In a study published in The Lancet Regional Health – Europe researchers sought to “facilitate the selection of new RSV intervention programmes” through an assessment of cost and benefits to potential programmes. Through a dynamic transmission model, they were able to compare maternal vaccination (MV) to long-acting monoclonal antibody (la-mAB) therapy against RSV in England and Wales, calculating “impact and cost-effectiveness”. The findings indicate that both strategies could “substantially reduce the burden of RSV disease in the infant population”.
RSV: a significant global health problem
The authors state that respiratory syncytial virus (RSV) “remains a significant global health problem”, especially for infants under the age of 5, who are “particularly susceptible to severe RSV disease”. The age group represents an estimated 3.6 million hospitalisations and 101,400 deaths each year. Within this group, most of the severe disease is concentrated in infants under 6 months old, accounting for 33% of hospitalisations and 46% of deaths in children less than 5 years old.
Protection progress
The paper reflects that there has historically been only one licensed product for protection against RSV: the monoclonal antibody treatment palivizumab (Synagis), a “costly” intervention that requires monthly injections. However, recent progress has been made in the development of two new products: Pfizer’s maternal vaccine, Abrysvo, and Sanofi’s la-mAB, Nirsevimab.
The former is a bivalent prefusion F subunit vaccine that was effective at protecting against medically attended RSV disease during the first six months of life when administered to pregnant participants between 24- and 36-weeks gestational age. The la-mAB is an anti-RSV monoclonal antibody with extended half-life, targeting the surface F protein. It is 74.5% effective at reducing medically attended RSV disease up to 150 days after administration in neonates. Both have been licensed by the FDA.
Cost and benefit
The UK’s Joint Committee on Vaccination and Immunisation is the national decision maker for immunisation programmes and is informed by “clinical and operational considerations” as well as cost-effective analysis. Thus, if there are different products or programme options, assessments must analyse all programmes simultaneously. The study authors identify a “challenging question” arising from the similar efficacy but different delivery routes.
“Careful evaluation through mathematical modelling and cost-effectiveness is required.”
To answer the question, the study offers a “head-to-head cost-effectiveness comparison” of maternal vaccine and la-mAB programmes in England and Wales. It integrates a transmission model calibrated to data on RSV incidence and clinical trial data into an economic evaluation, which allowed the researchers to calculate the “optimal programme under a realistic range of purchase and administration costs”.
“We find that all large-scale programmes are effective at reducing disease burden, and when considering the population-level effects of both products, including their indirect effects, both are similarly effective at preventing RSV disease per dose. However, due to their presumed higher coverage, the la-mAB programmes prevent more disease than the maternal vaccination programmes.”
A noticeable shift
It is notable that, after the “reduction in RSV-related healthcare outcomes in infants” there was an observed “small increase” in health outcomes in the 1-year age group. This arises from an “increased age of first infection” due to a “higher proportion of susceptibles in the 1-year age group”.
“This shift is a consequence of introducing large-scale short-lived passive immunity into the population, instead of relying on active immunity that builds up an individual’s own protection.”
The age shift was “more pronounced” with la-mAB use, as the protection is longer lasting in comparison with the maternal vaccine.
“In CEA analysis [cost-effectiveness analysis], assuming low CCPA [combined cost of purchasing and administration] for both products, the la-mAB programmes emerge as the optimal choice due to their larger overall impact and favourable cost-effectiveness ratio driven by higher coverage.”
However, the authors call for consideration of “other implementation factors” such as feasibility of implementation and the CCPA of each product.
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