ALICE McCARTHY—According to the World Health Organization, older people and people with preexisting medical conditions appear to be more vulnerable to becoming severely ill with COVID-19.
“Elderly individuals have a different immune system than healthy middle-aged adults and often do not respond as robustly to immunization, so a one-size vaccine does not fit all,” said Ofer Levy, professor of pediatrics at Harvard Medical School and director of the PVP.