Everyone agrees that vaccine-preventable diseases are less prevalent now than they were before vaccines were introduced. However, the myth still circulates that the diseases were disappearing before we had the vaccines. Nothing could be farther from the truth, to which anyone whose medical career has spanned the demise of H. influenzae type b can testify.
In the early 1980s, 1 in 200 children, year in and year out, were affected by invasive H influenzae disease. Call nights in the hospital were replete with cases of bacteremia, meningitis, periorbital cellulitis, and the like. Today’s pediatric residents have never seen a case—and the change occurred in the early 1990s, after the institution of universal infant Hib immunization. There is an undeniable association between the introduction of new vaccines and the beginning of the end of the respective diseases, as has been seen in the last 2 decades with varicella, hepatitis A, and S. pneumoniae.
Now that many of these diseases are rare, it is hard for parents and patients to understand why vaccines are still important. Here are a few reasons.
- Some diseases are still prevalent—Despite our successes, many vaccine-preventable diseases are still around. The choice not to vaccinate against pertussis, for example, is a choice to take a significant risk of getting the disease. The same is true for S. pneumoniae. Influenza still kills 36,000 people every year in the United States, and HPV is still highly prevalent.
- Diseases could easily re-emerge—Some diseases continue to circulate at very low levels. If immunization rates decrease, outbreaks are likely to occur. This is exactly what happened between 1989 and 1991 in the United States, when 55,622 cases of measles and 123 deaths from the disease were reported. The single most important contributing factor was low vaccine coverage, especially among preschoolers in inner cities. By 2003, after renewed efforts to achieve universal vaccination and the implementation of a 2-dose schedule, measles was no longer endemic in the United States. This means that there was enough population immunity to prevent sustained transmission, but the situation could change dramatically if coverage rates fall. The outbreak of >6000 cases of mumps in the Midwest in 2006 is further evidence that diseases can re-emerge.
- Infections can easily be imported from other parts of the world—Diseases such as polio and diphtheria still occur in other countries. Tourism, immigration, and international business travel contribute to the ease with which these diseases can be imported into the United States. The outbreaks of measles that occurred in the United States in 2008 were probably due to importation from Europe.
- Some diseases cannot be eradicated or extinguished—Tetanus, which is acquired from the environment as opposed to person-to-person transmission, is a good example.
—Marshall, Gary S. “Addressing Concerns About Vaccines.” The Vaccine Handbook: A Practical Guide for Clinicians. 3rd ed. New York: Professional Communications, Inc., 2010. 208-209. Print.