Is Influenza Vaccines safe while breastfeeding?
Here is what NIH LactMed, the U.S. National Library of Medicine's authority on medicines and breastfeeding, reports about Influenza Vaccines. This is a summary of that source — not our own verdict.
Effects on the breastfed infant
Limited data indicate that breastfeeding can enhance the response of the infant to certain vaccine antigens.[ 8 , 9 ] In a study of pregnant women who were immunized during the third trimester and breastfed their infants for an average of 14 weeks, their infants had a 36% reduction in respiratory illness with fever, and a 63% reduction in laboratory-confirmed influenza during the first 6 months of life. However, the contribution of breastfeeding compared with passive transfer of maternal antibodies during pregnancy was not determined.[ 10 ] A prospective, blinded trial in Bangladesh compared outcomes of mothers randomly assigned to receive either trivalent influenza vaccine or pneumococcal polysaccharide vaccine in the third trimester of pregnancy and their infants. Influenza-specific IgA levels were higher in the breastmilk of those immunized against influenza than pneumococcus until at least 6 months postpartum. The breastfed infants of influenza-vaccinated mothers had fewer episodes of respiratory illness with fever in the first 6 months postpartum, which was positively correlated with the extent of exclusive breastfeeding.[ 2 ] A study compared the effects of inactivated influenza vaccine (Fluzone, 2011-2012 strains) and live attenuated influenza vaccine (FluMist, 2012-2013 strains) in nursing mothers who were 28 to 120 days postpartum. The breastfed infants whose mothers received the live attenuated strain had more fussiness (60%) than those whose mothers received the inactivated vaccine (45%).[ 4 ] A retrospective medical record study of 44,132 mother-infant pairs found 141 infants had laboratory-confirmed influenza before 6 months of age. Breastfeeding alone without maternal vaccination did not reduce the risk of influenza, but mothers who were vaccinated during pregnancy and breastfed their infants had a 62% decreased risk of infant influenza. Breastfeeding enhanced the protection provided by maternal vaccination alone, which reduced the risk by 40%.[ 11 ]
Effects on milk supply
A randomized, double-blind study compared the effects of inactivated influenza vaccine (Fluzone, 2011-2012 strains) and live attenuated influenza vaccine (FluMist, 2012-2013 strains) in nursing mothers who were 28 to 120 days postpartum. A total of 248 women were included over two influenza seasons. Breastmilk IgG and IgA (H1N1 strain only), serum hemagglutination inhibition (HAI), and serum IgG responses were higher after the inactivated vaccine than after the live oral vaccine.[ 4 ] Maternal milk and infant gastric and stool samples were collected from 20 premature-delivering mother-infant pairs ranging in gestational age at birth from 26 to 36 weeks in the neonatal intensive care unit. Samples were collected at 8 to 9 days and 21 to 22 days postpartum. Results were compared to the same infant samples when the infants were given donor milk. Gastric samples were collected 30 minutes after the end of the feeding. IgA antibodies to H1N1 hemagglutinin and H3N2 neuraminidase were 3.6- and 2-fold higher, respectively, in maternal milk than donor milk feeds given at 8 9 days of postnatal age but did not differ at 21 22 days. IgM antibodies to H1N1 hemagglutinin (10- and 3-fold) and H3N2 neuraminidase-specific IgM (13- and 8-fold) were higher in maternal milk than in donor milk feeds given at 8 9 days and 21 22 days of postnatal age, respectively. H1N1 hemagglutinin-specific IgG was 2-fold higher in maternal than donor milk feeds given at 8 9 days and 21 22 days of postnatal age. H3N2 neuraminidase-specific IgG was 30% higher in maternal milk than donor milk feeds given at 8 9 days but did not differ at 21 22 days. In gastric contents, H1N1 hemagglutinin-specific IgG was 2-fold higher in maternal milk than donor feeds given at 8 9 days and 21 22 days of postnatal age. H3N2 neuraminidase-specific IgG was 30% higher in maternal milk than donor milk feeds given at 8 9 days but did not differ at 21 22 days.[ 12 ] A study of nursing mothers compared the immune responses genera
Levels in milk
Maternal Levels. A randomized, double-blind study compared the effects of inactivated influenza vaccine (Fluzone, 2011-2012 strains) and live attenuated influenza vaccine (FluMist, 2012-2013 strains) in nursing mothers who were 28 to 120 days postpartum. A total of 248 women were included over two influenza seasons. No vaccine or wild-type influenza virus was detected in breastmilk of any of the women.[ 4 ] Twenty-six nursing mothers collected milk samples just before and 2 weeks after receiving a seasonal influenza vaccine during the 2019-2020 and 2020-2021 flu seasons. Thirteen study participant milk sample pairs per influenza season were assessed for specific IgA, IgG, and secretory antibody (sAb) binding against each relevant HA strain included in either the 2019-2020 or 2020-2021 seasonal influenza vaccine. Across the 7 immunogens examined, as many as 54% of samples exhibited no sAb boost, and no significant differences were found in IgG- or IgA-mediated influenza neutralization activity between the prevaccination and post-vaccination timepoints.[ 6 ] Infant Levels. Relevant published information was not found as of the revision date.
Source: NIH LactMed (National Library of Medicine).
Educational summary of an authoritative source — not medical advice. Never start, stop, or change a medicine while breastfeeding without confirming with your doctor.