Incidence of Respiratory Syncytial Virus Bronchiolitis in Hospitalized Infants Born at 33-36 Weeks Gestational Age Compared with those Born at Term: A Retrospective Cohort Study

Greenberg D, Dagan R, Shany E, Ben-Shimol S, Givon-Lavi N.

A retrospective cohort study conducted in Soroka, Israel that compared the incidence rates of RSV Bronchiolitis among pre term (33-36 weeks gestational age) children, and those born at term. Rate of bronchiolitis in the general population were extrapolated from the numbers collected in hospital. 374 late preterm and 2948 term infants were hospitalised with bronchiolotis throughout the course of the study, with 229 (61.2%) and 1738 (59%) of these having been tested for RSV respectively. Of these it was found that 164 (71.6%) pre-term infants and 1,266 (72.8%) term infants were positive for RSV respectively. When this was adjusted for population size mean yearly incidences per 1,000 children of RSV bronchiolitis hospitalizations of pre-term and term infants were calcuated to be 35.8±13.0 and 19.6±4.1, with a mean difference in incidence ratio of 1.82 between the two groups. Pre-term infants were also found to be hospitalised for significantly longer periods (4.8±7.0) in pre-term and 3.9 ±4.9 in term infants.

This study shows the staggering difference in bronchiolitis rates between even late pre-term children and those born at term, and cements the importance of a treatment strategy that captures even children with severely under-developed immune systems, such as maternal vaccination. While useful, capturing this information at a single hospital in a single country limits the applicability of these data due to the large degree of variation in incidence of RSV bronchiolitis worldwide.  Children with co-morbidities were excluded from this study, however it may have been useful to include them, or to perform a similar retrospective study at the same site in future to pick apart the relative contribution of different co-morbidities to the likelihood of developing severe disease.

Full article on PubMed.