First Exposure

Measles Infection and the MMR Vaccine in Pregnancy and Lactation

Authored by Dr. Tali Bogler and reviewed by First Exposure Medical Review Team.

Dr. Tali Bogler, MD, CCFP, MScCH, is a Medical Advisor at First Exposure, a Family physician, and Chair of Family Medicine Obstetrics at St. Michael’s Hospital, an assistant Professor, Department of Family and Community Medicine and Investigator at Li Ka Shing Knowledge Institute.

This health topic is an expert opinion about measles infection and the MMR 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 

 If you do not have a healthcare provider please go to: Finding a Healthcare Provider 

 

Clinical scenario:

I am trying to get pregnant and worried about measles. How do I know if I’m immune to measles and what if I am exposed to measles during my pregnancy?

 
Q. What is Measles?
A. Measles is a highly contagious infection caused by the measles virus. The symptoms usually include fever, cough, runny nose, red eyes followed by a distinctive rash. For more information on signs and symptoms of measles, please refer to: WHO Fact Sheet Measles

Measles is spread through contact with infected nasal or throat secretions (e.g., when an infected person coughs or sneezes) or breathing the same air as someone with measles. The virus can remain in the air or on infected surfaces for up to two hours. The airborne nature of the virus makes it highly contagious.

Any person who has no immunity to the virus can become infected. Please see below for information on how to know if you are immune to measles

Measles infection can lead to serious complications such as lung infection (pneumonia), inflammation of the brain (encephalitis), and even death. Infections can be particularly severe in vulnerable populations such as unimmunized infants, young children, pregnant individuals, and those who have weakened immune systems.

Vaccination is the most effective way to prevent measles.

Q. Why are there outbreaks if measles was eliminated in Canada?

A. Endemic measles has been eliminated in Canada (i.e., no ongoing circulation) since 1998 due to successful vaccination programs. However, cases or outbreaks can still occur as current immunization rates in Canada have fallen below the 95% needed to provide population immunity.

Measles is still circulating in some other countries. When a person who is unvaccinated or non-immune contracts measles in a country where measles is circulating, they may be infectious upon entering Canada. Since measles is highly contagious, spread can occur when an unvaccinated person comes into contact with a person who is actively infectious and contagious.

Q. How do I know whether I am immune to measles?
A. If you had a confirmed measles infection in the past or have documentation of receiving the recommended immunization(s) against measles, you are considered immune. If you do not have a copy of your immunization records, discuss with your healthcare provider whether you should do a blood test to measure measles-specific antibodies to determine your immune status or receive an additional measles-mumps-rubella (MMR) vaccine, as it is safe to receive additional doses of an MMR vaccine in those who are already immune. Please see below about receiving an MMR vaccine if you are trying to conceive or are pregnant.
 
Health care providers should use pre-conception counseling as an opportunity to review immunization status.
Q. Is measles infection a concern in pregnancy? 

A. Pregnant women and pregnant individuals who are not immune to measles (please see previous question for information on how to know if you are immune to measles) are at increased risk of more severe complications for themselves such as hospitalization, pneumonia, hepatitis and encephalitis.

There is also an increased risk of adverse pregnancy outcomes such as miscarriage, stillbirth (loss of a baby before or during delivery), preterm birth (delivery before 37 weeks of pregnancy), and low birth weight. Measles infection in pregnancy does not appear to increase the risk of birth defects.

When measles infection occurs during pregnancy within 10 days of delivery, there is a risk for congenital infection. It is considered congenital measles when the newborn has measles within the first 10 days of life. Congenital infection is linked to an increased risk of infant death and a rare neurological disorder (disorder of the brain) called subacute sclerosing panencephalitis.

Q. What is the measles vaccine?

A.  In Canada, the measles vaccine is a combined vaccine available as MMR or measles-mumps-rubella-varicella (MMRV). It is a ‘live-attenuated’ vaccine, meaning it contains a weakened form of the virus to stimulate the immune system to produce antibodies without causing the disease itself.

In Canada, children receive two doses of a measles-containing vaccine as part of routine immunization. The efficacy of a single dose of a measles-containing vaccine given at 1 year of age is estimated to be around 85-95%. With a second dose, efficacy approaches 100%. To learn more about the routine vaccination schedule for measles in your province or territory, please refer to the Public Health Agency of Canada Vaccination Schedule

Q. What are the recommendations for pregnant women and pregnant individuals in Canada with respect to a measles-containing vaccine?

A.  Live vaccines are generally not recommended during pregnancy due to the theoretical risk of infection with a live component of the vaccine. Because MMR is a live attenuated vaccine, it is also not generally recommended in pregnancy. There may be special situations in which public health officials suggest considering vaccination in pregnancy. Consult with your physicians or local public health officials for more information.

Q. What if I am trying to get pregnant, can I receive an MMR vaccine?

A. Following immunization with MMR vaccine, it is advised to wait for at least four weeks to get pregnant. When you are planning a pregnancy, it is suggested to review your immunity to measles, and other viruses with your healthcare provider, so that you can receive the vaccinations before pregnancy.
 

Q. I just found out that I am 6 weeks pregnant and received an MMR vaccine last week.

Will it…

Q. Increase the chance of miscarriage?  

A.  There was no increased risk of miscarriage in studies following women who received the MMR vaccine either during pregnancy or in the few weeks before pregnancy.

Q. 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 did not find that receiving an MMR vaccine in pregnancy increases the risk of birth defects above the baseline risk.

