613. Transmission of Influenza Virus in Mother and Infant Transmission Events in Nepal

Abstract

Background. Infuenza immunization of pregnant women provides protection of the infant against infuenza disease. A potential mechanism of protection is prevention of maternal illness that may result in secondary transmission to infants. We aim to characterize infuenza transmission in mother‐infant pairs. Methods. Pregnant mothers were enrolled in a randomized controlled trial of infuenza immunization in rural Nepal from April 2011 to April 2013. Mothers and infants were surveyed weekly until 180 days post‐partum for respiratory illness and mid‐nasal swabs were collected at time of illness and tested for infuenza virus by reverse‐tran‐scriptase polymerase chain reaction (RT‐PCR). We defned a transmission episode as a mother‐infant pair with an infuenza‐positive illness within 14 days of each other. Infuenza viruses were strain‐typed by RT‐PCR and/or mass spectrometry Results. Seventeen mother‐infant transmission episodes occurred with maternal illness preceding infant illness in 12 (70.6%). Of transmission pairs, 12 (70.6%) were infuenza B, three (17.6%) H3N2 infuenza A, one (5.9%) H1N1 infuenza A, and one (5.9%) unspecifed infuenza A. Five (29.4%) mothers received the infuenza vaccine. Successful strain‐typing with RT‐PCR/mass spectrometry of 11 pairs revealed that 10 (90.9%) were synonymous strains. Figure 1 shows the start of respiratory symptoms and virus type associated with infuenza illness in the 17 mother‐infant pairs. Conclusion. Mothers are an important source of infant infuenza infection. Transmission was confrmed with nearly all paired transmissions demonstrating a similar strain. The majority of transmission events occurred in nonvaccinated mother‐infant pairs.