Current vaccination policies may not be enough to achieve or maintain measles elimination in some countries, including the United States, according to researchers, who suggested that adding mandatory vaccination programs for children entering school could help countries achieve stable herd immunity and prevent future outbreaks.
Writing in BMC Medicine, Filippo Trentini, PhD, from the Bruno Kessler Foundation in Italy, and colleagues noted that the World Health Assembly set three milestones in 2010 with a goal of achieving measles eradication by 2015. These included increasing routine coverage with a first dose of measles-containing vaccine to more than 90% nationally, reducing the global annual incidence of measles to less than five cases per million and reducing global deaths from measles by 95% compared with 2000 estimates.
“While substantial progress towards these goals has been documented, regional elimination targets have not been met yet,” they wrote. “Measles still represents one of the main causes of child mortality in low-income countries, but it now poses serious challenges also in regions where elimination was declared in the last decade.”
Driven by several large outbreaks, the U.S. has recorded over 800 cases of measles already this year — the most since 1994, 6 years before measles was declared eliminated in the country. Measles cases have surged worldwide amid a growth in antivaccine sentiment and gaps in vaccination coverage.
Trentini and colleagues used a computer model to simulate the evolution of measles immunity profiles from 2018 through 2050 in seven countries with a two-dose measles program and high rates of primary school enrollment: Australia, Ireland, Italy, Singapore, South Korea, the United Kingdom and the U.S. According to the study, the model “accounts for country-specific demographic components, current immunity gaps and immunization activities in 2018.”
The study revealed that under current vaccination policies, only Singapore and South Korea would see the fraction of the population susceptible to measles remain below 7.5% — the level the authors assume is needed for measles elimination. It found that Australia, Ireland, the U.K and U.S. would need to increase coverage of routine vaccination programs above 95% or introduce compulsory vaccination at school entry with coverage above 40% to remain below the 7.5% threshold through 2050, according to the study. the researchers said the implementation of mandatory vaccination at school entry would be beneficial in Italy, but strategies targeting adults would also be needed to avoid future outbreaks in the country.
“We believe our findings contribute to the ongoing discussion on the most effective ways to achieve measles elimination goals and stress the importance of considering adjustments of current immunization strategies, especially in countries where these appear underperforming,” the authors concluded.
“Recent policies aimed at increasing childhood immunization rates through the introduction of compulsory vaccination are certainly producing positive effects, by raising the proportion of children protected against measles. However, additional efforts designed specifically for each country should also be put in place to successfully achieve and maintain measles elimination in the medium to long term.” – by Caitlyn Stulpin
Disclosures: The authors report no relevant financial disclosures.