Uzuri Pease-Greene, right, leads a walk through the public housing complex in the Potrero Hill neighborhood of San Francisco where her family lives. She is working to have the old buildings replaced. Talia Herman for NPR hide caption

itoggle caption Talia Herman for NPR

Dr. Eric Ball examines a healthy 5-day-old patient in his office in Ladera Ranch, Calif. Ball and colleagues decided this week to take only patients whose parents follow the recommended vaccine schedule. Courtesy of Eric Ball hide caption

itoggle caption Courtesy of Eric Ball