Healio: RSV vaccines, who should get them?
With dozens of respiratory syncytial virus vaccines and monoclonal antibodies in development, many experts agree that the next decade may finally bring new tools to prevent this major global respiratory pathogen.
Infectious Diseases in Children asked four experts — Pedro A. Piedra, MD, a professor virology, microbiology and pediatrics at Baylor College of Medicine; Jennifer E. Schuster, MD, MSCI, a pediatric infectious disease specialist at Children’s Mercy Kansas City and assistant professor of pediatrics at the University of Missouri-Kansas City School of Medicine; John V. Williams, MD, chief of the division of pediatric infectious diseases at UPMC Children's Hospital of Pittsburgh; and Peter F. Wright, MD, professor of pediatrics at the Geisel School of Medicine at Dartmouth — who would most benefit from an RSV vaccine, and why.
Schuster - RSV is a leading cause of medically attended acute respiratory illness in both children and adults aged older than 65 years, and the virus circulates annually. Primary infection typically occurs in infants and toddlers, but reinfection can occur throughout life and adults are also at risk of RSV-related morbidity and mortality. RSV is a well-suited target for vaccine development due to annual epidemics, reinfection throughout life and high morbidity and mortality among a broad range of hosts, including young children and older adults. Many vaccines are currently undergoing investigational trials.
The largest impact of RSV disease occurs in young children. In children aged younger than 5 years, RSV causes more than 2 million outpatient visits and greater than 57,000 hospitalizations annually. The majority of infected outpatient and hospitalized children are aged younger than 24 months, with hospitalization rates averaging 5.2 per 1,000 children. Most children hospitalized with RSV infection (66%-79%) were previously healthy, suggesting that an effective vaccine would likely have broad benefit to all young infants, in addition to high-risk infants, such as those with prematurity or underlying cardiopulmonary diseases. However, vaccination would need to start early in infancy to provide optimal protection to young infants.
Maternal immunization is an alternate strategy focused on protecting the youngest infants. Children younger than 6 months have the highest rate of hospitalizations (17 per 1,000 children), and hospitalization rates continue to increase as age decreases. The highest hospitalization rates occur in children aged younger than 1 month — a population that would not benefit from infant immunization but may benefit from maternal immunization. RSV antibody is effectively transferred from mother to infant transplacentally after maternal infection, so passive immunity from maternal RSV immunization, similar to maternal pertussis immunization, may be protective for infants who are too young to receive an infant RSV vaccine series. Additionally, RSV is a leading cause of febrile acute lower respiratory tract infection in pregnant women. Therefore, maternal immunization could be a beneficial strategy by providing both active and passive immunity, to mother and infant respectively.
Although RSV is commonly thought of as a childhood disease, adults have high rates of morbidity and mortality, with 177,000 hospitalizations and 14,000 deaths occurring annually in adults aged 65 years or older. In older and high-risk adults, the burden of disease in hospitalized patients rivals influenza A; in a large cohort, 15% of RSV-infected patients required intensive care and 8% died. Thus, older and high-risk adults remain another group that may benefit from an RSV vaccine.
This is an exciting time in the field of RSV. With many new vaccines in the development pipeline, we are getting closer to having an effective agent against this disease. However, further epidemiological studies are needed to determine the optimal target populations for these preventive measures.
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Jennifer E. Schuster