A 4 week old is unimmunized, and has immature lungs. The chance of a bad outcome for the infant is much higher than for an older child or adult. You should make prudent decisions in regard to the environment this infant is subjected to, such as church day cares, child care centers, and other places where the risk of exposure to a case of pertussis might be greater. Shopping malls, parks, and other places where there is rapid air exchange probably are less risky. This vaccine is more effective, has less side effects, and is better tolerated.
Parents retain the right to choose to immunize their children.
If vaccine preventable disease occurs in their school, they may be required to leave school and not return until one incubation period past the diagnosis of the last case. This could be weeks in a large outbreak.