International measles incidence and immunization coverage.

Area of Science:

• Epidemiology
• Public Health
• Vaccinology

Background:

• Measles remains a significant global health concern, despite the availability of effective vaccines.
• Immunization programs are critical for controlling measles, with strategies evolving to include multiple vaccine doses and supplementary activities.

Purpose of the Study:

• To quantify the impact of measles-containing vaccine (MCV) doses and supplementary immunization activities (SIAs) on measles incidence.
• To model the relationship between vaccination coverage levels and measles disease reduction.

Main Methods:

• Utilized World Health Organization data on measles incidence and vaccination coverage.
• Employed a negative binomial regression model to analyze the effects of MCV first dose (MCV1), second dose (MCV2), and SIAs.
• Assessed changes in measles incidence relative to varying coverage rates and the implementation of SIAs.

Main Results:

• Measles incidence dramatically decreased from a median of 70.9 cases/100,000/year (0%-39% MCV1 coverage) to 0.9 cases/100,000/year (90%-100% MCV1 coverage).
• Each 1% increase in MCV1 coverage correlated with a 2.0% decrease in incidence; a 1% rise in MCV2 coverage yielded a 0.4% decrease.
• SIAs demonstrated significant effectiveness, reducing measles incidence by over 40% in the same and following years, and herd immunity was observed with MCV1 coverage exceeding 80%.

Conclusions:

• Both single and multiple doses of MCV, alongside SIAs, are highly effective in reducing measles incidence.
• Supplementary immunization activities represent an exceptionally powerful strategy for measles control and elimination efforts.
• High vaccination coverage, particularly for the first dose, is crucial for achieving substantial reductions in measles cases and establishing herd immunity.