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Review of regional measles surveillance data in the Americas, 1996-99
B S Hersh1, G Tambini, A C Nogueira
1Division of Vaccines and Immunization, Pan American Health Organization, Washington, DC, USA.
Background:
In 1994, ministers of health of countries of North and South America established the goal of measles eradication from the western hemisphere by 2000. To accomplish this goal, the Pan American Health Organization (PAHO) developed an enhanced measles vaccination strategy.
Methods:
PAHO's measles eradication vaccination strategy has evolved into three principal components; a catch-up measles vaccination campaign, maintenance of high vaccination coverage (keep-up), and periodic follow-up measles vaccination campaigns. To monitor progress towards measles eradication, measles surveillance has been strengthened, including the laboratory investigation of suspected measles cases.
Findings:
Both the catch-up and follow-up mass campaigns achieved high vaccination coverages in the respective targeted age groups. In 1996, only 2109 confirmed measles cases were reported in the Americas. In 1997, there was a resurgence of measles in the Americas, mostly as a result of a large measles outbreak with over 42000 cases, which occurred mainly among unvaccinated young adults in Sao Paulo State, Brazil. By 1998, there was a reduction in the number of reported confirmed measles cases, with a total of 14474 cases. Reduction of cases continued to the end of 1999, with a total of only 2828 confirmed cases.
Interpretation:
PAHO's measles eradication strategy has been effective in interrupting transmission and maintaining the absence of measles virus circulation in most parts of the Americas. The PAHO experience provides strong evidence that with full implementation of an appropriate vaccination strategy, measles transmission can be effectively interrupted.
Insights
The Pan American Health Organization's (PAHO) enhanced measles vaccination strategy effectively reduced measles cases in the Americas. This strategy, involving catch-up and follow-up campaigns, demonstrates the power of vaccination in disease eradication efforts.
Area of Science:
- Public Health
- Epidemiology
- Vaccinology
Background:
- Established in 1994, the goal was measles eradication in the Western Hemisphere by 2000.
- The Pan American Health Organization (PAHO) developed an enhanced measles vaccination strategy to achieve this goal.
Purpose of the Study:
- To evaluate the effectiveness of PAHO's enhanced measles vaccination strategy.
- To assess the impact of vaccination campaigns on measles transmission in the Americas.
Main Methods:
- Implementation of a three-component strategy: catch-up campaigns, sustained high vaccination coverage (keep-up), and follow-up campaigns.
- Strengthened measles surveillance, including laboratory investigation of suspected cases.
Main Results:
- High vaccination coverages achieved in targeted age groups during mass campaigns.
- Significant reduction in confirmed measles cases from 1996 to 1999, despite a 1997 resurgence primarily in Brazil.
- Reported cases decreased from 2109 in 1996 to 2828 in 1999, indicating progress towards eradication.
Conclusions:
- PAHO's measles eradication strategy has been effective in interrupting measles transmission.
- Demonstrated that full implementation of vaccination strategies can effectively halt measles transmission.
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