Philip J. Goscienski, M.D.
In the two centuries since Edward Jenner vaccinated his own son against smallpox, the practice of immunization has been one of the major reasons for the elimination of some of humanity's most dangerous infectious diseases. Today's medical graduates are unlikely to ever see a patient with polio, diphtheria or measles, diseases that their grandparents knew at first hand. When one of these infections appears at all in the United States it is almost always in a traveler from the Third World. Tragically, each of these diseases occurs in occasional outbreaks, typically among children whose parents have decided not to immunize them for religious or other reasons.
When a very high percentage of a given population is immunized against a particular disease, that infection may nearly disappear. This phenomenon, called herd immunity, can lead to a sense of complacency. Some of these microbes never really disappear from the environment or they may be introduced from elsewhere, and can attack when they encounter an unvaccinated victim.
When a traveler, possibly from India, carried the polio virus into Holland in 1992, more than 70 persons became ill. There were 2 deaths and 59 victims were paralyzed. All belonged to a group that refused vaccination. There was not a single case among persons that had been immunized against polio.
The pneumococcus is a bacterium that causes serious, often fatal pneumonia in the elderly and meningitis and bloodstream infections in younger persons. After a vaccine for children against 7 strains of pneumococcus was introduced, the incidence of disease caused by those strains dropped precipitously, even in adults who had not been immunized. Because children no longer carried those strains they stopped passing them on to their relatives. A particular strain of pneumococcus, 19A, that was not included in the original vaccine actually increased as its competitors left the scene. When a revised vaccine that contained strain 19A was introduced, infections due to that strain also dropped significantly.
Hepatitis A followed a similar pattern. Children who caught the disease in a day care center showed no symptoms but they passed the virus on to their parents, who often became ill. After introduction of the hepatitis A vaccine for children, the disease plummeted among adults.
Vaccine injury does occur but the loss of herd immunity can be devastating. Ask the families of the polio victims in Holland.
Philip J. Goscienski, M.D. is the author of Health Secrets of the Stone Age, Better Life Publishers 2005. Contact him at email@example.com.