Measles in Selangor: A Comparative Analysis Between Adults and Children Using the E-Measles Registry, 2015-2024

Measles remains a persistent public health concern in Malaysia. Despite sustained high vaccination coverage in states such as Selangor, reported cases continue to increase. This trend suggests a possible shifting age-distribution of measles, a pattern that has been observed in countries with a high vaccination rate. Understanding the epidemiology and clinical characteristics of measles between adults and children is critical in guiding targeted public health interventions aimed at control and elimination of measles. This study aimed to describe the incidence of measles in adults and children in Selangor, and to compare their sociodemographic, clinical, vaccine, and exposure-related differences.

This comparative cross-sectional study used secondary data from the Selangor e-Measles Registry from 2015 to 2024. Confirmed cases were classified as adults (≥18 years) and children (<18 years). The incidence of each group was calculated annually over ten years. Descriptive statistics, chi-square test, Fisher's exact test, and Mann-Whitney U test were used to describe and compare the differences between the two groups. Data were analysed using SPSS version 29.

A total of 3954 confirmed measles cases were included in the study, with 540 (13.7%) adult cases and 3414 (86.3%) cases in children. Between 2015 and 2024, the incidence of measles was consistently higher in children as compared to adults, with risk ratios ranging from 14.43 (95% CI: 11.25, 18.73) in 2017 to 87.65 (95% CI: 27.39, 278.66) in 2022. With the exception of 2019-2022, adults showed a gradual increase in number over the study period, with the highest proportion in 2023 (16.4%). Significant differences between adults and children were observed (p<0.05) according to nationality, ethnicity, clinical symptoms, hospitalisation, complications, vaccination status, and duration since the last vaccination.

The findings suggest that despite the increase in adult cases, measles predominantly affects children in Selangor. The findings highlight the need to strengthen vaccination efforts through the National Immunisation Programme (NIP) and prioritising Supplementary Immunisation Activities (SIAs) among children aged below 6 years old. Additionally, the gradual rise in cases in adults and children aged 7-12 years old should be monitored closely to detect emerging epidemiological shifts. Significant clinical differences between adults and children highlight the need for training of healthcare providers and public education to support diagnosis, prevent outbreaks, and avoid complications. Digitalisation of health records, such as the documentation of vaccination history, is needed.

Measles in Selangor showed age-specific trends and differences. Addressing these issues through strengthened childhood immunisation, targeted interventions and continuous surveillance is essential to achieve measles control and elimination in Selangor and Malaysia.