Respiratory Syncytial Virus: Reasons for Optimism About a Dreaded Childhood Disease

[This article has been originally published in Spanish in El País-Planeta Futuro. It has been written by Azucena Bardají, physician and associate research professor in the Maternal, Child and Reproductive Health Initiative at ISGlobal, and Anna Lucas, coordinator of the Maternal, Child and Reproductive Health Initiative at ISGlobal.]

In recent weeks, various media outlets have reported on the apparent convergence of three epidemics: COVID-19, influenza and respiratory syncytial virus (RSV). This “tripledemic” has already overwhelmed hospital paediatric units in some countries. We have already heard a lot about influenza and COVID-19, but what is RSV and how does it affect children?

RSV causes infections of the lungs and the respiratory tract. It is so common that most children become infected with the virus by the time they reach two years of age. The symptoms are usually mild, similar to those of the common cold. In severe cases, however, RSV can spread to the lower respiratory tract, causing pneumonia or bronchiolitis (inflammation of the small airways in the lungs).

RSV is a problem affecting children’s health on a global scale: it is the leading cause of severe acute respiratory illness worldwide. More than 97% of RSV deaths in children occur in low- and middle-income countries (LMICs), mostly outside of hospital settings. In other words, most deaths occur in the children’s communities, where they have no access to oxygen or respiratory therapy. This underscores, yet again, the unequal access to and quality of child health care in large swaths of the world. RSV is estimated to cause 100,000 child deaths each year—about half in children under six months of age—and more than 3.6 million hospitalisations.

Since 2016, the World Health Organisation (WHO) has been spearheading a process to support the formulation of global RSV policies, increase knowledge about this respiratory virus and support LMICs in their decisions about the future introduction of preventive interventions. After decades of stagnation, researchers are now seeing reasons for optimism: more than 20 RSV vaccine candidates are currently in clinical development—with promising results. Of the many options currently being developed to protect infants from severe RSV infection, new long-acting monoclonal antibodies and maternal vaccines are the products best positioned for authorisation in the near future.

In accordance with a strategy based on the natural transfer of antibodies from the pregnant woman to the foetus, maternal vaccines are designed to be administered to mothers. This approach is also used for other vaccines administered to pregnant women (tetanus, pertussis, influenza and SARS-CoV-2).

However, despite this optimism, there are still gaps in our knowledge about the effectiveness of monoclonal antibodies and maternal vaccines in LMICs. We are in urgent need of information regarding programmatic issues—which are not to be underestimated—that could affect the effectiveness of maternal vaccines in under-resourced health systems or in the context of comorbidities (malnutrition, HIV, malaria). Further analysis is also required on the potential administration of monoclonal antibodies in these settings (home births, doses at birth or at the first vaccination visit, cost, etc.). These findings will inform decision-making in the countries that bear the largest burden of RSV disease and death.

In the short term, the introduction of maternal vaccines and monoclonal antibodies could significantly help to improve child survival in developing regions, especially in the first year of life, which is when 75% of all child mortality occurs. This is the age range in which the least progress has been made. Nevertheless, a successful strategy will require greater awareness and knowledge of RSV and the available preventive products on the part of decision-makers and authorities responsible for health policy in order to guide their decisions on the introduction of these tools. This issue deserves high priority on the global child health agenda in the coming years.