BackgroundWith the measles vaccine coverage rate gradually increasing, adult patients’ epidemiological and clinical characteristics have changed.AimsTo analyze the clinical characteristics of adult measles patients in Beijing Youan Hospital.MethodsWe retrospectively reviewed the electronic medical records of 818 patients diagnosed with measles at Beijing Youan Hospital between June 2010 and October 2021. We divided all hospitalized patients into two demographics groups, using 14 years of age as the cut-off.ResultsOf the adult inpatients, 110 (74.83%) were aged 20–40. There was an overall peak incidence in 2014, and yearly peaks came in April. Fever, cough, erythema, and Koplik’s spots were present in 79.59%, 82.1%, 99.3%, and 59.8% of the adult group, respectively, compared to 75.26%, 92.0%, 99.9%, and 39.0% of the pediatric group. Decreased lymphocytes and hepatic impairment were common in adults. The adult group’s median level of C-reactive protein was higher than that of the pediatric group (p < 0.05). The positive rate of measles antibody (IgM) detection was 64.6% in the adults and 78.8% in the pediatric group (p < 0.05). Of the adults, 46.9%, 8.8%, and 66% had pneumonia, gastroenteritis, and antibiotic use, compared to 89.6%, 2.7%, and 83.2% of the pediatric patients. The duration of symptoms before admission and the average length of hospital stay was approximately six days in both groups.ConclusionsKoplik’s spots are more likely to be detected by clinicians in adult patients admitted to the hospital. Active surveillance is helpful for adults who are negative for IgM on admission. Although the proportion of adult measles patients with liver injury is high, the disease is generally mild. Measles significantly impacts peripheral blood lymphocytes in adults, but adults are at lower risk of concurrent pneumonia than the pediatric group. Clinicians need to pay attention to the appropriate use of antibiotics. Expanding the coverage of the measles vaccination in high-risk areas is beneficial for preventing measles in adults.