Association between Immunization Status and Encephalitis in Pediatric Measles Cases

Abstract

Objective: To examine the association between measles immunization status and encephalitis among hospitalized children aged 1–5 years with measles. Study Design and Setting: Analytical cross-sectional study conducted in the Department of Pediatric Medicine, Allied Hospital, Faisalabad. Methodology: Total 133 children aged 1–5 years with clinically compatible measles were enrolled. Children with chronic systemic disease, immunocompromised status, or hereditary syndromes were excluded. Immunization status was verified from the EPI vaccination card. Measles case classification followed WHO surveillance criteria; measles-specific IgM and/or RT-PCR was used for laboratory confirmation. Encephalitis was defined by sustained altered mental status with supportive neurological features. Pearson chi-square testing was used for the primary 2×2 comparison because expected cell counts were adequate; two-sided Fisher exact testing was reported as a sensitivity analysis. Statistical significance was defined as p<0.05. Results: Mean age was 3.12 ± 1.18 years. Of 133 children, 46 (34.6%) were fully immunized and 87 (65.4%) were unimmunized/incompletely immunized. Encephalitis occurred in 21/133 children (15.8%; 95% CI 10.6%–22.9%): 3/46 fully immunized children (6.5%) and 18/87 un-immunized/incompletely immunized children (20.7%). The crude sample OR was 3.74 with a conditional exact 95% CI of 0.996–20.81; the crude PR/RR was 3.17 (95% CI 0.95–8.32) and the RD was 14.2 percentage points (95% CI 1.0–24.7). Pearson chi-square p=0.033; two-sided Fisher exact p=0.044. Delayed presentation (>7 days) was also associated with encephalitis in unadjusted analysis. Conclusion: Among hospitalized pediatric measles cases, un-immunized/incompletely immunized status was associated with a higher observed frequency of encephalitis than full immunization