mRNA Vaccines
Pregnancy and novel mRNA vaccines.

Pregnancy and novel mRNA vaccines.

So we have had a few readers asking whether pregnant and lactating women should receive either of the novel mRNA vaccines (Moderna or Pfizer).

We cannot definitively state that either of these COVID vaccines are safe for use in pregnancy. We say this, not because there is any indication that either of these vaccines may be harmful during pregnancy or lactation. We do this in an abundance of caution (as any other legitimate healthcare provider and scientists would do), as there are no studies in existence which evaluate these questions and outcomes. At this time, since there are no clinical trials where pregnant women were studied for complications (miscarriages, pre-eclampsia/eclampsia, etcetera), we are unable to compare the incidence rates of complications post-vaccination (so far, there have been no reported adverse pregnancy outcomes) with the incidence rates of the general public. Because of the lack of evidence, it is impossible to determine whether any negative effects that may happen/occur are due to the vaccine, or whether they occur outside of normally occurring rates.

So, now that we have that out of the way, let’s talk about the potential for pregnancy/lactation risks, and how these risks are insignificant and unlikely to cause adverse events during pregnancy and lactation.

Most vaccines available on the market today are given during childhood, and not repeated during a pregnancy or lactation. There are currently three vaccines which are commonly given during adulthood, during times of higher risk and potential/confirmed pregnancy. These three vaccines are the Measles/Mumps/Rubella vaccine, the Diphtheria/Tetanus/Pertussis vaccine, and the influenza vaccine.

The reason why these vaccines are recommended in the time surrounding pregnancy and lactation is due to the increased risk of the mother and child of vaccine preventable diseases. Let’s walk through each of the diseases that we are using vaccines to prevent during pregnancy/lactation and why this is so important.

Rubella (or German Measles as it is sometimes called) is a vaccine preventable disease which causes birth defects (blindness, deafness, development disabilities, and autism to name a few), especially if the mother is exposed to Rubella during the first 2 trimesters. In the 1960s before the rubella vaccine, over 10,000 babies were born deaf and blind, over 11,000 second/third trimester babies where miscarried, and there were an unknown number of miscarriages due to mothers being exposed to Rubella during early pregnancy (in the 1960s, the home pregnancy test didn’t exist, so pregnancies were confirmed much later than they are today, which makes it difficult to estimate the number of early pregnancy miscarriages).

The devastation of Rubella during pregnancy was so common, it has its own name: Congenital Rubella Syndrome (CRS). Congenital Rubella syndrome causes the following problems in the infant:

• heart defects,

• glaucoma and cataracts,

• Intellectual, learning, and developmental disabilities,

• Deafness,

• Diabetes,

• Enlarged liver and/or spleen,

• Low birth weight,

• Growth retardation

While Rubella is uncommon in the United States, around 1,000 babies are still born here with Congenital Rubella Syndrome, and all women of childbearing age should receive the MMR prior to getting pregnant to boost these immunities or after delivery, to provide immunities to the infant until they’re old enough to get vaccinated.

Since the MMR is a live virus, it is not recommended that pregnant women receive the vaccine, as the baby’s immune system will be unable to fight off even an attenuated virus, and could cause the baby to develop CRS from the vaccine. Once the infant is born, there is a separation between the mother and child, which doesn’t allow the child to be directly infected by an attenuated vaccine, yet the mother will produce antibodies to Rubella (and Measles/Mumps) and pass them onto the child.

The second vaccine that is recommended during pregnancy is the Diphtheria/Pertussis/Tetanus vaccine (as a TDaP/DTaP). Women are advised to received this vaccine for the prevention of Pertussis, a bacteria which can cause severe cough in adults and can be deadly, especially in infants (the characteristics cough in a infant gives the illness its common name, Whooping Cough).

Pertussis (Whooping Cough) typically presents as a severe cough which expels most of the air in the child’s lungs, followed by a whooping sound as the child gasps to try and breath. Those of us who have been in healthcare for decades can hear the cough in our sleep. Often the cough is so severe that is interferes with the child’s ability to eat and control secretions, placing the child at risk for dehydration, secondary infections, and worsening illness.

Pertussis is a vaccine preventable illness, meaning that vaccinations decrease the risk and spread of pertussis significantly. Due to the nature of the bacteria and vaccine, pertussis immunity wanes with time, just like the immunity for tetanus (both last between 15-30 years). This is why it is especially important and why many states/hospitals recommend both the mother and father of all new babies be vaccinated for pertussis.

The Pertussis vaccine is a protein derivative, and doesn’t have the actual bacteria present in the vaccine, hence there isn’t a risk of an unborn child getting diphtheria, pertussis, or tetanus from the mother getting the vaccine during pregnancy. Due to the low risk for vaccinations during pregnancy, most OB/Gyn physicians recommend the mother and father receive the vaccine prior to delivery.

The third common immunization in adults is the influenza vaccine. Influenza is a common complication of pregnancy, resulting in an increased risk for maternal death, increased risk for premature delivery, and for the death of the baby. Influenza (and the concomitant immune response is hypothesized to contribute to the risk of neural tube defects) effects pregnant women differently, as pregnancy itself alters the immune, respiratory and cardiac systems. Influenza vaccinations during pregnancy is associated with a 40% reduction in hospitalizations for influenza in pregnant women. This is a significant reduction in the severity of illness, can help to reduce neural tube defect rates, and can reduce premature deliveries.

Since the influenza vaccine (all but the nasal vaccine) are inactivated (dead) viruses, the vaccine itself is unable to cause influenza in the pregnant woman as well as the unborn child. Since there is little risk of complications from the influenza vaccine and a sizable decrease in hospitalizations and the severity of illness from influenza, the influenza vaccine is recommended in pregnancy.

So let’s take a look at the novel mRNA vaccines for COVID-19. When we look at the three vaccines commonly given to adults and during pregnancy, both of the inactive/dead vaccines are recommended during pregnancy as the risk of illness/complications from the vaccine are minimal, but the risk of illness is fairly significant. The MMR vaccine is not recommended during pregnancy, as it contains a live virus, and is recommended either prior to becoming pregnant or shortly after the delivery of the baby (many doctors what it done prior to discharge from the hospital).

The mRNA vaccines for COVID-19 do not have an active viral component, so it is impossible for either the mother or unborn child to become ill with COVID-19. While there is some risk with any vaccination (potential for anaphylactoid reactions, rash, etcetera), the risk for getting sick with COVID is high for pregnant women being exposed to SARS-CoV-2.

So, this is why the ACIP and the CDC, even though there isn’t an analysis of those who have received the vaccine during pregnancy, have made statements that pregnancy is not a reason to not get the vaccine. The calculated risk with the vaccine is minimal compared to COVID-19.

Based on the data we have on COVID-19 and Influenza, pregnant women are at an increased risk for complications from COVID-19 (both immediate and long term), hence this increased risk of complications and the minimal risk of injury from vaccines, most healthcare providers will likely advise their patients to get vaccinated for COVID-19 during pregnancy, even though we do not have studies confirming the safety of the vaccine during pregnancy.

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