Infectivity of omicron BQ.1.1 comparison with other strains of SARS-Cov-2 in Japan

Abstract

Abstract

Background: After decline of BA.5 sublineage of omicron variant strain of SARS-CoV-2, BQ.1.1. sublineage had been emerging.

Object: The object of this study was to estimate infectivity of BQ.1.1. sublineage controlling other factors that might affect BQ.1.1’s infectivity including vaccine effectiveness and waning, the mutated strain other than BQ.1.1, and countermeasuresBQ.1.1.

Method: The effective reproduction number(R(t)) was regressed on shares of BQ.1.1. as well as vaccine coverage, vaccine coverage with some delay, temperature, humidity, mobility, share of the other mutated strains, counter measures including Go To Travel Campaign and an Olympic Games. The study period was February, 2020 through the end of year 2022, as of January 31, 2023.

Results : We selected the specification with 90 days lag of waning. In this specification, Goto Travel Campaign and Olympic games were significantly negative and thus these event reduced infectivity. The estimated coefficient of BQ.1.1 sublineage of omicron variant strain was positive but insignificant.

Discussion: The obtained estimated results showed that BQ.1.1 may not have higher infectivity than BA.1, BA.2, BA.5 or other minor sublineage of omicron variant strains. It might be consistent with slower and gradually replacement from BA.5 to BQ.1.1.