Measles in Mexico, 1941-2001: Interruption of Endemic Transmission and Lessons Learned. Santos JI, Nakamura MA, Godoy MV, Lucas CA, Kuri P, and Conyer RT. Journal of Infectious Diseases 2004;189:243-250 (Suppl 1)
Could measles be eliminated in Mexico?
This study analyzed the historical distribution of measles in Mexico and evaluated the impact of measles control strategies used in that country.
Between 1989 and 1991, Mexico, like the rest of the American continent, experienced a measles pandemic. After the pandemic, the Mexican Ministry of Health implemented programs to eliminate endemic measles—the common low-level occurrence of the disease in the country.
These programs were based on the Pan American Health Organization’s strategies for measles elimination: Increasing vaccination coverage in children through 5 strategies (“catch-up”, “mop-up”, “keep-up”, “follow-up” and “push-up”); performing aggressive control measures in response to outbreaks; and developing a high-quality and specific surveillance system for cases and outbreaks.
Researchers calculated the coverage levels achieved with vaccination campaigns and evaluated the effectiveness of the measles surveillance system.
Since 1991, measles elimination efforts in Mexico have resulted in increasing coverage to more than 95% among children 1 through 6 years of age with 2 doses of either measles or measles-mumps-rubella vaccine since 1996 and in coverage of 97.6% among children 6 through 10 years of age since 1999.
Surveillance data suggest that the transmission of local measles virus was interrupted in 1997. During 1997 1999, there were no confirmed cases of measles.
After almost 4 years without measles cases, in April 2000, measles virus was reintroduced into Mexico by a Canadian visitor. Thirty laboratory-confirmed cases were reported during that outbreak.
Researchers concluded that the specific strategies adopted for measles elimination have enabled Mexico to eliminate the endemic transmission of measles.
Measles is no longer prevalent in Mexico. A few cases have been imported from other countries, but these have been controlled successfully thanks to high rates of immunization coverage and the surveillance system to detect cases.
The elimination of measles from Mexico demonstrates that high immunization coverage, aggressive case finding, with targeted immunization can eliminate local measles from a country.
This article outlines the approach led by the Pan American Health Organization that resulted in the virtual elimination of endemic measles in the Western Hemisphere. May, 2004, marked 18 months without local transmission. That is, over the past year and a half all cases of measles in the Western Hemisphere have been traced to importations from China, Japan, Europe or Africa. The most recent limited outbreaks of measles in Mexico appear to have been imported from Asia, affecting largely unimmunized infants and young adults.