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Risk Factors for Measles Virus Infection Among Adults During a Large Outbreak in Postelimination Era in Mongolia,
José E Hagan1, Yoshihiro Takashima2, Amarzaya Sarankhuu3
1Global Immunization Division.
Background:
In 2015, a large nationwide measles outbreak occurred in Mongolia, with very high incidence in the capital city of Ulaanbaatar and among young adults.
Methods:
We conducted an outbreak investigation including a matched case-control study of risk factors for laboratory-confirmed measles among young adults living in Ulaanbaatar. Young adults with laboratory-confirmed measles, living in the capital city of Ulaanbaatar, were matched with 2-3 neighborhood controls. Conditional logistic regression was used to estimate adjusted matched odds ratios (aMORs) for risk factors, with 95% confidence intervals.
Results:
During March 1-September 30, 2015, 20 077 suspected measles cases were reported; 14 010 cases were confirmed. Independent risk factors for measles included being unvaccinated (adjusted matched odds ratio [aMOR] 2.0, P < .01), being a high school graduate without college education (aMOR 2.6, P < .01), remaining in Ulaanbaatar during the outbreak (aMOR 2.5, P < .01), exposure to an inpatient healthcare facility (aMOR 4.5 P < .01), and being born outside of Ulaanbaatar (aMOR 1.8, P = .02).
Conclusions:
This large, nationwide outbreak shortly after verification of elimination had high incidence among young adults, particularly those born outside the national capital. In addition, findings indicated that nosocomial transmission within health facilities helped amplify the outbreak.
Insights
Unvaccinated young adults, those without higher education, and individuals exposed in healthcare facilities were at higher risk during Mongolia's 2015 measles outbreak. Nosocomial transmission amplified the epidemic, especially among those born outside the capital.
Area of Science:
- Epidemiology
- Public Health
- Infectious Disease Surveillance
Background:
- A significant nationwide measles outbreak occurred in Mongolia in 2015.
- The capital city, Ulaanbaatar, and young adults experienced particularly high incidence rates.
Observation:
- A matched case-control study investigated risk factors for measles among young adults in Ulaanbaatar.
- Data included 14,010 confirmed measles cases and neighborhood controls.
Findings:
- Key risk factors identified were unvaccinated status (aMOR 2.0), high school graduation without college (aMOR 2.6), remaining in Ulaanbaatar during the outbreak (aMOR 2.5), healthcare facility exposure (aMOR 4.5), and being born outside Ulaanbaatar (aMOR 1.8).
- Nosocomial transmission within healthcare facilities significantly contributed to outbreak amplification.
Implications:
- The study highlights the vulnerability of young adults to measles, even after elimination verification.
- Findings underscore the importance of vaccination and infection control in healthcare settings to prevent future outbreaks.
- Targeted interventions for young adults, especially those from outside the capital, are crucial for measles control.