BF.7: a new Omicron subvariant characterized by rapid transmission

Abstract

Objectives: BF.7 (BA.5.2.1.7) is a novel sublineage of Omicron BA.5, whose clinical characteristics are not yet established.

Methods: From 28 September 2022 to 3 October 2022, the first 421 patients with BF.7 were assessed in Hohhot China and the clinical data were extracted and analysed. The basic reproduction number (R0) was estimated using a statistical model calculation method.

Results: The R0 value was determined to be 13.79 (95% confidence interval: 12.44-15.24). The mean age was 33.43 ± 18.78 years. Asymptomatic, mild, moderate, severe, and critical patients accounted for 12.35% (52/421), 82.42% (347/421), 4.75% (20/421), 0.24% (1/421), and 0.24% (1/421) proportion, respectively. The main clinical symptoms were fever accounting for 41.09% (173/421), cough accounting for 41.09% (173/421), and throat dryness and soreness accounting for 30.88% (130/421). In the 3-dose vaccination subgroup, 31.22% (64) cases had a fever, which were significantly lower than 51.37% (96) cases of the 2-dose vaccination subgroup (p 0.000). The rates of abnormally increased C-reactive protein level in the 2-dose and 3-dose vaccination subgroups were 10.16% (19/187) and 4.88% (10/205), significantly lower than 66.67% (10/15) of the 1-dose vaccination subgroup (1-dose vs. 2-dose: p 0.000, 1-dose vs. 3-dose: p 0.000). Notably, the population with complete 3 doses of vaccination did not exhibit any severe or critical status.

Discussion: BF.7 exhibited a higher transmission than previously emerged SARS-CoV-2. The vaccine against COVID-19 was found to relieve fever, nausea, and vomiting as well as reduce the abnormal ratio of lymphocytes, eosinophils, neutrophils, and the C-reactive protein level.

Keywords: BF.7; Clinical characteristics; Coronavirus disease 2019; Omicron; Vaccine effectiveness.