The people at greatest risk from the virus will keep changing

Since the pandemic’s early days, vaccines have shifted the risk the virus poses to us, at a community level. Older people and health-care workers were among the first in line for the shots—a practical move to protect the people whose underlying conditions or jobs ranked them among the most vulnerable. But younger members of the community had to contend with a slower schedule, and vaccine makers are still figuring out the correct dosages for the youngest among us. That’s all shifted the virus’s burden down to uninoculated children. At the same time, the virus has been evolving into speedier and speedier forms; by the time Delta slammed the world this spring, many of its most viable hosts were at risk not because of their age or circumstances, but in spite of it.

Kids still seem relatively resilient against SARS-CoV-2 compared with adults, as they always have been. But compared with the variants that came before it, Delta is a faster spreader, and therefore a larger threat to everyone who is unvaccinated—which means children are now at greater risk than they were before.

Relative risk will keep shifting, even if the virus somehow stops mutating and becomes a static threat. (It won’t.) Our immune systems’ memories of the coronavirus, for instance, could wane—possibly over the course of years, if immunization against similar viruses is a guide. People who are currently fully vaccinated may eventually need boosters. Infants who have never encountered the coronavirus will be born into the population, while people with immunity die. Even the vaccinated won’t all look the same: Some, including people who are moderately or severely immunocompromised, might never respond to the shots as well as others. The assumptions we first had about whom the virus might hit hardest will keep changing, as will the population of people who fall ill at all.