In long-awaited data, Pfizer said its 3-dose vaccine was 80% effective against symptomatic omicron COVID-19 infection among children 6 months to under 5 years old. The company cautioned that estimate was preliminary and could be adjusted as more data is collected. The trial wasn't big enough to estimate protection against severe disease, which experts expect to be higher. The news doesn’t change the overall timeline for when vaccines for this age group could be available. For the youngest Americans, vaccines from both Pfizer and Moderna are expected to be authorized in June or July, likely as a three-dose vaccine for...