Clinical Presentation, Risk Factors, and Cross-Protection from Repeated Respiratory Viral Infections in Infants in Nepal

BACKGROUND: Globally, pneumonia is the leading cause of childhood mortality, and RSV is a leading cause of viral pneumonia among children. Many respiratory viruses, including RSV, parainfluenza virus types 1–4 (HPIV), and rhinovirus (HRV) have the ability to cause repeated infections throughout a person’s lifetime. However, the incidence, clinical characteristics, and risk factors associated with recurrent RSV are not well described, particularly in low and middle income countries. METHODS: Data were collected from a randomized trial of maternal influenza vaccination conducted in rural southern Nepal from April 2011 to May 2014. Infants were followed weekly for respiratory illness until 180 days after birth. If symptomatic, a nasal swab was collected for analysis by RT-PCR for RSV and other respiratory viruses. RESULTS: HRV was the leading cause of respiratory infections with an incidence of 1071 per 1000 person-years (p-y). Incidence of RSV and HPIV were 222 and 223/1000 p-y, respectively, followed by CoV, BoV, HMPV, Flu, and AdV. Male gender, maternal smoking, and having other children at home were associated with a higher risk for any respiratory viral infection. Of the 336 infants infected with RSV, 12 (3.6%) had a second RSV infection in the first six months of life. The incidence for a secondary RSV infection was lower than the incidence for a primary infection (167 vs. 222/1000 p-y, respectively). No significant differences in severity or duration of illness were noted between the first and second RSV infections. Repeated infections with HRV, HPIV, and Flu were observed in 466 (34.8%) of 1,341 infants, 12 (3.4%) of 350 infants, and 7 (4.0%) of 177 infants, respectively. Birth between June and September conferred a protective effect against repeat respiratory viral infections. CONCLUSION: Repeated infections were observed with all the respiratory viruses tested. However, the incidence of secondary RSV infection was lower than primary infection in infants less than 6 months of age, suggesting a potential protective immune response in infants after natural infection. These data are supportive of using vaccination to protect this vulnerable population against disease. DISCLOSURES: J. Englund, Gilead: Consultant and Investigator, Research support; Chimerix: Investigator, Research support; Alios: Investigator, Research support; Novavax: Investigator, Research support; MedImmune: Investigator, Research support; GlaxoSmithKline: Investigator, Research support