Clinical characteristics of imported patients infected with 2019 novel coronavirus Omicron variants and Delta variants in Guangzhou City / 中华传染病杂志

ABSTRACT

Objective:To analyze and compare the clinical characteristics and prognosis of imported patients infected with 2019 novel coronavirus (2019-nCoV) Omicron variants and Delta variants, so as to provide references for clinical diagnosis, treatment and epidemic prevention strategies.Methods:The patients with imported 2019-nCoV infection from August 1, 2021 to January 18, 2022 in Guangzhou Eighth People′s Hospital, Guangzhou Medical University were retrospectively analyzed. According to the whole genome sequencing of 2019-nCoV in nasal or throat swabs, they were divided into Omicron group and Delta group. The clinical characteristics, laboratory tests, antibody levels, viral nucleic acid (the cycle threshold (Ct) of N gene and open reading frame ( ORF) 1 ab), main treatment measures and clinical prognosis were analyzed in the two groups. Statistical analysis was performed using the rank sum test, chi-square test or Fisher′s exact test. Results:A total of 344 cases were enrolled, including 152 cases in the Delta group and 192 cases in the Omicron group, and there were 240 males (69.8%), with a median age of 33 years old. One hundred and two (29.7%) of those patients had underlying disease.Two hundred and seventy-one had completed full or booster vaccination. The overall full vaccination rate in Omicron group was 70.8%(136/192), which was higher than 51.3%(78/152) in Delta group. The proportion of mild patients in Omicron group was higher than that in Delta group (57.3%(110/192) vs 24.3%(37/152), respectively), and the proportions of common type and severe type were lower than those of the Delta group (33.9%(65/192) vs 55.3%(84/152) and 0(0/192) vs 10.5%(16/152)), the differences were all statistically significant ( χ2=37.64 and 15.84, respectively, Fisher′s exact test; all P<0.001). The duration and peak of fever in Omicron group were 1.5(1.0, 2.0) d and 38.1(37.8, 38.5) ℃, respectively, which were lower than those in Delta group (3.0(1.0, 4.8) d and 38.5(38.1, 39.0) ℃, respectively), and the differences were both statistically significant ( Z=-4.14 and -3.85, respectively, both P<0.001). The 2019-nCoV antibody IgG and the Ct values of virus nucleic acid N gene and ORF1 ab gene in the vaccinated Omicron group at admission were higher than those in the Delta group ( Z=-3.25, -2.18 and -2.82, respectively, all P<0.050). Compared with patients in Delta group, patients in Omicron group had lower proportion of receiving respiratory therapy support, shorter oxygen therapy time, shorter reversion time from admission to nucleic acid Ct value≥35 and shorter hospitalization time. The differences were all statistically significant ( χ2=47.86, Z=-5.41, -5.60 and -4.71, respectively, all P<0.001). There was no critical illness or 28-day death case in both groups. Conclusions:The severity of patients infected with Omicron variants is lighter than that of patients with Delta variants, and the viral nucleic acid has shorter conversion time, which is mainly related to the virulence of variant strain and vaccination.