RSV vaccination in third trimester associated with significantly reduced infection risk in early months of life

1. With 70% vaccination coverage, a 3^rd trimester maternal vaccine for respiratory syncytial virus (RSV) was modelled to reduce RSV infection rates by 16.6% in infants younger than 3 months. 

2. Incidence rate of RSV infections in the first 6 months of life for infants born to unvaccinated mothers was 1.26 times that of those born to vaccinated mothers.

Evidence Rating Level: 2 (Good)

The respiratory syncytial virus (RSV) infects almost all children by their second birthday, and was responsible for 3.2 million hospitalisations in the year 2015 alone globally, for children younger than 5. Although there is currently no approved RSV vaccine, maternal immunisation in the third trimester of pregnancy ubiquitously used as a preventative strategy. However, RSV vaccines are expected to be short-lasting, making it important to study their public health implications through modelling frameworks. From past research, households have been identified as a significant contributor to RSV transmission, but modelling studies have not been conducted on high-income settings yet. The current study’s goal was to model the household-level impact of maternal RSV vaccines in a high-income country. This involved combining Australian census data with a model for RSV transmission, accounting for household and community population mixing, and defining the parameters for an infant’s immunity duration, which was found to depend on vaccination timing and the mother’s immunity duration. Overall, the results found that the largest benefit from maternal vaccination was for infants younger than 3 months, with a 16.6% reduction in infection incidence (interquartile range -14.2 to -19.8%), for a scenario of 70% vaccination coverage. For infants aged 3-6 months, the reduction was 5.3% (IQR -7.3 to 1%). All other age groups had similar incidence rates compared to no vaccination scenarios, with the exception of children aged 1-2, which had a predicted 2.8% increase in infection (IQR 0.3-5.8%). In conclusion, this study showed that maternal RSV vaccination can have a significant effect on lowering infection rates in infants younger than 3, but may have little impact in older age groups.

Click to read the study in BMC Medicine

Image: PD

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