to be present in a very large proportion of adults, and from the moment that a new person is born, they are at risk from the various family who want to see them. Under the current vaccination schedule, the first vaccination for pertussis is performed at the 2-month checkup.

Waiting two months to let your family see a new baby is, shall we say…unpopular, particularly with grandparents.

Two strategies are used to avoid exposing infants to danger, while still allowing them to be introduced to families. The first is known as “cocooning,” and involves all close contacts of the child getting vaccinated. This is kind of an inverse of the “ring vaccination” strategy used in disease outbreaks, where all the contacts of a positive case are vaccinated to contain the outbreak. Cocooning, instead, shields the vulnerable person by surrounding them with vaccinated people.

The other strategy is maternal vaccination, the formal scientific term for when the parent who gives birth to the child is vaccinated in order induce transfer of antibodies to the child. If there is a gender-neutral version of this term, I’m not aware of it.

I have mentioned here before that antibodies can be transferred from pregnant parent to child, but we have not really gone into depth about how that really works. The circulating antibody population from the parent can be passed, through the blood in the fetus’s placenta,1 to the fetus. Antibodies transferred in this way last for around 6 months, which gives the child’s immune system some more time to develop after birth.

Interestingly, this is not a continuous process. While it does appear that antibodies can pass across the placenta, there are optimal and suboptimal times during a pregnancy for them to do so.

For pertussis protection, scientific investigation has established that the best time to get the vaccination during pregnancy is between the 27th and 36th week of the pregnancy, so at the very end of the second trimester or during the 3rd trimester.

Bringing this back to COVID-19, here we see something similar starting to play out in the data. While the second study that I linked provided evidence for the transfer of antibodies from parent to child during pregnancy, I am generally reluctant to make a statement about effectiveness on the basis of antibodies alone, and have been waiting for evidence like the first linked study. The work on antibody levels told us that antibodies pass to infants during pregnancy, if the parent is vaccinated—now we know that protection is also conferred.

I suppose something that is absent from the first study is an analysis of the antibody levels in the protected infants, but perhaps that sort of work will be done a little further down the road. For now we will have to settle for evidence derived from two different populations.

What we’ve also learned here is that there seems to be an ideal time to be vaccinated in order to confer COVID-19 protection, which appears to be later in pregnancy. This is not a huge surprise, since—as I mentioned—we’ve seen that a similar timing with pertussis vaccination has a similar effect as far as antibody transfer and protection.

At this point, it appears that we now have two strategies to protect infants who cannot be vaccinated against COVID-19, and both are similar to what is used in pertussis. We can attempt something like cocooning, by vaccinating all of an infant’s close contacts and using masking and other techniques to reduce the chances of infection. We can also use vaccination during pregnancy to confer at least 6 months of protection.

Now we just need a vaccine to cover the period between 6 months and 5 years of life. I hope it comes soon.

Placental disruption by COVID-19 during pregnancy

As if there were not already many reasons to be concerned about getting COVID-19 during pregnancy, we have a new one: COVID-19 can damage the placenta. This study includes 68 cases of placental damage following SARS-CoV-2 infection that led to stillbirth or neonatal death (that’s death within 28 days of live birth): https://meridian.allenpress.com/aplm/article/doi/10.5858/arpa.2022-0029-SA/477699/Placental-Tissue-Destruction-and-Insufficiency

What appears to be happening here is that due to damage to the placental tissue, the fetus is unable to get enough oxygen to live. Everything that the fetus gets in terms of nourishment goes through the placenta, but oxygen supply is one that can do the most damage the most quickly.

As I said, there are a lot of reasons to get vaccinated for COVID-19 before or during a pregnancy, but this is another very serious reason to add to the list.

Part of science is identifying and correcting errors. If you find a mistake, please tell me about it.

Though I can’t correct the emailed version after it has been sent, I do update the online post of the newsletter every time a mistake is brought to my attention.

No corrections since last issue.

What am I doing to cope with the pandemic? This:

Considering a change in newsletter schedule

The COVID-19 situation has cooled off a bit in most places that readers of this newsletter hail from. With that in mind, I am wondering if there would be big objections to my moving to a twice-weekly schedule for this newsletter temporarily. While I am sure I could find things to continue to write about three times weekly, the stories are thinner on the ground lately and I wonder if your inboxes—and my typing fingers—couldn’t use a bit of a break.

3x weekly frequency would resume if and when there is a resurgence in COVID-19.

Let me know in the comments! Don’t be shy.

Reader Hope writes:

It’s frustrating that after decades watching for the next ‘Flu of 1918’, all the US surveillance for it was shut down less than 3 years before it struck. To your knowledge, is that infrastructure rebuilt now, or is the current crisis narrowing focus to the pandemic we already have?

A topic close to my heart. My reply:

Good question. I am not sure how much of the effort has been implemented, given the focus on ending the current pandemic, but I do know the current White House administration has at least produced a plan for future pandemic preparedness: https://www.whitehouse.gov/wp-content/uploads/2021/09/American-Pandemic-Preparedness-Transforming-Our-Capabilities-Final-For-Web.pdf
I am also aware that the CARES and HEROES acts provided substantial funding an expansion of anti-pandemic infrastructure, that could be used both against the current disaster as well as future pandemics.
In my opinion, this disaster that has cost the world many trillions of dollars might have been avoided if each country affected had just spent some billions more annually on surveillance and preparedness.
The problem is, you don't get to take credit for the pandemics you prevent. As we see on the personal scale with anti-vaccination attitudes, people do not appreciate the benefits of being protected from health disasters. It is somewhat understandable, really. When SARS-CoV-1 didn't become a pandemic, did the world react with global celebration in realization that it could have been so much worse? No. We went on with our lives, because most people just couldn't imagine that there might have been a SARS-CoV-2 eventually that would cause global disruption. I don't know what the solution to that particular problem is, but it stands in the way of politicians feeling incentivized to engage in preventative planning rather than reactive disaster management.

You might have some questions or comments! Join the conversation, and what you say will impact what I talk about in the next issue. You can also email me if you have a comment that you don’t want to share with the whole group, or if you are unable to comment due to a paywall.

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