Current vaccination efforts may not be enough to prevent measles

A disease once eliminated in the United States may no longer be stoppable through current vaccination policies around the world, according to a study of measles published in BMC Medicine.

Current vaccination policies are lacking, and the effects could be seen through various countries and continents, including Australia, Ireland, Italy, the United Kingdom, and the United States are all vulnerable, according to researchers from the Bruno Kessler Foundation and Italy’s Bocconi University. Immunization efforts need to be increased and country-specific over the long haul.

“In recent years, we’ve witnessed a resurgence of measles cases even in countries where, according to World Health Organisation guidelines, elimination should already have been achieved,” Dr. Filippo Trentini, the study’s first author, said. Elimination is defined as endemic measles’ absence in a region for 12 months or longer. “This resurgence is due to suboptimal vaccination coverage levels. In Italy, where measles incidents rates were among the highest, the government has made measles vaccination compulsory for children before they enter primary school. We investigated the potential of this and other policies to reinforce immunisation rates in seven high-income countries.”

Researchers used a computer model to simulate the evolution of measles immunity over more than 40 years across seven countries. They evaluated the effects of adjusting existing immunization strategies and the segment of the population that remain susceptible to measles in high-income countries over time. Unless such changes are made, the authors predict, by 2050 only Singapore and South Korea would see susceptible populations remain under 7.5 percent — the susceptibility figure that must be maintained if measles has any hope of elimination.

“Our results suggest that most of the countries we have studied would strongly benefit from the introduction of compulsory vaccination at school entry in addition to current immunisation programmes,” Dr. Stefano Merler, study co-author, said. “In particular, we found that this strategy would allow the UK, Ireland and the US to reach stable herd immunity levels in the next decades, which means that a sufficiently high proportion of individuals are immune to the disease to avoid future outbreaks. To be effective, mandatory vaccination at school entry would need to cover more than 40% of the population.”

In the United States, researchers determined that vaccination from routine programs would have to cover more than 95 percent of the population — without fail — until 2050 if they hoped to keep the proportion of susceptible people under 7.5 percent.