Europe needs measles vaccination push, researchers warn
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LISBON, Portugal — In 2018, Europe reported nearly 83,000 cases of measles — a 15-fold increase over 2016. Four countries lost their measles elimination status the following year amid the surge, which was linked to gaps in vaccination.
Measles elimination is considered lost when a single strain of the measles virus circulates for at least 12 months. The United States nearly lost its status in 2019 over two long outbreaks in New York, and recently published data showed that at least 35,000 children in the U.S. entered kindergarten for the 2020-2021 school year without documentation of routine immunizations, including against measles.
The COVID-19 pandemic caused a greater than 80% decline in measles cases in 2020, according to a report published last November in MMWR, but dozens of national measles vaccination campaigns also went on hold that year and 22 million infants did not receive a first dose of measles vaccine.
CDC Global Immunization Director Kevin Cain, MD, warned at the time that efforts to strengthen measles surveillance and increase measles vaccine coverage were needed to prevent a resurgence of the disease when the world emerges from the pandemic.
WHO has established targets that countries must hit to achieve measles elimination status, including at least 95% coverage with two doses of measles vaccine. According to researchers at the European Congress of Clinical Microbiology & Infectious Diseases, that should be considered the bare minimum needed to achieve elimination.
Lukas Hemmers, MSc, an epidemiologist at the State Office for Health and Social Affairs in Berlin, and colleagues noted that the strategy of achieving 95% measles vaccine coverage “assumes a very high vaccine effectiveness” of between 96% to greater than 99% and a population immunity of 91.5% to 94.4%.
Hemmers and colleagues conducted a systematic review and meta-analysis of observational studies published through April 20, 2021, to assess the vaccine effectiveness of two doses of measles vaccine. The studies were mainly from Europe and North America and included people aged older than 9 months. To be eligible for inclusion, the studies had to compare the risk or odds of measles among people who had received two doses of vaccine with those who had received none.
The 19 studies included in their analysis included 21 estimates and were all conducted during outbreaks of measles. According to a pooled estimate of the results, the effectiveness of two doses of vaccine was high at 96.4%. However, the researchers reported that population immunity in the studies — 91.6% — was only slightly higher than the 91.5% necessary under the 95% coverage strategy, if immunity conferred by one dose of vaccine is discounted.
Based on the findings, Hemmers and colleagues argued that a 95% vaccination rate “can only be the minimum requirement but not the goal for successful measles elimination.” Only six countries in Europe report two-dose measle vaccination coverage of at least 95%, making measles elimination on the continent “questionable,” they said.
“I think it's really hard to reach certain groups, for whatever reason,” Hemmers told Healio. “You don’t necessarily have to reach 95% if you have a really good case- and contact-tracing system like the U.S. has. But if you don’t have that kind of system, it is important to aim for 95% or even higher because that makes the second part of contact tracing and case finding a lot easier, because you don't have as many susceptible people to find.”
[Editor’s note: This story was updated to include comments from Hemmers.]
References:
Dixon MG, et al. MMWR Morb Mortal Wkly Rep. 2021;doi:10.15585/mmwr.mm7045a1.
Global progress against measles threatened amidst COVID-19 pandemic. https://www.who.int/news/item/10-11-2021-global-progress-against-measles-threatened-amidst-covid-19-pandemic. Published Nov. 10, 2021. Accessed April 20, 2022.
Perspective
Back to TopPeter Hotez, MD, PhD, FASTMH, FAAP
I’m concerned about two new factors that could bring back measles to the U.S. and globally. The first are the social disruptions following the COVID-19 pandemic and abrupt declines in childhood immunizations, including MMR. However, in addition, I’m also now convinced a global antivaccine movement empowered in this time of COVID-19 will now spill over to other vaccines. In this case, I worry we won’t return to baseline MMR coverage, leaving us vulnerable to future measles epidemics.
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Hemmers L, et al. Abstract 02556. Presented at: European Congress of Clinical Microbiology and Infectious Diseases; April 23-26, 2022; Lisbon, Portugal.
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