ABSTRACT
Background: Earlier studies have indicated the BA.5 sublineage of Omicron variant strain of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) as more infective than BA.2. Object: This study estimated BA.5 infectivity while controlling other factors possibly affecting BA.5 infectivity including vaccine effectiveness, waning effectiveness, other mutated strains, Olympic Games, and countermeasures. Method: The effective reproduction number R(t) was regressed on shares of BA.5 and vaccine coverage, vaccine coverage with some delay, temperature, humid-ity, mobility, shares of other mutated strains, counter-measures including the Go to Travel Campaign, and the Olympic Games and associated countermeasures. The study period was February 2020–July 22, 2022, using data available on August 12, 2022. Results: A 120 day lag was assumed to assess waning. Mobil-ity, some states of emergency, vaccine coverage and those with lag, and the Delta and Omicron BA.2 pro-portions were found to be significant. The omicron BA.1 proportion was significant, but with an unex-pected sign. The estimated coefficient of BA.5 was negative but not significant. The Go to Travel Campaign was significantly negative, indicating reduced infectiv-ity. The Olympic Games were negative but not sig-nificant, indicating that they did not raise infectivity. Discussion: The obtained estimated results show that BA.5 did not have higher infectivity than the original strain. It was lower than either Delta or Omicron BA.2 variant strains. That finding might be inconsis-tent with results obtained from earlier studies. This study controlled several factors potentially affecting R(t), though the earlier studies did not. Therefore, results from this study might be more reliable than those of earlier studies. © Fuji Technology Press Ltd.
ABSTRACT
Background: Countermeasures against COVID-19 outbreak, such as lockdowns and voluntary restrictions against going out, adversely affect human stress and depress economic activity. Particularly, this stress might lead to suicide. Object: We examined excess mortality attributable to COVID-19 related suicide. Method: We applied the National Institute of Infectious Diseases (NIID) model to suicide deaths, by gender, throughout Japan during October 2009-January 2021. Effects of the great earthquake that struck eastern Japan on March 11, 2011 were incorporated into the estimation model.
ABSTRACT
Background: No remarkable excess mortality attributable to COVID-19 has been observed in Japan until the delta strain of COVID-19 emerged. Object: We sought to quantify high pathogenicity of the delta strain using the National Institute of Infectious Diseases (NIID) model. Method: We applied the NIID model to deaths of all causes from 1987 up through August 2021 for the whole of Japan.
ABSTRACT
Background: No remarkable excess mortality attributable to COVID-19 has been observed in Japan until the delta strain of COVID-19 emerged. Object: We sought to quantify high pathogenicity of the delta strain using the National Institute of Infectious Diseases (NIID) model. Method: We applied the NIID model to deaths of all causes from 1987 up through August 2021 for the whole of Japan. Results: Results in Japan show 4105 excess mortality in August 2021 in Japan. It was estimated as 3.8% of the baseline. Discussion and Conclusion: We found substantial excess mortality since the outbreak of COVID-19 had emerged in August 2021, in Japan. It might be due to spread of delta strain at that time.