Respiratory Syncytial Virus (RSV) is a pervasive and highly potent pathogen which, by the tender age of two, will have infected nearly all children worldwide. Ingulfing the airway, this virus is notorious for inducing croup in the trachea, bronchiolitis in the smallest of bronchi, and pneumonia in the lungs. It is responsible for an astounding 33 million severe respiratory infections annually in children under 5 years old, marking RSV as the primary reason for pediatric hospitalizations with 3.6 million instances each year.
Sadly, RSV accounts for approximately 101,000 infant deaths yearly, of which half are younger than 6 months. Shockingly, 98% of these fatalities occur within Low and Middle Income Countries (LMIC). In many impoverished economies, children tragically succumb to the disease before even reaching a hospital, with mortality rate from RSV infection in community settings being fourfold higher than in hospitals. In fact, no other virus, including the infamous influenza, inflicts as much havoc on infants.
RSV’s potent impact on children’s health has been vividly illustrated in Malaysia. Throughout a 26-year study (1982-2008), RSV was identified as the primary virus responsible for 70.6% of all laboratory-confirmed viral LRTIs in children ≤5 years. Among RSV-infected children under 2 years old, a staggering 84.5% required hospitalization. From 2008 to 2013, 15.3% (69 out of 450) RSV-infected children admitted to Tuanku Jaafar Hospital in Seremban required intensive care and 1.6% (7/450) unfortunately did not survive. The grim case fatality rate in Malaysia is five times higher than it is in developed countries (0.3%).
Treatment for RSV is primarily supportive, involving intravenous fluids, oxygen, empirical antibiotics, and respiratory support in the intensive care unit. The burden and cost of RSV disease in LMICs is considerable; mitigating these through immunizations could hugely impact health outcomes and conserve significant healthcare resources.
Efforts to curtail this global health menace began as early as the 1960s, with research exploring varied vaccination avenues. Until 2022, only Palivizumab, a short-acting monoclonal antibody (mAb), had been licensed for prophylaxis against RSV. Administered in five monthly injections, it only prevents 55% of RSV disease, and is indicated for premature infants and those with chronic heart conditions and lung diseases. However, the vast majority of infants with RSV are term infants.
As a beacon of hope, 2023 welcomed the licensing of Nirsevimab, a long-acting mAb, which proved impressively effective at preventing RSV-related hospitalizations (83.2%) in the first 5 months of life. Real-world studies underpin its efficacy, displaying an 82-98% success rate in averting RSV-related hospitalizations and 70-90% in preventing ICU admissions. Additionally, a maternal vaccine, administered in the third trimester, has shown promising results in shielding newborns in their most vulnerable first six months of life. This vaccine demonstrated an efficacy rate of 81.8% in the first three months of life and 69.4% over the first six months. Such advancements herald a new era of improved options in the fight against this once devastating infantile disease.