It’s a trend that’s not restricted to Israel. In the United States and the United Kingdom, COVID-19 has “become a disease of the unvaccinated, who are predominantly young”, says Joshua Goldstein, a demographer at the University of California, Berkeley. This shift is occurring in many countries that vaccinated older people first, and are now reaching high levels of vaccination in the adult population. It follows an earlier drop in age resulting from public-health measures to prevent the spread of COVID-19 among older people who are most at risk of severe disease, such as those in nursing homes, say researchers. And the shift has brought fresh impetus to studies of transmission and disease in younger age groups. To make better policy decisions, “it’s becoming more and more important to understand the burden of disease among children and adolescents”, says Karin Magnusson, an epidemiologist at the Norwegian Institute of Public Health in Oslo.