During an outbreak, aren’t the majority of people who catch a disease those who have been vaccinated?
Although vaccines have very high effectiveness rates, they are not completely effective for 100% of the people who receive them. For example, a full series of measles vaccine will protect 99 of 100 children from measles, and polio vaccine will protect 99 of 100 children from polio.2 This means that when there is a disease outbreak, the very small number of people for whom the vaccine did not work may still be able to catch the disease. Because almost all of our children are immunized, and only few are not, it can be the case that during an epidemic the majority of cases occur among children who were immunized. However, the fact remains that those who have not received the vaccine are much more likely to catch the disease.
By way of example, consider an actual measles outbreak in Colorado in December 1994.5 Out of 625 children exposed to the disease, 17 got measles. Of those 609 who had previously been vaccinated, only 10 (or 1.6%) developed measles. Of the 16 children who were not immunized, 7 (or 44%) developed measles. Thus, the risk for immunized children was less than 2% while the risk for unimmunized children was 44%.
If vaccine-preventable diseases have been virtually eliminated from the United States, why do American children need to be vaccinated?
Although many of these diseases have the potential to be eliminated, outbreaks of diphtheria, measles, and other vaccine-preventable diseases still occur.
Children who are not vaccinated against measles are 35 times more likely than immunized children to catch the disease.6 Ten years ago (during the 1989 to 1991 measles epidemic), state health departments in the United States reported 55,622 measles cases, 11,251 hospitalizations, and 125 deaths.27 Research has shown that these epidemic numbers are due to the fact that in some areas only 50% of preschool-aged children had received the vaccine.2
Without vaccines, the diseases we are now protected from will return. Thousands of children will become sick, some will have long-lasting health problems, and some will die.
Other countries do not have the same levels of immunization that we benefit from in the United States. Therefore, we must all remain protected with vaccines because dangerous diseases largely under control in the United States are only a plane ride away.
