CLINICAL FEATURES OF MEASLES IN VACCINATED AND UNVACCINATED CHILDREN: DIFFERENTIAL DIAGNOSIS FROM COXSACKIE VIRUS INFECTION, RUBELLA, AND SCARLET FEVER, ALONG WITH INTERESTING LABORATORY FINDINGS

Abstract

Measles, a highly contagious acute viral illness caused by the measles virus (a single-stranded RNA paramyxovirus), remains a significant global health concern despite the availability of an effective vaccine. It presents with a characteristic prodrome of the “three Cs” (cough, coryza, conjunctivitis) plus high fever, followed by pathognomonic Koplik spots and a centrifugal maculopapular rash. In unvaccinated children, the disease is typically severe, with complications such as pneumonia (1–6 per 100 cases), encephalitis, diarrhea, and otitis media occurring in up to 30% of cases; global estimates indicate approximately 10.3 million infections and 95,000 deaths in recent years, predominantly among unvaccinated children under 5 years. In vaccinated children (one or two doses of MMR), breakthrough infections are milder or “modified,” with reduced fever intensity, absent or atypical Koplik spots, less pronounced rash, and markedly lower hospitalization and complication rates (e.g., vaccinated cases show statistically fewer severe symptoms and complications compared with unvaccinated, p<0.05 in multiple pediatric cohorts).