A new model estimates that people over 65 or those who are immunocompromised benefit the most from COVID-19 booster shots.
Among older adults, more frequent boosters (at least annually) do more to protect against being hospitalized for COVID-19 or dying from it, the researchers said. The results align, for the most part, with who is most at risk for bad COVID-19 outcomes — older people and those with compromised immune systems.
“We’re in the fourth year of the pandemic now, and we’re shifting toward more long-term mitigation strategies,” Hailey Park, lead author of the study who is a research data scientist at the university, said. “We know that protection from vaccination wanes, and we know that disease risk is very heterogeneous in the population. So how do we come up with a more optimal timing for boosters?”
Nathan Lo, MD, an assistant professor of medicine at Stanford University, built a model based on Centers for Disease Control and Prevention COVID-19 surveillance data and vaccine effectiveness estimates. The model predicted the frequency of COVID-19 vaccination that best thwarted severe disease in different populations of Americans.
A report detailing the model was published Wednesday in Nature Communications.
The team estimated the outcomes of people who got just one COVID-19 booster, an annual booster or if they kept up with boosters every six months. Among people over the age of 75, a yearly booster lowered annual severe infections from around 1,400 cases per 100,000 people to about 1,200 cases. When people got boosters twice a year, the model predicted that severe infections would fall to just over 1,000 per 100,000 people. The numbers are similar for those who are moderately or severely immunocompromised, and about half that reduction was in people ages 65 to 74.
For perspective, the drop in annual severe infections was 14 to 26 per 100,000 people who got annual shots or vaccines twice a year, respectively.
“These high-risk populations benefit from more frequent boosters relative to younger and healthier individuals, and I think that’s intuitive,” Lo said. “But it’s helpful to see the numbers; what is the difference in magnitude of risk?”
