First Exposure

COVID-19 mRNA Vaccine in Pregnancy and Lactation

This health topic is an expert opinion about the mRNA COVID-19 vaccine during pregnancy and lactation.

* The information provided is the expert opinion of the First Exposure Medical Advisors. It is for informational purposes only and does not replace medical care and advice from a healthcare provider. Please contact your healthcare provider if you have any concerns or to discuss any questions that you believe may be relevant to you or your baby. In case of emergency, please go to the emergency room or call 911.

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Clinical scenario:

I am currently pregnant. I received 2 doses of an mRNA COVID-19 vaccine prior to pregnancy. Should I receive another mRNA COVID-19 vaccine during my pregnancy? Is it safe to get an mRNA COVID-19 vaccine while pregnant and/or while nursing?

Q. What is COVID-19 infection?

A. Coronavirus disease 2019 (COVID-19) is an infection caused by the SARS-CoV-2 virus (first recognized in December 2019). SARS-CoV-2 virus continues to change, resulting in variants that are different from the original SARS-CoV-2 virus. SARS-CoV-2 virus is spread through respiratory droplets and aerosols (smaller droplets that can linger in the air, especially in indoor spaces), which are created when an infected person breathes, coughs, sneezes, or talks. The virus can also be spread by touching something that has the virus on it, then touching your mouth, nose or eyes without washing or sanitizing your hands.

Common symptoms of COVID-19 include sore throat, runny nose, sneezing, new or worsening cough, difficulty breathing, fever, chills, fatigue or weakness, muscle/body aches, new loss of smell or taste, headache, or abdominal pain and diarrhea. For more information on COVID-19, please refer to Public Health Agency of Canada

Please reach out to a health care provider when feeling unwell, especially if your symptoms get worse, do not resolve in a few days, you develop a fever, your phlegm turns yellow/green or you develop a persistent cough. 

Q. Why is COVID-19 infection a concern in pregnancy?

A. Pregnant individuals are at higher risk of severe illness from COVID-19.  Complications may include increased risk of hospitalization and admission to the intensive care unit (ICU) compared to those who are not pregnant and of similar age. Being sick from COVID-19 increases the chances of adverse effects on the pregnancy and developing baby, such as preterm birth (delivery before 37 weeks of pregnancy), low birth weight and admission to the neonatal intensive care unit (NICU). Studies have shown that pregnant individuals who are vaccinated against COVID-19 are less likely to have severe illness or pregnancy complications compared to those who are not vaccinated.

Q. What is a COVID-19 mRNA vaccine and how does it work?

A. The COVID-19 mRNA vaccine is given by an injection, usually in the upper arm. mRNA is a molecule that contains “instructions” for making the SARS-CoV-2 spike protein (a protein found on the surface of the SARS-CoV-2 virus that helps it to bind to cells). After the spike protein is made, the mRNA is broken down and our body gets rid of it. Our immune system recognizes the spike protein as not belonging in our bodies and builds antibodies (proteins from the immune system) that help fight against infection.

Q. Does the COVID-19 mRNA vaccine change our DNA?

A. mRNA does not enter the nucleus inside of our cells where DNA is found. Our DNA cannot be changed by an mRNA vaccine.

Q. Are there side-effects to the COVID-19 mRNA vaccine?

A. Side effects include sore arm, fever, or muscle aches which are short lived/self-limiting. Side effects, such as fever, can be treated with acetaminophen during pregnancy.  The vaccine does not contain live virus and thus, there is no risk of the vaccine causing COVID-19 infection.

Q. What are the recommendations for pregnant individuals in Canada with respect to an mRNA vaccine?

A. Data from studies including thousands of pregnancies support the safety and effectiveness of the COVID-19 vaccine in pregnancy. The National Advisory Council on Immunization (NACI) in Canada recommends that pregnant individuals (at any stage of pregnancy) receive the primary series of the COVID-19 vaccine. 

For the 2023-2024 autumn-winter season NACI recommended a dose of XBB.1.5-containing formulation for pregnant individuals who were previously vaccinated against COVID-19, if it has been at least 6 months from the previous COVID-19 vaccine dose or known SARS-CoV-2 infection. Please reach out to your healthcare provider for the most updated NACI recommendations.

