Why Do People Still Die from Vaccine-Preventable Disease?

Vaccines are one of the greatest success stories in the history of public health.

In the era of modern medicine, vaccines have combated pandemics and saved millions of lives. In the case of smallpox, for instance, a vaccine completely eradicated a fatal disease.

So, why are deaths from vaccine-preventable diseases on the rise in the 21^st century, particularly in the past decade? To find out, a team of researchers recently evaluated the relationship between vaccine refusal and the epidemiology of 2 vaccine-preventable diseases with recent outbreaks in the United States: measles and pertussis.

Measles

The first measles-containing vaccine was licensed for use in the United States in 1963. Three intensive immunization efforts were carried out over the next several decades, dramatically reducing the incidence of the disease.

In the last few years of the 1990s, the incidence of measles was fewer than 1 case per 1 million US individuals. As of January 2000, measles was considered eliminated in the United States.

Since then, there have been 1416 measles cases reported in 9 annual disease summaries and 9 outbreak reports. More than half (56.8%) of those cases lacked any history of measles vaccination.

Detailed measles vaccination data were available for 970 of the reported cases. Of those individuals, 574 (59.2%) failed to receive vaccination despite being eligible for the vaccine, and 405 (70.6%) of them had nonmedical exemptions to vaccination. The most common reasons provided were religious or philosophical beliefs, rather than true medical contraindications.

Unvaccinated children were 35 times more likely to contract measles than their vaccinated peers. Furthermore, communities with higher rates of exemption were associated with a greater incidence of measles cases.

Pertussis

A whole-cell pertussis vaccine was first introduced in the United States in the mid-1940s. The vaccine reduced pertussis incidence to a record low of 1010 US cases in 1976, after which cases of pertussis slowly began to rise. Since the early 2000s, more than 10,000 cases have been reported annually, with upwards of 25,000 annual cases seen in the past 3 years.

In the 5 largest statewide epidemics reported, up to 45% of individuals were not vaccinated. Furthermore, in 8 of the outbreaks, up to 93% of the unvaccinated were intentionally not vaccinated.

Those who had vaccine exemptions or received fewer vaccines than recommended had higher rates of pertussis than those who were adequately vaccinated. Not surprisingly, states, communities, and schools with higher rates of exemption, as well as those with allowances for personal belief exemptions or easier exemption policies, had higher rates of pertussis.

Conclusion

The researchers concluded that a substantial proportion of measles cases in the United States in the post-elimination era were a result of intentional vaccination exemption. Additionally, vaccine refusal was associated with an increased risk of pertussis.

Reference

Phadke VK, Bednarczyk RA, Salmon DA, Omer SB. Association between vaccine refusal and vaccine-preventable diseases in the United States: a review of measles and pertussis. JAMA. 2016;315(11):1149-1158.