Consider, for example, the travails of the vaccine against rotavirus, a common diarrheal disease that is spread by the fecal-oral route. The virus infects some 2.7 million American children under age five, annually, resulting in half a million physician visits, 50,000 hospitalizations, and dozens of deaths. Direct medical costs are almost $300 million, and overall societal costs amount to several times that.
The first live oral vaccine against rotavirus was approved in 1998 and, soon, was added to the list of recommended childhood vaccinations. After approximately 800,000 children in the U.S. received a million and a half doses, public health surveillance detected what appeared to be a statistical association between vaccination and a rare bowel abnormality called intussusception, a kind of telescoping of a portion of the bowel that cuts off the blood supply. Although the condition affected only about one in 11,000 vaccinees and is readily correctable with surgery, in response to a public outcry, the FDA forced the company to withdraw the vaccine from the market.
Consequently, we were without a rotavirus vaccine for years. Ironically, more recent data suggest that the vaccine does not actually increase the overall incidence of intussusception, but only concentrates the occurrences of this side effect into a shorter time period following vaccination. In other words, the overall frequency of intussusception is not greater in vaccinated children, although it seems to occur more frequently, soon after the shot.
The FDA, increasingly gun-shy about possible side effects of drugs and vaccines, required huge clinical trials, more than 72,000 children, of Mercks just-approved vaccine against rotavirus in order to be able to detect even very rare side effects before approval.
In fairness, one does need to be concerned about a new vaccine that is intended for large numbers of healthy people. Thirty years ago, the federal government attempted to administer swine flu vaccine to the 151 million Americans age 18 and over, but the program was halted after a small number of individuals suffered generalized paralysis following vaccine administration.