With sustained vaccination campaigns, the US eliminated measles in 2000. The highly contagious virus is no longer present in the country—it is no longer endemic. Since then, measles has only emerged when travelers brought it in, causing mostly small outbreaks—ranging from a few dozen to hundreds of times each year—that have since subsided.
But all this may be about to change. With the rise of non-medical vaccine exemptions and delays, the country is regression towards endemic measles, Stanford and Baylor College of Medicine researchers warned this week. With broader disease sampling, researchers are making it clear how close we are to seeing explosive, perhaps negligible, outbreaks.
According to the results of the published researchers JAMA Pediatrics, a mere five percent drop in measles-mumps-and-rubella (MMR) vaccination rates among children ages two to 11 would triple measles cases in this age group and cost $2.1 million in healthcare costs general health. And that’s just a small slice of the spectrum of disease transmission. Children aged two to 11 alone make up about 30 percent of measles cases in current outbreaks. The number of cases would be much larger if researchers had enough data to model the social mix and immune status of adults, adolescents, and children under two.
“The results of our study find public health and economic consequences with even smaller declines in MMR coverage due to vaccine hesitancy and directly challenge the idea that measles is no longer a threat in the United States,” the authors concluded.
Researchers Nathan Lo and Dr. Peter Hotez were motivated to conduct the study after they saw data showing growing vaccine skepticism and the use of non-drug alternatives—which is due to false and incorrect information about the safety of vaccines. and the threat of infectious diseases, such as measles. . Currently, about two percent of children between the ages of two and 11 are vaccinated.
Measles, in particular, requires careful vaccination. A highly contagious virus can remain in the air for hours after coughing or sneezing. Those who are sick have a high fever, sore throat, burning eyes, and a cold-like nose and cough. But people can spread it for days before those symptoms appear. About 30 percent lead to complications, such as pneumonia, brain swelling, and blindness.
To prevent infections, the population must have between 90- and 95-percent coverage to maintain herd immunity. Many counties and regions in the US are on the verge of dipping below that level and thus losing their protection from the case of measles going, well, viral. And there is a chance for those vaccination rates to continue to slip. Currently, 18 states allow for personal belief exemptions, and all but two states allow for religious or scientific exemptions.
To estimate what will happen if vaccine exemptions continue to increase, Lo and Hotez came up with a mathematical model of measles transmission given current exemptions, data on vaccination rates from the Centers for Disease Control and Prevention Disease, and social integration patterns of children aged two to 11 (that’s the age group for which they have the most data). They also estimate the costs of measles outbreaks, accounting for medical staff wages, laboratory analyses, and outbreak surveillance.
The researchers calibrated and validated their model using past measles transmission and outbreak data from the US, England, and Wales. Then they increased the vaccine clearance rate—from one percent to eight percent—to see what would happen.
Researchers estimate that each measles case costs about $20,000. Unsurprisingly, the greater the rate of establishment, the more cases and the greater the outbreaks. Eliminating exemptions, on the other hand, would increase the country’s MMR coverage to 95 percent, well within the range required for herd vaccination.
The researchers hope that the data will inform policies on vaccine exemptions. “Every year, an increasing number of states are debating non-drug exemptions, which is a major driver of the vaccine coverage,” Lo said in a statement. “This study quantifies the consequences of an increase in measles cases and the state dollars that will be spent on personal belief exemptions that may reduce our vaccination coverage in the world.”
JAMA Pediatrics2017. DOI:10.1001/jamapediatrics.2017.1695 (About DOIs).