The Epidemiology of Respiratory Syncytial Virus Infection in Auckland, New Zealand

Abstract

Respiratory syncytial virus (RSV) is a leading cause of acute respiratory infection (ARI) in young children and older adults worldwide. Preventative strategies for RSV remain limited, however, several RSV immunoprophylaxis and vaccine candidates are in development. This thesis provides evidence to inform the implementation of new RSV preventative strategies. It is divided into two broad aims: 1. To estimate the health and economic burden of RSV in Auckland, New Zealand (NZ) by socio-demographic and health factors. 2. To assess the health impact of a potential RSV vaccine/immunoprophylaxis. For the first aim, administrative data were linked to a population-based ARI surveillance project. The work showed that among children aged <5 years, RSV accounted for 40% of ARI hospitalisations, equating to a hospitalisation rate of 6/1,000 and costing on average NZ$5,040 per episode. Among adults aged ≥18 years, RSV accounted for 8% of ARI hospitalisations resulting in a hospitalisation rate of 0.2/1,000 and costing NZ$4,758 per hospitalisation. Among children and adults, RSV rates varied by age, ethnicity, and socioeconomic status. When investigating risks posed by specific chronic comorbidities (CMCs); adults with CMCs experienced a significantly increased risk of RSV hospitalisation compared to adults without the respective CMC. The risk posed by CMCs were particularly high in younger adults. In a sub-study of infants presenting to the hospital emergency department, rates of RSV-associated visits to the emergency department only were 1.5 times higher than RSV-associated hospitalisations. For the second aim, a mathematical model parametrised to RSV data from Auckland was used to assess the impact of an RSV maternal vaccine or a seasonal infant immunoprophylaxis. The model found that an RSV maternal vaccination and a seasonal immunoprophylaxis could reduce RSV hospitalisation burden by approximately 20-50% and 40-60% in children aged <2 years, respectively. Overall, a seasonal immunoprophylaxis showed a greater impact as it provided protection to a wider age range. However, a maternal vaccine offering six months of protection also reduced RSV hospitalisations among children aged 6-23 months, indicating some indirect effects, potentially making it more cost-effective than previously estimated. This thesis utilises various data sources and methods to understand the epidemiology of RSV. Findings will be useful in informing RSV disease prevention in NZ.