They do it in the UK and according to the NY Times article it virtually eliminated the Salmonella bacteria threat. " Faced with a crisis more than a decade ago in which thousands of people were sickened from salmonella in infected eggs, farmers in Britain began vaccinating their hens against the bacteria. That simple but decisive step virtually wiped out the health threat. But when American regulators created new egg safety rules that went into effect last month, they declared that there was not enough evidence to conclude that vaccinating hens against salmonella would prevent people from getting sick. The Food and Drug Administration decided not to mandate vaccination of hens — a precaution that would cost less than a penny per a dozen eggs. " http://www.nytimes.com/2010/08/25/business/25vaccine.html - Seems a no brainer , non?