Live attenuated influenza vaccine (LAIV) and inactivated influenza vaccine (IIV) are licensed for use in breastfeeding women. Little is known about the transmission of LAIV viruses to the breastfeeding infant and about comparative serum and breast milk immune responses to LAIV and IIV.
A randomized, double-blind trial compared the safety and immunogenicity of LAIV with IIV in breastfeeding mothers and their infants. Healthy, 18-49 year old postpartum women and their healthy term infants were enrolled during the 2011-12 and 2012-13 influenza seasons. Women were randomized to receive the seasonal LAIV + intramuscular placebo, or seasonal IIV + intranasal placebo on Day 0. Breast milk and nasal swabs (from women and infants) were collected on Days 0, 2, and 8. Women and infants were assessed on Day 28.
· Post-vaccination reactogenicity in immunized women and clinical symptoms in their infants.
· Intranasal detection of LAIV viruses in infants.
· Breast milk and serum immune responses to LAIV compared to IIV in women.
During the 2011-13 influenza seasons in the United States, 248 women (249 infants) were enrolled. Increased irritability was reported among infants of women who received LAIV (p=0.05). Increased rhinorrhea was reported among infants of women who received IIV (p=0.02). Influenza vaccine viruses were not detected in breast milk. One asymptomatic infant had LAIV H1N1 and H3N2 by nasal swab PCR 2 days following maternal immunization. This infant's mother also had LAIV influenza A virus detected by PCR. Breast milk IgG titers were higher in IIV compared to LAIV recipients for all influenza vaccine virus strains over both seasons (p≤0.0002). The breast milk IgA response to California H1N1 was higher in IIV compared to LAIV recipients (p=0.003). IIV recipients produced higher geometric mean titers of serum hemagglutination inhibition antibodies (HAI) than LAIV recipients for each influenza season and over both seasons aggregated against all influenza vaccine strains (p<0.05).
Breast milk immunoglobulin A and G responses and serum HAI responses were higher in IIV compared to LAIV recipients. Asymptomatic transmission of vaccine virus to an infant of a LAIV recipient was noted in one instance.
S. E. Frey, None
A. L. Shane, None
E. Walter, Novartis: Investigator and Scientific Advisor , Research support
Novavax: Investigator , Research support
bioCSL: Investigator , Research support
GlaxoSmithKline: Investigator , Research support
Merck: Consultant and Investigator , Consulting fee and Research support
G. Swamy, None
E. P. Schlaudecker, None
M. C. Steinhoff, None
R. Mason, DMID, NIAID, NIH: Employee , Salary
S. Chang, DMID, NIAID, NIH: Employee , Salary
M. Wolff, The EMMES Corporation: Employee , Salary
M. Mcneal, None