A potential new vaccine for respiratory syncytial virus, or RSV, would have the greatest impact if allocated primarily to children under five, a new study led by the Yale School of Public Health shows.
RSV is one of the world’s leading causes of respiratory tract infections, yet there is currently no clinically available vaccine that effectively treats the virus. RSV is particularly dangerous for the young and the old: it is the most common cause for infant hospitalization in the U.S., and is responsible for 10,000 deaths among the elderly every year.
A team led by Dr. Dan Yamin developed a first-of-its-kind transmission model for RSV to evaluate how a potential vaccine might be best administered. The findings, published in the Proceedings of the National Academy of Sciences, indicate that focusing vaccination on young children under the age of five would be the most efficient way to limit the spread of RSV not only in children, but in vulnerable adults as well.
“We found that Younger age groups—in particular, children under five—were the groups in which a single case would typically transmit the disease to more than one individual,” said Dr. Yamin, a former research scientist at Yale and now a senior lecturer at Tel Aviv University in Israel. “Accordingly, our model predicts that children are predominantly responsible for transmission, and should therefore be targeted for the benefit of themselves and the elderly.
RSV vaccines in development are mainly targeted either to young children or older adults. The study’s model analyzed the two main drivers for RSV transmission: viral load and social contact in order to identify which age group would make the most effective target for vaccines. Using data on daily viral load and weekly incidence rates of the virus from California, Colorado, Pennsylvania and Texas, the team showed that an infected child under five is more than twice as likely as an adult over the age of fifty to transmit the virus. Additionally, indirect protection indicates that focusing on vaccinating children does more to protect the elderly against RSV than directly vaccinating the elderly themselves.
The study found that because children have higher viral loads than adults, and because of frequent prolonged contact with both adults and children of their own age, they are disproportionately responsible for transmitting RSV. Although children under five represent less than ten percent of the total U.S. population, vaccinating this group could reduce as much as 75 percent of RSV infection in children and the elderly combined.
“These kinds of predictive modeling studies play a really important role in public health,” said Dr. Jeffrey Townsend, a co-author of the paper and an associate professor in the Department of Biostatistics at Yale. “They ensure that we make the right health policy decisions before implementation—saving many lives and improving quality of life.”
The World Health Organization has stated that developing a vaccine for RSV is a priority, and a vaccine for RSV is estimated to be available in the next five to ten years. The study results have the potential to inform ongoing clinical trials evaluating RSV vaccines currently in development. They may also guide future recommendations on RSV vaccinations once a vaccine is approved, underscoring the importance of looking at the effectiveness of vaccines not only among individuals, but populations as well.