Outcome of Measles in Vaccinated versus Unvaccinated Children under 5 years of age

Abstract

Objective: To determine the frequency of measles vaccination among children under 5 years of age presenting with measles and to compare the outcomes between vaccinated and unvaccinated children. Outcomes were defined as (i) prolonged hospital admission of two days or more (primary outcome, taken as the marker of severe disease) and (ii) measles-related complications (secondary outcome).

Methods: This descriptive cross-sectional study was conducted at the Department of Paediatrics, Benazir Bhutto Hospital, Rawalpindi, from October 2025 to December 2025, and reported in accordance with the STROBE guidelines for cross-sectional studies. A total of 150 children aged 1–5 years of either sex were enrolled using non-probability consecutive sampling. Measles was defined by the WHO clinical case definition (fever ≥38 °C with a generalised maculopapular rash lasting ≥3 days, together with at least one of cough, coryza, or conjunctivitis). A child was classified as vaccinated when at least one dose of a measles-containing vaccine given at or after 9 months of age was documented on the Expanded Program on Immunisation (EPI) card, and as unvaccinated when no dose was documented. Children with chickenpox, other skin infections, congenital anomalies, chronic illnesses, immunocompromised status, or incomplete vaccination records were excluded. Groups were compared using the chi-square test, and effect sizes were reported as odds ratios (OR), risk ratios (RR), and absolute risk differences with 95% confidence intervals (CI).

Results: The mean age of the children was 3.18 ± 1.21 years, and the mean weight was 12.46 ± 2.84 kg. Of the 150 children, 38 (25.3%) were vaccinated, and 112 (74.7%) were unvaccinated. Prolonged hospital admission was required by 57 of 112 (50.9%) unvaccinated children compared with 10 of 38 (26.3%) vaccinated children (OR 2.90, 95% CI 1.29–6.53; RR 1.93, 95% CI 1.10–3.39; absolute risk difference 24.6%, 95% CI 7.8–41.4; p = 0.009). Complications were observed in 73 (48.7%) children overall, with pneumonia being the most common complication in 34 (22.7%), followed by diarrhoea in 21 (14.0%), otitis media in 10 (6.7%), and encephalitis in 8 (5.3%). The overall frequency of complications did not differ significantly between unvaccinated (55/112, 49.1%) and vaccinated (18/38, 47.4%) children (OR 1.07, 95% CI 0.51–2.24; p = 0.853).

Conclusion: Unvaccinated children < 5 years of age with measles had a significantly greater need for prolonged hospital admission than vaccinated children, indicating that measles vaccination attenuates the severity of illness in children who acquire the infection. The overall frequency of complications did not differ significantly between the two groups; this null result should be interpreted cautiously, given the small number of vaccinated children and the correspondingly wide confidence interval. These findings support the need to strengthen routine measles immunisation coverage in children under 5 years of age.

Keywords: Measles; Measles Vaccine; Vaccination; Child, Preschool; Hospitalization; Treatment Outcome; Immunization Programs; Pakistan.