Q. Increase the risk of any other harmful pregnancy outcomes?  

A. Studies have not found increased risks of any other harmful pregnancy outcomes, such as preterm birth (delivery before 37 weeks of pregnancy), stillbirth and low birth weight.
 

Q. Can you receive an MMR vaccine while breastfeeding?  

A. If you are not immune to measles, it is recommended to receive the MMR vaccine postpartum, including if breastfeeding. 

Q. I am 12 weeks pregnant and learned that I have been exposed to measles. I am not immune. Is there anything I can do?

A. Pregnant women and pregnant individuals who are not immune and have had exposure to measles may be offered immunoglobulins. Immunoglobulins are proteins produced by blood cells to fight infections and provide protection from similar infections in the future. When a non- immune person is exposed to an infection that may cause serious adverse outcomes, such as measles infection in pregnancy, they can be given immunoglobulins to help prevent infection. The immunoglobulin should be given as soon as possible, because it is shown to be effective when given within 6 days after exposure. It is important to note that measles infection may still occur in some individuals after receiving immunoglobulins. Exposed individuals should monitor for symptoms. Should symptoms develop, they should stay at home, and call their health care provider or local public health unit as soon as possible. When immunoglobulins are given they provide short-term protection. If a non-immune pregnant woman has another exposure to measles weeks later, another dose of immunoglobulins may be needed. 

Q. What can primary care and maternity care providers do to limit the spread of measles and help protect their patients?

A. Health care providers should use pre-conception and pregnancy care as an opportunity to review immunization status. This will allow for more opportunities to administer live vaccines prior to conceiving or postpartum and further help protect our patients, their families, and communities at large.

Key References:

Badilla X, Morice A, Avila-Aguero ML, Saenz E, Cerda I, Reef S, Castillo-Solórzano C. Fetal risk associated with rubella vaccination during pregnancy. Pediatr Infect Dis J. 2007 Sep;26(9):830-5. [PMID: 17721380].

da Silva e Sá GR, Camacho LA, Stavola MS, Lemos XR, Basílio de Oliveira CA, Siqueira MM. Pregnancy outcomes following rubella vaccination: a prospective study in the state of Rio de Janeiro, Brazil, 2001-2002. J Infect Dis. 2011 Sep 1;204 Suppl 2:S722-8. [PMID: 21954273].

Laris-González A, Bernal-Serrano D, Jarde A, Kampmann B. Safety of Administering Live Vaccines During Pregnancy: A Systematic Review and Meta-Analysis of Pregnancy Outcomes. Vaccines (Basel). 2020 Mar 11;8(1):124. [PMID: 32168941]. [PMC7157743].

Public Health Agency of Canada. Adult National Immunization Coverage Survey (aNICS): 2023 results. [Internet]. Ottawa, ON: Public Health Agency of Canada; 2024 [updated Jan 17, 2024; cited 2024 May 3]. Available from: https://www.canada.ca/en/public-health/services/immunization-vaccines/vaccination-coverage/adult-national-immunization-coverage-survey-2023-results.html

Public Health Agency of Canada. Highlights from the 2021 childhood National Immunization Coverage Survey (cNICS). [Internet]. Ottawa, ON: Public Health Agency of Canada; 2021 [updated May 14, 2024; cited 2024 May 22]. Available from: https://www.canada.ca/en/public-health/services/immunization-vaccines/vaccination-coverage/2021-highlights-childhood-national-immunization-coverage-survey.html#what.

Public Health Agency of Canada. Measles vaccines: Canadian Immunization Guide. [Internet]. Ottawa, ON: Public Health Agency of Canada; 2015 [updated September 8, 2023; cited 2024 April 8]. Available from: https://www.canada.ca/en/public-health/services/publications/healthy-living/canadian-immunization-guide-part-4-active-vaccines/page-12-measles-vaccine.html.

Public Health Agency of Canada. Measles: For Health Care Professionals. [Internet]. Ottawa, ON: Public Health Agency of Canada; 2024 [updated May 6, 2024; cited 2024 April 26]. Available from: https://www.canada.ca/en/public-health/services/diseases/measles/health-professionals-measles.html

Public Health Ontario. Measles. [Internet]. Toronto, ON: Ontario Agency for Health Protection and Promotion; April 2015 [updated 2024 Apr; cited 2024 May 3]. Available from: https://www.publichealthontario.ca/en/Health-Topics/Immunization/Vaccine-Preventable-Diseases/Measles

Rasmussen SA, Jamieson DJ. What Obstetric Health Care Providers Need to Know About Measles and Pregnancy. Obstet Gynecol. 2015 Jul;126(1):163-70. [PMID: 25899422] [PMC4552307].

Tunis MC, Salvadori MI, Dubey V, Baclic O; National Advisory Committee on Immunization (NACI)*. Updated NACI recommendations for measles post-exposure prophylaxis. Can Commun Dis Rep. 2018 Sep 6;44(9):226-230. [PMID: 31015814] [PMC6449113].

Wong C. Measles outbreaks cause alarm: what the data say. Nature. 2024 Jan 31. Epub ahead of print. PMID: 38297056.

World Health Organization. Measles. [Internet]. Geneva, CH: World Health Organization; 2024 [updated April 16, 2024; cited 2024 April 19]. Available from: https://www.who.int/news-room/fact-sheets/detail/measles.

Disclaimer

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.