Live oral rotavirus vaccines have been less immunogenic and efficacious among children in poor developing countries compared with middle income and industrialized countries for reasons that are not yet completely understood. We assessed whether the neutralizing activity of breast milk could lower the titer of vaccine virus and explain this difference in vitro.
Breast milk samples were collected from mothers who were breast-feeding infants 4 to 29 weeks of age (ie, vaccine eligible age) in India (N = 40), Vietnam (N = 77), South Korea (N = 34), and the United States (N = 51). We examined breast milk for rotavirus-specific IgA and neutralizing activity against 3 rotavirus vaccine strains—RV1, RV5 G1, and 116E using enzyme immunoassays. The inhibitory effect of breast milk on RV1 was further examined by a plaque reduction assay.
Breast milk from Indian women had the highest IgA and neutralizing titers against all 3 vaccine strains, while lower but comparable median IgA and neutralizing titers were detected in breast milk from Korean and Vietnamese women, and the lowest titers were seen in American women. Neutralizing activity was greatest against the 2 vaccine strains of human origin, RV1 and 116E. This neutralizing activity in one half of the breast milk specimens from Indian women could reduce the effective titer of RV1 by ∼2 logs, of 116E by 1.5 logs, and RV5 G1 strain by ∼1 log more than that of breast milk from American women.
The lower immunogenicity and efficacy of rotavirus vaccines in poor developing countries could be explained, in part, by higher titers of IgA and neutralizing activity in breast milk consumed by their infants at the time of immunization that could effectively reduce the potency of the vaccine. Strategies to overcome this negative effect, such as delaying breast-feeding at the time of immunization, should be evaluated.
From the *National Centers for Immunization and Respiratory Disease, Centers for Disease Control and Prevention, Atlanta, GA; †Division of Pediatric Infectious Disease, Emory University, Atlanta, GA; ‡The National Institute of Hygiene and Epidemiology, Hanoi, Vietnam; §Department of Pediatrics, All India Institute of Medical Sciences, Delhi, India; ¶Department of Pediatrics, Rhode Island Hospital, Providence, RI; ∥Department of Microbiology, College of Medicine, Korea University, Seoul, South Korea; and **Fogarty International Center, National Institutes of Health, Rockville, MD.
Accepted for publication April 9, 2010.
Supported (in part) by CDC program funds. Also supported (in part) by the NIH National Center for Research Resources, grants K12RR017643 and 1KL2RR025009 (to S.A.L.).
The findings and conclusions in this report are those of the authors and do not necessarily represent the views of CDC.
Address for correspondence: Baoming Jiang, DVM, PhD, Gastroenteritis and Respiratory Viruses Laboratory Branch, National Centers for Immunization and Respiratory Disease, MS G04, 1600 Clifton Road NE, Atlanta, GA 30333. E-mail: email@example.com.