From the Journals

Minor measles vaccination decline could triple childhood cases



A 5% drop in use of the MMR vaccine could triple the cases of measles among children aged 2-11 years in the United States, based on data from a mathematical model published in JAMA Pediatrics.

Increased reluctance among parents to vaccinate children has led to calls for a government commission on vaccine safety, wrote Nathan C. Lo of Stanford (Calif.) University, and Peter J. Hotez, MD, PhD, of Baylor College of Medicine, Houston (JAMA Pediatr. 2017 Jul 24. doi: 10.1001/jamapediatrics.2017.1695).

The researchers sought to estimate the potential impact of reduced vaccination on public health and the economy, using the MMR vaccine as an example. They collected vaccination data from the Centers for Disease Control and Prevention, created a mathematical model, and estimated $20,000 per case of measles from a public health perspective. They simulated a measles outbreak following the importation of measles into a county in the United States, and estimated the size of an outbreak based on local vaccine coverage.
In the model population, the average baseline coverage for MMR vaccination was 93% prevalence (varying by state from 87% to 97%). The average prevalence of nonmedical exemptions was 2%; state prevalence ranged from 0.4% to 6.2%. The annual number of measles cases was 48.

Using the model, a drop in MMR vaccination as little as 5% “would result in a threefold increase in national measles cases in this age group, for a total of 150 cases and an additional $2.1 million in economic costs to the public sector,” the researchers said. By contrast, increasing national MMR coverage to 95% would reduce the number of cases by 20%, they predicted.

“These estimates would be substantially higher if unvaccinated infants, adolescents, and adult populations are also considered,” Mr. Lo and Dr. Hotez said.

The study findings were limited by the use of a model and simulation of vaccine coverage, and by restricting the study to children aged 2-11 years.

However, the results “directly confront the notion that measles is no longer a threat in the United States,” and suggest “substantial public health and economic consequences with even minor reductions in MMR coverage due to vaccine hesitancy,” they emphasized. “Removal of the nonmedical personal belief exemptions for childhood vaccination may mitigate these consequences.”

Mr. Lo disclosed funding from Stanford’s Medical Scientist Training Program; no financial conflicts were disclosed.

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