Objective  To discuss the epidemiological characteristics of young and middle-aged people infected with COVID-19 in Gansu province under the new epidemic policy. Methods  A total of 1800 people were collected from two tertiary hospitals in Gansu province from November 8, 2022 to January 28, 2023. The vaccination status, nucleic acid antigen detection, the specific time of infection, main symptoms and severity of the disease were investigated. Results  Among 1800 participants, 1685 (93.6%) were vaccinated and 1565 (86.9%) were infected with COVID-19. Among the 1565 infected persons, 523 (33.4%) completed both nucleic acid and antigen testing, 382 (24.4%) completed nucleic acid testing, 490 (31.3%) completed antigen testing, 170 (10.9%) received IgG testing. 1490 (95.2%) were slight ill, 75 (4.8%) were critical ill, and 96 (6.1%) were hospitalized, and no one died. In 2022, 92 cases (5.9%) were infected in the first half of November, 141 cases (9.1%) in the second half of November, 630 cases (40.3%) in the first half of December, and 553 cases (35.4%) in the second half of December. 109 cases (7.0%) were infected in the first half of January, 38 cases (2.2%) in the second half of January, and 2 cases (0.1%) in the first half of February of 2023. and no cases in the second half of February. Among the 1565 infected persons, 825 (52.7%) had respiratory symptoms, 293 (18.7%) had gastrointestinal symptoms, 257 (16.4%) had autonomic disorders, 140 (8.9%) had other symptoms such as decreased smell and taste, and 48 (3.3%) had no symptoms after infection. Conclusions  The vaccination rate of young and middle-aged people in Lanzhou city of Gansu Province is high. Since the new policy, the infection rate of the novel coronavirus among young and middle-aged people is high, the number of antigen tests is more than nucleic acid tests, most of the infected patients are slight, with fewer critical patients, and the hospitalization rate is low. The peak of infection occurred in early December 2022, and the infection rate was basically zero by February 2023. The main symptoms of COVID-19 infection are mainly respiratory tract, followed by digestive tract and autonomic nervous system disorders, and few patients are completely asymptomatic.

Citation： ZHANG Rui, YAN Zhongsheng, NIU Xiaojuan. Epidemiological investigation of COVID-19 infection among young and middle-aged people in Lanzhou City of Gansu province under the new control policy. Chinese Journal of Respiratory and Critical Care Medicine, 2023, 22(7): 480-485. doi: 10.7507/1671-6205.202305035 Copy