By Nita Duru
The approval of respiratory syncytial virus (RSV) vaccines marks a major milestone in medicine, breaking over five decades of unsuccessful attempts to find a solution for this common and dangerous respiratory virus. RSV is a leading cause of respiratory disease worldwide, especially in young children and the elderly. Previous efforts to develop an RSV vaccine faced numerous challenges, including the rapidly changing structure of the F protein on the virus’s surface. Notably, in the 1960s, a formalin-inactivated RSV vaccine resulted in severe lung inflammation during natural infections in children, leading to two infant deaths. This failure halted RSV vaccine development for many years due to safety concerns.
Advances in understanding the virus’s biology and structure have now led to multiple successful trials and, most recently, the approval of the world’s first RSV vaccine. The U.S. Food and Drug Administration (FDA) approved Arexvy on May 3, 2023, for adults aged 60 and above. The European Medicines Agency followed with approval on June 7, 2023. Additionally, on May 18, 2023, an FDA panel endorsed a maternal RSV vaccine designed to protect infants up to 6 months old when administered to pregnant women.
According to a CDC report, RSV is a common respiratory virus that infects the nose, throat, and lungs. Its symptoms can be hard to distinguish from other respiratory infections like the flu or COVID-19, but it spreads mainly in the fall and winter, peaking in December and January. RSV is the most common pathogen in infants and young children with acute lower respiratory infections, though reinfections occur throughout life. It is also said to be a major cause of severe respiratory illness in elderly adults.
A PubMed Central report states RSV is responsible for significant respiratory illness worldwide. Based on the G protein gene, it is classified into two major antigenic and genetic groups (RSV A and B). RSV is highly contagious and affects individuals of all ages. In older adults, RSV commonly causes lower respiratory tract diseases (LRTD), which can lead to life-threatening conditions like pneumonia and bronchiolitis. The U.S. Centers for Disease Control and Prevention (CDC) reports that RSV causes 60,000-120,000 hospitalizations and 6,000-10,000 deaths annually among adults aged 65 and older.
The World Health Organization (WHO) also notes that RSV affects all age groups, with the highest rates of severe disease in infants between 1 and 3 months old. Each year, RSV causes an estimated 34 million acute lower respiratory tract infections in children worldwide, with over 3 million requiring hospitalization. The virus is responsible for 66,000 to 199,000 fatalities annually, 99% of which occur in low- and middle-income countries (LMICs). RSV transmission typically follows seasonal patterns in temperate areas but can occur during rainy seasons or year-round in tropical regions.
The newly approved Arexvy vaccine, manufactured by GSK, stimulates antibodies to protect against RSV infection. While GSK’s vaccine offers protection against the RSV A strain, Pfizer’s maternal vaccine, Abrysvo, protects against both A and B strains. Data shows that GSK’s vaccine is 82% effective in preventing lower respiratory tract illness and 94% effective in individuals with underlying medical conditions.
To ensure vaccine safety and effectiveness, the WHO’s Product Development for Vaccines Advisory Committee (PDVAC) oversees the licensing and policy decision-making processes for new RSV vaccines, particularly in LMICs. The WHO’s Preferred Product Characteristics (PPCs) serve as guidelines for developers, regulators, and funders. These PPCs emphasize quality, safety, and efficacy while ensuring vaccines are suitable for widespread use. Without high programmatic suitability, the introduction and deployment of vaccines could be delayed, especially in resource-limited settings.
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