Smallpox Vaccine and Breastfeeding

Summary of use during lactation

Worldwide, three vaccines are available for smallpox, known as MVA-BN, ACAM-2000 and LC16. Only MVA-BN (Jynneos) and ACAM-2000 are available in the United States. The MVA-BN vaccine does not replicate and behaves like a non-live vaccine. The ACAM-2000 vaccine is live and is contraindicated in breastfeeding. No information is available on the LC16 (minimally replicating) vaccine during breastfeeding. The US Centers for Disease Control and Prevention and the World Health Organization state that the MVA-BN vaccine can be offered to breastfeeding women who are otherwise eligible and breastfeeding need not be discontinued after vaccination. The risks and benefits of the vaccine should be discussed with the patient using shared decision-making.[1-3]

Drug levels in milk and infant serum

Maternal Levels. Smallpox vaccine ACAM-2000 has not been studied in lactating women. Live vaccinia virus can be inadvertently transmitted from a lactating mother to her breastfed infant. Infants are at high risk of developing serious complications from live vaccinia smallpox vaccination.[4] Infant Levels. Relevant published information was not found as of the revision date.

Effects in breastfed infants

One 5-month-old breastfed infant acquired a vaccinia lesion on her upper lip, tongue and cheek after her mother developed vaccinia lesions on both areolas. The mother's infection apparently originated from the father who had been vaccinated about 10 days prior with a live vaccine (exact type not stated). The exact mechanism of transmission was not apparent.[5]

Effects on lactation and breastmilk

Relevant published information was not found as of the revision date.

Alternative drugs to consider

Monkeypox Vaccine

References

1. Centers for Disease Control and Prevention. Mpox clinical care and treatment during pregnancy. January 30, 2025. https://www.cdc.gov/mpox/hcp/clinical-care/pregnancy.html
2. World Health Organization. Smallpox and mpox (orthopoxviruses): WHO position paper, August 2024. WHO Weekly Epidemiological Record 2024;99:429–56. https://www.who.int/publications/i/item/who-wer-9934-429-456
3. Hombach J., Lewis R., Holten J. V., et al. Breastfeeding mothers in DR Congo should have access to the mpox vaccine. Lancet Glob Health 2024;12:e1932.39577965 PubMed
4. Acambis Inc. ACAM2000 (Smallpox [Vaccinia] Vaccine, Live) package insert. 2007.
5. Garde V, Harper D, Fairchok MP. Tertiary contact vaccinia in a breastfeeding infant. JAMA 2004;291:725–7.14871916 PubMed