Clinical relevance of prevention of respiratory syncytial virus lower respiratory tract infection in preterm infants born between 33 and 35 weeks gestational age.

Premature infants are vulnerable to severe respiratory syncytial virus (RSV) lower respiratory tract infection (LRTI) resulting in hospitalisation and the potential for longer-term respiratory morbidity. Whilst the severity and consequence of RSV LRTI are generally accepted and recognised in infants born <or=32 weeks gestational age (GA), there is less acknowledgment of the potential consequences in infants born 33-35 weeks GA. However, there is a growing body of evidence suggesting that infants born between 33 and 35 weeks GA may be equally at risk for RSV LRTI as infants born <32 weeks GA. Interrupted lung development and an immature immune system have been linked with an increased susceptibility for RSV LRTI, along with other environmental, social, and physiological risk factors. Currently, the only effective method of preventing RSV LRTI is prophylaxis with palivizumab. Often with limited healthcare resources, identifying infants at greatest risk of RSV LRTI who would potentially benefit most from prophylaxis is highly desirable, particularly in the 33-35-week GA group. The purpose of this article is to examine the causes and consequences of RSV LRTI in infants born 33-35 weeks GA, and look at the potential for using risk factors to identify high risk infants and, thereby, optimise prophylaxis. The causes and consequences of RSV LRTI in infants born 33-35 weeks GAA were determined via literature review. A number of underlying risk factors that significantly increase the risk of severe RSV LRTI and subsequent hospitalisation in this group of infants have been identified, most notably from the FLIP and PICNIC studies. A European predictive model based on the risk factors in the FLIP study has recently been developed and validated, which will aid identification of infants born between 33 and 35 weeks GA with the highest risk of RSV hospitalisation. Implementation of this model and prophylaxis of infants born between 33 and 35 weeks GA should be a national or regional decision, taken in perspective of other public health needs.