Issues in RSV vaccination in LMICs
This seminar will explore issues related to the global implementation of vaccines targeting respiratory syncytial virus (RSV).
Infections with the RSV are an important cause of mortality in young infants in LMICs and of hospital admissions of infants and young children in HICs. There has also been increasing recognition of the morbidity caused by RSV infections in the elderly.
Early attempts to produce an RSV vaccine resulted in enhanced disease severity in vaccinated children and this set back subsequent vaccine development. However, in recent years efficacious vaccines have been developed that do not have this adverse effect and several vaccines have been trialled and licensed for use in the elderly. Of special importance in LMICs is protection in early infancy when the mortality rates from RSV infection are highest. Monoclonal antibodies are used for this purpose in high-risk infants in HICs and a recent advance has been the development of long-acting monoclonals, which give protection for around six months after a single dose. However, the cost of these is currently high which prohibits their use in most LMICs.
An alternative approach has been through maternal vaccination and several large trials have been conducted. These have had mixed results, but the most recent trial has shown high efficacy in the first six months of life and has been licensed both by the FDA and the EMA. Because the burden of RSV may be under-appreciated in many LMICs, and in order to assist countries in prioritising resource allocation, in 2022 WHO-SAGE (the main advisory group for vaccines to WHO), anticipating the near-term availability of efficacious preventive interventions, recommended an adequately sized and funded randomized, controlled study to document the full potential public health impact of these products on child health and health systems in LMICs.
The design and conduct of such a study are not without challenges, which have increased with the recent recognition of a potential safety signal, an increase in the risk of premature births, associated with the use of maternal RSV vaccines in LMIC participants in two Phase 3 trials.
Peter Smith, LSHTM
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