Respiratory syncytial virus seasonality and its implications on prevention strategies

Abstract

With maternal and infant vaccines against respiratory syncytial virus (RSV) in development, it is timely to consider how the deployment of these vaccines might vary according to local RSV disease seasonality. In temperate regions RSV infection is predictably limited to a period of 3 to 5 months, while in tropical regions disease seasonality is often both more variable and more prolonged. Accordingly, in tropical regions a year-round immunisation schedule for both maternal and infant immunisation might be appropriate. In contrast, in temperate regions the benefit of year-round maternal immunisation would be heavily dependent on the duration of protection this provided, potentially necessitating a strategy directed at children due to be born in the months immediately prior to the RSV season. This review will consider the impact of seasonality on maternal and infant immunisation strategies against RSV, and the potential of an alternative approach of passive immunisation for all infants immediately prior to the RSV season.

Keywords: Respiratory syncytial virus; immunisation; maternal immunisation; public health; seasonality.

Figure 1.

Distribution of RSV peak month by geographic zone (n = 96 locations). The black histogram represents observations while the red curve illustrates the fit of a Gaussian density kernel. Reproduced from: Bloom-Feshbach K, Alonso WJ, Charu V, Tamerius J, Simonsen L, Miller MA, Viboud C. Latitudinal Variations in Seasonal Activity of Influenza and Respiratory Syncytial Virus (RSV): A Global Comparative Review. PLOS ONE 2013;8:e54445.

Figure 2.

Period of potential protection from RSV infection using different vaccine strategies, using UK as an example of temperate countries assuming RSV season 16th October- 12th March.

Figure 3.

Period of potential protection from RSV infection using different vaccine strategies, tropical countries.

Figure 4.

Period of benefit of vaccination strategies on hospital admissions for bronchiolitis in temperate countries (adapted from Parikh ET AL. 2017). Adapted from: Murray J, Bottle A, Sharland M, Modi N, Aylin P, Majeed A, Saxena S, Medicines for Neonates Investigator Group. Risk factors for hospital admission with RSV bronchiolitis in England: a population-based birth cohort study. PloS one. 2014 Feb 26;9(2):e89186.

Figure 5.

Suggested maternal RSV immunisation strategy by expected due date (EDD) in United Kingdom (Northern temperate climate), assuming (A) 2 and (B) 4-month period of protection from trans-placental antibodies. Assuming RSV season 16th October- 12th March. Dotted box represents potential targeted immunisation campaign for pregnant women between 16 weeks and 36 weeks gestation in the UK.