| Summary: | Background: Despite Malaysia’s long-standing measles elimination
programme and good vaccination coverage, Kelantan has recorded recurrent
outbreaks, calling into question the adequacy of local population immunity and
the role of vaccination to contracting measles risk in Kelantan population.
Objective: To describe the distribution of confirmed measles infection,
to examine the state and specific incidence rate trends of confirmed measles
infection, and to describe the relationship between vaccination status and
confirmed measles infection in Kelantan from 2016 to 2023.
Methods: A cross-sectional study of surveillance data from the SM2 eMeasles system was undertaken. All 5495 suspected cases notified from
January 2016 to December 2023 were analysed. Incidence rates were
calculated with Department of Statistics mid-year population denominators
and presented by year, district, sex, age and ethnicity. Multivariable logistic
regression examined the relationship between vaccination status and
confirmed infection, adjusting for age, sex, ethnicity and contact history.
Results: Only 398 notifications (7.2%) were laboratory-confirmed.
Annual incidence fell from 21.1 per million (2016) to 17.5 (2017), rose sharply to
xxi
69.0 (2019) driven by an Orang Asli outbreak in Gua, declined to zero in 2021
during COVID-19 restrictions, and rebounded to 28.5 in 2023, with Pasir Puteh
emerging as a new hotspot (11.3 / 100 000). Infants less than 1 year persistently
recorded the highest incidence, peaking at 127.4 / 100 000 in 2020. Although
the Orang Asli ethnic constitute only a small proportion of all notifications,
more than half of the Orang Asli cases investigated (56.4%) were confirmed
measles, compared with 6.0% among Malays and 2.1% in other ethnic groups.
After adjustment with each covariate, incomplete vaccination (AOR 3.97, 95%
CI: 2.69, 5.97) and unvaccinated (AOR 3.51, 95% CI 2.39, 5.27) remained strong
predictors of confirmed measles infection compared to complete vaccination.
Contact with a measles positive case (AOR 14.80, 95%CI: 9.36, 23.40) and
Orang Asli ethnicity (AOR 15.4, 95%CI: 10.5, 22.6) were the other major
independent risk factors.
Conclusions: This epidemiological analysis of confirmed measles cases
in Kelantan from 2016 to 2023 highlights that, despite high national vaccination
coverage, significant immunity gaps remain, especially among unvaccinated or
partially vaccinated individuals and within marginalized communities such as
the Orang Asli. The findings highlighted the crucial role of complete vaccination
in reducing confirmed measles infection risk and the need for targeted
immunization drives, culturally tailored outreach, and enhanced surveillance
efforts to prevent future outbreaks and achieve sustained elimination of
measles in the state.
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