Increased Transmissibility of the SARS-CoV-2 Alpha Variant in a Japanese Population

Hideo Tanaka, Atsushi Hirayama, Hitomi Nagai, Chika Shirai, Yuki Takahashi, Hiroto Shinomiya, Chie Taniguchi and Tsuyoshi Ogata
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Hideo Tanaka: Fujiidera Public Health Center of Osaka Prefectural Government, Fujiidera 583-0024, Japan
Atsushi Hirayama: Department of Public Health and Medical Affairs, Osaka Prefectural Government, Osaka 540-8507, Japan
Hitomi Nagai: Ibaraki Public Health Center of Osaka Prefectural Government, Ibaraki 567-8585, Japan
Chika Shirai: Hirakata City of Public Health Center, Hirakata 573-8666, Japan
Yuki Takahashi: Fujiidera Public Health Center of Osaka Prefectural Government, Fujiidera 583-0024, Japan
Hiroto Shinomiya: Ehime Prefectural Institute of Public Health and Environmental Science, Matsuyama 790-0003, Japan
Chie Taniguchi: College of Nursing, Aichi Medical University, Nagakute 480-1195, Japan
Tsuyoshi Ogata: Itako Public Health Center of Ibaraki Prefectural Government, Itako 311-2422, Japan

IJERPH, 2021, vol. 18, issue 15, 1-6

Abstract: To assess the relative transmissibility of the SARS-CoV-2 Alpha variant compared to the pre-existing SARS-CoV-2 in Japan, we performed a cross-sectional study to determine the secondary attack rate of COVID-19 in household contacts before and after the Alpha variant became dominant in Osaka. We accessed 290 household contacts whose index cases were diagnosed between 1 and 20 December 2020 (the third epidemic group), at a time when Osaka was free of the Alpha variant. We also accessed 398 household contacts whose index cases were diagnosed between 20 April and 3 May 2021 (the fourth epidemic group), by which time the Alpha variant had become dominant. We identified 124 household contacts whose index case was determined positive for the Alpha variant (Alpha group) in this fourth group. The secondary attack rates in the fourth group (34.7%) and the Alpha group (38.7%) were significantly higher than that in the third group (19.3%, p < 0.001). Multivariable Poisson regression analysis with a robust error variance showed a significant excess risk in the fourth group (1.90, 95% CI = 1.47–2.48) and the Alpha group (2.34, 95% CI = 1.71–3.21). This finding indicates that the SARS-CoV-2 Alpha variant has an approximately 1.9–2.3-fold higher transmissibility than the pre-existing virus in the Japanese population.

Keywords: SARS-CoV-2; Alpha variant; N501Y; transmissibility; household contact; Japanese (search for similar items in EconPapers)
JEL-codes: I I1 I3 Q Q5 (search for similar items in EconPapers)
Date: 2021
References: View complete reference list from CitEc
Citations: View citations in EconPapers (2)

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