In November of 2018, a few children contracted chickenpox at the Asheville Waldorf School in Asheville, N.C. By mid-November, a local newspaper reported 36 infections—the largest outbreak in the state since the chickenpox vaccine became available.
Since the introduction of the varicella vaccination in 1995, reported cases of chickenpox have significantly decreased nationwide; the Centers for Disease Control and Prevention (CDC) reports indicate that the number of cases had fallen about 90%. Yet, in the past few years, some diseases that have become less prevalent, including chickenpox, measles, and pertussis (whooping cough), have resurfaced among under-vaccinated communities, according to researchers at Emory.
While some diseases may appear to be less of a public threat as prevalence decreases, it is important for patients and the public to understand the difference between “elimination” and “eradication” of disease in order to protect themselves and their communities against vaccine-preventable diseases.
According to the CDC, a disease is categorized as eliminated when it is no longer circulating in a specific region. Measles, rubella, mumps, diphtheria and polio have all been eliminated in the U.S., largely due to the introduction of vaccination programs in the United States in the 1970s.
Elimination does not mean that the disease cannot return to the region or that live cases of the disease do not exist, but the CDC states that those cases would originate from outside the region, often reintroduced by visitors.
In 2014, a multi-state outbreak of measles associated with Disneyland in California caused CDC-reported cases in the U.S. to almost triple, jumping from 187 in 2013 to 667 in 2014. In a weekly report, the CDC classified 93% percent of the cases as importation-associated, meaning that the disease was carried into the U.S. by international travelers.
Part of the reason for the escalation of this measles outbreak was due to under-vaccination. The CDC revealed that 74% of patient cases reported were either unvaccinated or had no vaccination documentation available.
Vaccination is part what helps to move diseases from “eliminated” to “eradicated,” says the CDC. The organization also states that the eradication of disease occurs when a disease has been eliminated worldwide. The World Health Organization (WHO) reports that as of 2018 smallpox is the only eradicated disease, saving five million lives each year.
Smallpox, a disease that claimed 300 million lives in the 20th century according to WHO estimates, was eradicated by proactive and intentional vaccination response. In 1966, the World Health Assembly undertook a global program of smallpox eradication led by Dr. Donald A. Henderson. To corral and eradicate the disease, the initiative focused on surveillance—quickly identifying new smallpox cases—and ring vaccination—identifying and vaccinating those exposed to smallpox as quickly as possible. The last case of smallpox was reported to the WHO in 1977 and the organization declared the world free from smallpox in 1980.
Many eliminated diseases are considered to be candidates for eradication by the CDC, which will require a combination of research, innovation and vaccination. Yet, the role that vaccination plays in the elimination and eradication of disease should not be overlooked. In instances when patients may hesitate to vaccinate for diseases of old, clinicians and health workers have the opportunity to educate them and reinforce a commitment to vaccination to help decrease threat of vaccine-preventable diseases at a large scale.