Contributed by: Dr. Collins E. M. Okoror, MBBS (Ib), MBA, PDip (HRM), FWACS (OBGYN), FMCOG, MPH (RFH)

Consultant Obstetrician and Gynaecologist, UK

Immunization during pregnancy

There is no evidence of adverse pregnancy outcomes from the vaccination of pregnant women with inactivated virus, bacterial, or toxoid vaccine. Live vaccines are generally contraindicated during pregnancy because of the theoretical risk of harm to the foetus if transmission of the vaccine strain to the foetus occurs. Live vaccines can be given during reproductive planning, prior to conception, with the advice to avoid pregnancy for at least 28 days following immunization. Pregnancy should be delayed for at least 3 months following the administration of live herpes zoster vaccine. However, when benefits outweigh this theoretical risk, vaccination with a live attenuated vaccine may be considered (e.g., during a rubella outbreak). There have so far been no significant adverse effects to the foetus associated with live attenuated vaccines including monovalent rubella vaccines, combined measles-mumps-rubella (MMR) vaccines, and oral polio vaccines. The contraindication of MMR-containing vaccines should be considered a purely precautionary measure.

Pregnancy should not preclude women from immunization as the benefits of vaccination generally outweigh the potential risks of exposure to a particular infection to the mother or her foetus/newborn if the vaccine is unlikely to cause harm.

Immunization during breastfeeding

Inactivated or live-virus vaccines given to nursing mothers do not affect the safety of breastfeeding for mothers or their infants. Live viruses in vaccines can replicate in the mother but most have been shown not to be excreted in breastmilk. Inactivated, recombinant, subunit, polysaccharide, and conjugate vaccines, as well as toxoids, pose no risk for mothers who are breastfeeding or for their infants.

There are few vaccines that should be avoided during breastfeeding. Live replicating smallpox vaccine is contraindicated in lactating women due to the theoretical risk for contact transmission from mother to infant. If post-exposure prophylaxis is required, suspend breastfeeding and close contact with baby avoided until scab falls off. Yellow fever vaccine is not recommended due to probable mother-to-baby transmission of yellow fever vaccine strain virus. Avoid oral typhoid vaccine as its safety is not known; inactivated typhoid vaccine should be used if indicated. Bacille Calmette-Guérin (BCG) vaccine should generally be avoided. Live herpes zoster vaccine should also be avoided during breastfeeding.

References:

1. Centers for Disease Control and Prevention. (2016, August). Guidelines for vaccinating pregnant women. Pregnancy and Vaccination. https://www.cdc.gov/vaccines/pregnancy/hcp-toolkit/guidelines.html
2. Ezeanolue, E., Harriman, K., Hunter, P., Kroger, A., & Pellegrini, C. (2020, March 25). General Best Practice Guidelines for Immunization. Best Practices Guidance of the Advisory Committee on Immunization Practices (ACIP). https://www.cdc.gov/vaccines/hcp/acip-recs/general-recs/index.html
3. Kimberlin, D. W., Brady, M. T., Jackson, M. A., & Long, S. S. (2018). Red Book: 2018 Report of the Committee on Infectious Diseases (31st ed.). American Academy of Pediatrics.
4. Public Health Agency of Canada. (2018, April). Immunization in pregnancy and breastfeeding: Canadian Immunization Guide. https://www.canada.ca/en/public-health/services/publications/healthy-living/canadian-immunization-guide-part-3-vaccination-specific-populations/page-4-immunization-pregnancy-breastfeeding.html#p3c3a8
5. World Health Organization. (2013). Immunization during pregnancy [Global Vaccine Safety]. WHO; World Health Organization. http://www.who.int/vaccine_safety/committee/topics/influenza/pregnancy/Jun_2013/en/