They are, of course, wrong. Unimmunized children are already growing up, going to college, and falling victim to whooping cough, measles, mumps and other microbes lurking in dormitories, gyms and elsewhere. When these kids take their well-financed school-year abroad, lack of full immunization will put them at risk for infections. And as for the pacing of the immunization schedule, I can only ask parents whether they have spent any time watching their infants' behaviors. In a single day's play crawling on the floor, chewing on Fido's tail, stuffing toys shared with other toddlers into their mouths, fighting over food with siblings, or licking the cat's milk dish, they are bringing their environs into their bodies, exposing their immune systems to doses of antigens millions of times larger than are contained in all of the American Academy of Pediatrics' recommended vaccine doses combined.