WHO Preferred Product Characteristics for Respiratory Syncytial Virus (RSV) Vaccines

Overview

Respiratory Syncytial Virus (RSV) is a leading cause of respiratory disease globally. The virus causes infections at all ages, but young infants have the highest incidence of severe disease, peaking at 1–3 months of age. By 2 years of age, virtually all children will have been infected. RSV has been estimated to cause 34 million acute lower respiratory tract infections (LRTI) in young children annually, with over 3 million severe cases requiring hospitalization, and between 66,000 to 199,000 fatalities, 99% of which are in low- and middle-income countries (LMICs). RSV transmission follows a marked seasonal pattern in temperate areas with mid-winter epidemics, but may occur during rainy seasons or year-round in the tropics.

RSV vaccine research and development activities have increased significantly in recent years. Vaccine development efforts had previously been slowed following reports from clinical trials conducted in the 1960s, in which a formalin-inactivated whole virus vaccine (FI-RSV) led to enhanced RSV disease (ERD) in children who subsequently were naturally infected for the first time with RSV. While the pathogenesis of ERD is not completely understood, strategies have been developed to reduce the risk and support further candidate vaccine development.

The World Health Organisation (WHO) Product Development for Vaccines Advisory Committee (PDVAC) considers it a priority to ensure that emerging RSV vaccines are suitable for licensure and meet policy decision-making needs to support optimal use in low- and middle-income countries in addition to high-income countries. The WHO Preferred Product Characteristics (PPCs) described in this document were developed to provide guidance to scientists, regulators, funding agencies, and industry groups developing vaccine candidates intended for WHO prequalification (PQ) and policy recommendations. PPCs do not replace existing requirements related to WHO programmatic suitability for PQ, but are intended to complement them. In addition to meeting quality, safety, and efficacy requirements, it is also important that developers and manufacturers are aware of WHO’s preferences for parameters that have a direct operational impact on immunization programs. Low programmatic suitability of new vaccines could result in delaying introduction and deployment.