Measles immunity gaps and the progress towards elimination: a multi-country modelling analysis

Area of Science:

• Epidemiology
• Immunology
• Public Health

Background:

• Persistent measles circulation necessitates understanding immunity gaps in diverse socioeconomic settings.
• Serological surveys offer direct but often fragmented population immunity estimates.
• This study examines measles immunity changes due to demographics and vaccination policies.

Purpose of the Study:

• To investigate temporal changes in measles immunity across socioeconomic settings.
• To identify current measles immunity gaps and residual susceptibility.
• To inform future measles vaccination strategies.

Main Methods:

• Developed a multi-country measles transmission model for 65 years.
• Calibrated the model using historical serological data.
• Estimated disease burden reduction and age-specific susceptibility.

Main Results:

• Residual measles susceptibility varies from 3% (UK) to over 10% (Kenya, Ethiopia).
• High-income countries show susceptibility concentrated in children under 5.
• Low-income countries have younger susceptible populations, with Supplementary Immunization Activities (SIAs) crucial.

Conclusions:

• High-fertility countries need improved childhood immunization and regular SIAs.
• Low-fertility countries require vaccination campaigns targeting adolescents and adults.
• Tailored strategies are essential to close immunity gaps and control measles.