プレプリント / バージョン1

Infectiousness in omicron BA.2 (B.1.1.529.2) an effectiveness of the fourth vaccination BA.2 in Japan


  • Kurita, Junko Department of Nursing, Faculty of Sports & Health Science ,Daitoubunka University
  • Tamie Sugawara Infectious Disease Surveillance Center, National Institute of Infectious Diseases
  • Yasushi Ohkusa Infectious Disease Surveillance Center, National Institute of Infectious Diseases




COVID-19、 effective reproduction number、 omicron、 vaccine coverage、 vaccine effectiveness、 BA.2


Background: Omicron variant strain dominated since the beginning of 2022. Its infectivity was supposes to be higher than Delta variant strain or strains in past. Moreover, the fourthe vaccination had started in May, 2022.

Object: We estimated prevalence of omicron variant strain, particularly BA.2 (B.1.1.529.2) variant and COVID-19 vaccine effectiveness of the third dose in Japan as well as controlling for waning of second dose of vaccine, other mutated strains, the Olympic Games, and countermeasures.

Method: The effective reproduction number R(t) was regressed on shares of omicron variant strain and BA.2 and vaccine coverage of the third dose, as well as along with data of temperature, humidity, mobility, share of the other mutated strains, and an Olympic Games and countermeasures. The study period was February, 2020 through February 21, 2022, as of March 15, 2022.

Results : Estimation results indicated that waning of the second dose vaccine e with 150 days prior was the most appropriate specification.  Moreover, BA.2 of omicron variant strain has higher infectively than other variant strain or traditional strain.

Discussion: Because of data limitation since emerging BA.2, the estimated its infectively will change over time.

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投稿日時: 2022-07-25 05:01:51 UTC

公開日時: 2022-07-26 09:28:56 UTC