Q. Will receiving the COVID-19 vaccine while trying to conceive affect the chances of getting pregnant?

A. Studies have found no link between receiving an mRNA COVID-19 vaccine and current or future fertility, including male fertility.

Q. Does receiving an mRNA COVID-19 vaccine in pregnancy increase the chance of miscarriage?

A. Studies have found that receiving an mRNA COVID-19 vaccine during pregnancy does not increase the risk of miscarriage.

Q. Does receiving an mRNA COVID-19 vaccine in pregnancy increase the chance of a birth defect?

A. The baseline risk of major birth defects in Canada is 3-5%. This means that 3-5 out of 100 babies born in the general population in Canada will be born with a major birth defect. Studies have found that receiving an mRNA COVID-19 vaccine in pregnancy does not increase the risk of birth defects above the baseline risk.

Q. Does receiving an mRNA COVID-19 vaccine in pregnancy increase the risk of any other harmful pregnancy outcomes?

A. Studies have not identified an association between receiving the COVID-19 vaccine during pregnancy and an increased risk of other adverse pregnancy outcomes such as stillbirth (loss of a baby before or during delivery), preterm birth, or low birth weight. In fact, some studies have shown lower rates of stillbirth and preterm delivery in mothers vaccinated with the COVID-19 vaccine during pregnancy compared to those who did not get the vaccine.

Q. Does receiving an mRNA COVID-19 vaccine during pregnancy impact the baby’s health at birth?

A. The mRNA vaccine itself does not cross the placenta; only protective antibodies produced during pregnancy in response to the vaccine cross the placenta. Receiving an mRNA COVID-19 vaccine at any stage of pregnancy has not been found to negatively affect the baby’s health at birth. In fact, the newborn may be protected against COVID-19 infection during the first few months of life. This is especially important as infants cannot be vaccinated until 6 months of age.

Q. Does receiving an mRNA COVID-19 vaccine in pregnancy affect future health or behavior of the child later in life

A. Studies of childhood outcomes following COVID-19 vaccination in pregnancy are underway. Receiving the COVID-19 vaccine during pregnancy is not expected to affect the future health or behaviour of the child. Limited data indicate that an mRNA COVID-19 vaccine given in pregnancy is not associated with infant hospitalizations or death. A study reported no increased risk of developmental delay at 12 and 18 months, in the children of those who had been vaccinated in pregnancy, compared to those who had not.

Q. Can you receive an mRNA COVID-19 vaccine while nursing?

A. The mRNA COVID-19 vaccine is recommended while nursing. Hundreds of nursing individuals and their infants have been studied and there are no known or suggested serious safety concerns. Furthermore, receiving the COVID-19 vaccine postpartum will help protect the baby and those caring for the baby. Studies have found antibodies in breastmilk 6 weeks after maternal vaccination with an mRNA vaccine, however the actual protection against COVID-19 illness from nursing is unknown. There have been reports of temporary changes in breastmilk supply (both decrease and increase) after receiving a COVID-19 vaccine. Milk supply usually returns to baseline within a few days.

Q. In addition to the vaccine, are there ways to prevent getting COVID-19 infection?

A. The best ways for preventing COVID-19 infection are handwashing, avoiding others who are sick, wearing a well-fitted respirator or mask when indicated, and improving indoor ventilation when possible. Please consult your local public health for recommendations on infection prevention.

Q. Advice for specific populations?

A. Despite pregnant individuals being prioritized for the COVID-19 vaccine during the pandemic, uptake has been lower compared to the general population. Low vaccination rates and negative effects of COVID-19 are seen more often in those who are pregnant and racialized, younger, have a lower household income or live in remote areas. Access to healthcare and treatment can vary widely among different populations, leading to differences and gaps in the management of COVID-19 infection in pregnancy. Addressing equity issues requires efforts at multiple levels to ensure all pregnant individuals have access to appropriate care and treatment.

Key References

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First Exposure does not offer health care treatment. If you have an urgent question about your pregnancy or your baby’s health, you should contact your health care provider directly. If you don’t have a health care provider and you live in Ontario, you have a variety of health care options. In the case of an emergency, visit a hospital emergency room or call 911.