Statements like this are very common in anti-vaccine literature, the intent apparently being to suggest that vaccines are not needed. Improved socioeconomic conditions have undoubtedly had an indirect impact on disease. Better nutrition, not to mention the development of antibiotics and other treatments, have increased survival rates among the sick; less crowded living conditions have reduced disease transmission; and lower birth rates have decreased the number of susceptible household contacts. But looking at the actual incidence of disease over the years can leave little doubt of the significant direct impact vaccines have had, even in modern times. Here, for example, is a graph showing the reported incidence of measles since 1920.
There were periodic peaks and valleys throughout the years, but the real, permanent drop coincided with the licensure and wide use of measles vaccine beginning in 1963. Graphs for other vaccine-preventable diseases show a roughly similar pattern, with all except hepatitis B showing a significant drop in cases corresponding with the advent of vaccine use. Are we expected to believe that better sanitation caused incidence of each disease to drop, just at the time a vaccine for that disease was introduced? Furthermore, if improved sanitation has caused the drop in vaccine-preventable respiratory illnesses, why hasn’t it curbed the incidence of other respiratory illneses (such as colds and flu) that are transmitted in the same way?
Hib vaccine is another good example, because Hib disease was prevalent until just a few years ago, when conjugate vaccines that can be used for infants were finally developed. (The polysaccharide vaccine previously available could not be used for infants, in whom most of cases of the disease were occurring.) Since sanitation is not better now than it was in 1990, it is hard to attribute the virtual disappearance of Hib disease in children in recent years (from an estimated 20,000 cases a year to 1,419 cases in 1993, and dropping) to anything other than the vaccine.
Chickenpox (varicella) can also be used to illustrate the point, since modern sanitation has obviously not prevented nearly 4 million cases each year in the United States. If diseases were disappearing, we should expect chickenpox to be disappearing along with the rest of them. But nearly all children in the United States get the disease today, just as they did 20 years ago or 80 years ago. Based on experience with the varicella vaccine in studies before licensure, we can expect the incidence of varicella to drop significantly now that a vaccine has been licensed for the United States.
Finally, we can look at the experiences of several developed countries after they let their immunization levels drop. Three countries—Great Britain, Sweden, and Japan—cut back the use of pertussis vaccine because of fear about the vaccine. The effect was dramatic and immediate. In Great Britain, a drop in pertussis vaccination in 1974 was followed by an epidemic of more than 100,000 cases of pertussis and 36 deaths by 1978. In Japan, around the same time, a drop in vaccination rates from 70% to 20%-40% led to a jump in pertussis from 393 cases and no deaths in 1974 to 13,000 cases and 41 deaths in 1979. In Sweden, the annual incidence rate of pertussis per 100,000 children 0-6 years of age increased from 700 cases in 1981 to 3,200 in 1985. It seems clear from these experiences that not only would diseases not be disappearing without vaccines, but if we were to stop vaccinating, they would come back.
Of more immediate interest is the major epidemic of diphtheria now occurring in the former Soviet Union, where low primary immunization rates for children and the lack of booster vaccinations for adults have resulted in an increase from 839 cases in 1989 to nearly 50,000 cases and 1,700 deaths in 1994. There have already been at least 20 imported cases in Europe and two cases in U.S. citizens working in the former Soviet Union.
The incidence rate of hepatitis B has not dropped so dramatically yet, because the infants we began vaccinating in 1991 will not be at high risk for the disease until they are at least teenagers. We therefore expect about a 15-year lag between the start of universal infant vaccination and a significant drop in disease incidence.
This information is adapted from material that the U.S. Centers for Disease Control and Prevention published in 1996 to help physicians reassure their patients.
This page was posted on November 11, 1997.