Effects of parental and household smoking on the risk of respiratory syncytial virus (RSV) hospitalisation in late-preterm infants and the potential impact of RSV prophylaxis

Objective: To assess the impact of household smoking and palivizumab prophylaxis on the risk of respiratory syncytial virus (RSV) hospitalisation in late-preterm (32-35 weeks' gestational age) infants. Methods: Familial smoking and other RSV risk factor data from the FLIP, FLIP-2 and IMpact studies and datasets from France, Germany and Italy, together with palivizumab prophylaxis data from the FLIP-2 and IMpact studies, were analysed using cross-correlation and Bayesian meta-analytical modelling employing Markov Chain Monte Carlo sampling. Results: There were 2.35 times (95% confidence interval [CI] 1.37-4.02) as many hospitalisations amongst infants from smoking compared with those from non-smoking families. Among non-prophylaxed infants, there were 2.53 times (95% CI 1.27-4.94) as many RSV hospitalisations from smoking than from non-smoking families and that excess hospitalisation was reduced to 1.03 times (95% CI 0.38-2.99) amongst prophylaxed infants. Familial smoking correlates significantly (p < 0.01) with other RSV risk factors: positive correlation with number of school-age siblings, history of family atopy, family wheeze and gestational age; negative correlation with birth weight and breast feeding. Conclusions: Late-preterm infants from smoking families appear to be at heightened risk for severe RSV infection requiring hospitalisation of which the risk may be reduced with RSV prophylaxis.