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Calling on the brilliant twitter minds on #vaccine #pregnancy #placenta #mrna #immunology #fetalLet's talk SarsCOV2 vaccine and pregnancy 1/
it is acknowledged that pregnant and lactating people were NOT included in vaccine trials.
As such, we are, again, left without information on how to guide us in vaccinations when it comes to counseling these people on risk/benefits of a SarsCov2 vaccine 2/
As such, we are, again, left without information on how to guide us in vaccinations when it comes to counseling these people on risk/benefits of a SarsCov2 vaccine 2/
mRNA vaccine (Pfizer and Moderna) are believed to be safe in the general population (excluding pregnant people)
In simplest terms, genetic code is delivered, spike protein is made, immune system creates antibody. great. 3/
In simplest terms, genetic code is delivered, spike protein is made, immune system creates antibody. great. 3/
Now, pregnant people.
We know that immunizations during pregnancy induce antibody response (thou, surprisingly less data on this then there should be...for another day)
We know that IgG antibodies cross the placenta and provide some protection to the neonate 4/
We know that immunizations during pregnancy induce antibody response (thou, surprisingly less data on this then there should be...for another day)
We know that IgG antibodies cross the placenta and provide some protection to the neonate 4/
BUT, huge 'BUT" here, we have never given mRNA vaccines to pregnant women. We have no data.=, no experience.
While the jury is out (in my mind ) whether pregnant people are at more or less risk for morbidity than age-matched non-pregnant women, they are still at risk 5/
While the jury is out (in my mind ) whether pregnant people are at more or less risk for morbidity than age-matched non-pregnant women, they are still at risk 5/
So, we want to be able to offer vaccination. Let's consider the potential fetal risks. We need to answer some key questions.
First &most important one is: DOES MRNA CROSS THE PLACENTA???
And even if it does not cross in its native state, can it cross in a 'package"? 6/
First &most important one is: DOES MRNA CROSS THE PLACENTA???And even if it does not cross in its native state, can it cross in a 'package"? 6/
and if this is an easy answer that several of us missed, please inform now so the thread can end.
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if not, let's assume mRNA gets to the placenta intact, then
will placental enzymes degrade it?(maybe? perhaps? no?) 7/
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if not, let's assume mRNA gets to the placenta intact, then
will placental enzymes degrade it?(maybe? perhaps? no?) 7/
If mRNA can cross the placenta and is intact, then
how will the fetal immune system respond?
I would offer that it depends on gestational age and immune development
If the fetal immune system responds, what does that mean? 8/
cross the placenta and is intact, then how will the fetal immune system respond?I would offer that it depends on gestational age and immune developmentIf the fetal immune system responds, what does that mean? 8/
If the fetal immune system IS capable of doing similar immunological responses as an adult, then the fetus would create spike protein but can it create antibody?
if it does create the antigenic protein and the fetus DOES mount an immune response is this good or bad? 9/
if it does create the antigenic protein and the fetus DOES mount an immune response is this good or bad? 9/
Our work and work of others has shown that a fetal immune response to inflammation (in the absence of overt bacteria) can lead to fetal brain injury. These model systems may not correlate with an immune response to an antigenic challenge. But, we do not know. 10/
We know that placental passage of maternal IgG (facilitated thru Fc receptors) can lead to higher concentrations of IgG in fetus than mom. So maternal antibody production is good!
I retain a theoretical concern about fetal immunity because we know so little. 11/
I retain a theoretical concern about fetal immunity because we know so little. 11/
Ultimately, the risk/benefit of vaccination of pregnant people will be the 
of the discussion.
The fact remains that until we include pregnant & lactating people in clinical trials, we will be guessing at what is best for them. We owe them more than guessing.
of the discussion.The fact remains that until we include pregnant & lactating people in clinical trials, we will be guessing at what is best for them. We owe them more than guessing.
