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Measles incidence remains low in US
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The annual rate of measles in the United States varied from 2001 to 2015 but remained “extremely low” compared with other countries, according to researchers.
Nakia S. Clemmons, MPH, of the CDC’s Division of Viral Diseases, and colleagues reported that a failure to vaccinate, rather than a lack of vaccine efficacy, is driving measles transmission in the U.S.
“Most parents are protecting their children from measles by getting the measles-mumps-rubella (MMR) vaccine for their children. Thanks to high vaccination rates, measles cases among Americans has remained rare since the disease was eliminated in the United States in 2000,” Clemmons told Infectious Disease News. “However, measles outbreaks can and do still occur in the United States. Unvaccinated U.S. residents returning from overseas travel and foreign visitors to the U.S. may develop measles and expose people in United States.”
Measles incidence varies, declines with age
Clemmons and colleagues analyzed reports of confirmed measles cases in the U.S. from January 2001 to December 2015. They identified 2,012 cases. Among them, 1,789 occurred in U.S. residents (median age, 15 years; 47.1% women). Most cases were acquired in the U.S. (73.4%) and occurred among patients who were not vaccinated (69.5%) or did not know their vaccination status (17.7%). Thirteen outbreaks of 20 or more cases were reported, 10 of which occurred after 2010.
The overall rate of measles incidence was 0.39 (95% CI, 0.37-0.41) per million population, which was much lower than the worldwide incidence rate of 40 cases per million population, according to the researchers. Measles rates were highest in infants aged 6 to 11 months (5.44 per million population; 95% CI, 4.67-6.34) and toddlers aged 12 to 15 months (5.38 per million population; 95% CI, 4.45-6.51). Rates began to decline with age at 16 months.
The number of measles cases varied each year between 24 and 658; however, a higher incidence of measles was observed over time, with 0.28 cases (95% CI, 0.22-0.35) per million population in 2001 and 0.56 cases (95% CI, 0.48-0.65) in 2015 (P < .001). During the same time period, the proportion of imported cases decreased from 46.6% (95% CI, 37.2%-56.1%) to 14.7% (95% CI, 10%-20.5%), and vaccinated cases decreased from 29.6% (95% CI, 20%-40.8%) to 20.2% (95% CI, 14.6%-26.9%; P < .001).
“This study underscores the importance of maintaining high vaccine coverage throughout the population to protect those who can be vaccinated and those who cannot, as well as maintaining a strong public health infrastructure that can quickly detect measles cases and rapidly respond,” Clemmons said. “We encourage clinicians to take every opportunity make sure their patients are up to date on all their recommended vaccines.”
Measles in Europe
Although progress has been made toward eliminating measles in Europe, health officials are calling for improvements in vaccination coverage.
WHO recently reported that 42 of 53 countries (79%) in the WHO European Region are no longer endemic for measles, as of Sept. 26. The disease has been eliminated in Croatia, Denmark, Greece, Iceland, Lithuania, Montenegro, Spain, the United Kingdom and Uzbekistan. However, WHO said more than 11,000 measles cases still occurred in the WHO European Region so far this year. In addition, regional coverage with the first dose of measles vaccine has decreased from 95% in 2012 to 93% in 2016.
According to Zsuzsanna Jakab, PhD, WHO regional director for Europe, one in 15 children in Europe do not receive the first dose of MMR on time.
“Outbreaks continue to cause unnecessary suffering and loss of life, and routine immunization coverage is decreasing,” she said in a press release.
At least 95% of vaccination coverage is needed to protect the population from measles, according to WHO. Barriers to vaccination include vaccine shortages, inconvenient access to vaccination services, and vaccine hesitancy among parents and “insufficiently informed” health care workers.
“This Region has eradicated polio, eliminated malaria and drastically reduced the transmission of measles and rubella. With continued commitment and hard work, we will be the generation that also eliminates measles and rubella from the remaining endemic corners of this region,” Nedret Emiroglu, PhD, director for health emergencies and communicable diseases of WHO’s European Region, said in the release. “This is not only our contribution but also our obligation to the generations that follow us.” – by Stephanie Viguers
References:
Clemmons NS, et al. JAMA. 2017;doi:10.1001/jama.2017.9984.
WHO. Measles no longer endemic in 79% of the WHO European Region. http://www.euro.who.int/en/media-centre/sections/press-releases/2017/measles-no-longer-endemic-in-79-of-the-who-european-region. 2017. Accessed Oct. 3, 2017.
Disclosures: The authors report no relevant financial disclosures.