Secondary transmission of SARS-CoV-2 during the first two waves in Japan: Demographic characteristics and overdispersion

Ko, Yura K.; Furuse, Yuki; Ninomiya, Kota; Otani, Kanako; Akaba, Hiroki; Miyahara, Reiko; Imamura, Tadatsugu; Imamura, Takeaki; Cook, Alex R.; Saito, Mayuko; Suzuki, Motoi; Oshitani, Hitoshi

doi:10.1016/j.ijid.2022.01.036

Cited by 15 publications

(21 citation statements)

References 48 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…We found that the early epidemics in Japan exhibited a significant superspreading potential ( k = 0.22), which is in line with another study conducted during a similar study period ( k = 0.23) [ 15 ], but is smaller than an estimate obtained in Hong Kong ( k = 0.43) [ 16 ]. This discrepancy could be attributed to the differences in imposed control policies.…”

Section: Discussionsupporting

confidence: 91%

Differences in the superspreading potentials of COVID-19 across contact settings

Zhao

Guo

et al. 2022

BMC Infect Dis

View full text Add to dashboard Cite

Background Superspreading events (SSEs) played a critical role in fueling the COVID-19 outbreaks. Although it is well-known that COVID-19 epidemics exhibited substantial superspreading potential, little is known about the risk of observing SSEs in different contact settings. In this study, we aimed to assess the potential of superspreading in different contact settings in Japan. Method Transmission cluster data from Japan was collected between January and July 2020. Infector-infectee transmission pairs were constructed based on the contact tracing history. We fitted the data to negative binomial models to estimate the effective reproduction number (R) and dispersion parameter (k). Other epidemiological issues relating to the superspreading potential were also calculated. Results The overall estimated R and k are 0.561 (95% CrI: 0.496, 0.640) and 0.221 (95% CrI: 0.186, 0.262), respectively. The transmission in community, healthcare facilities and school manifest relatively higher superspreading potentials, compared to other contact settings. We inferred that 13.14% (95% CrI: 11.55%, 14.87%) of the most infectious cases generated 80% of the total transmission events. The probabilities of observing superspreading events for entire population and community, household, health care facilities, school, workplace contact settings are 1.75% (95% CrI: 1.57%, 1.99%), 0.49% (95% CrI: 0.22%, 1.18%), 0.07% (95% CrI: 0.06%, 0.08%), 0.67% (95% CrI: 0.31%, 1.21%), 0.33% (95% CrI: 0.13%, 0.94%), 0.32% (95% CrI: 0.21%, 0.60%), respectively. Conclusion The different potentials of superspreading in contact settings highlighted the need to continuously monitoring the transmissibility accompanied with the dispersion parameter, to timely identify high risk settings favoring the occurrence of SSEs.

show abstract

Section: Discussionsupporting

confidence: 91%

Differences in the superspreading potentials of COVID-19 across contact settings

Zhao

Guo

et al. 2022

BMC Infect Dis

View full text Add to dashboard Cite

show abstract

“…However, we observed a higher percentage of symptomatic index cases (57.9% vs. 34.8%) in the facilities that had secondary transmissions ( Supplementary Table S1 ). Symptomatic index cases could cause higher secondary attack rates than asymptomatic index cases [ 35 , 36 ]. Cross-facility movement provoked a spread of SARS-CoV-2 beyond one facility, and was observed in 50% of the COVID-19 clusters ( Table 4 ).…”

Section: Discussionmentioning

confidence: 99%

Epidemiology of SARS-CoV-2 infection in nursing facilities and the impact of their clusters in a Japanese core city

Shimizu

Maeda

Sando

et al. 2022

Journal of Infection and Chemotherapy

View full text Add to dashboard Cite

“…Japan has achieved a high rate of SARS-CoV-2 seroprevalence among adults due to vaccinations since April 2021. In particular, most individuals in their 20s–40s, who were considered to play a major role in driving the COVID-19 epidemic (28), had been vaccinated by August 2021. After that, the country experienced an exceptionally low level of disease spread from September to November 2021 (Figure 1).…”

Section: Discussionmentioning

confidence: 99%

Age-stratified seroprevalence of antibodies against SARS-CoV-2 in the pre- and post-vaccination era, February 2020–March 2022, Japan

Yamayoshi

Iwatsuki‐Horimoto

Okuda

et al. 2022

Preprint

Self Cite

View full text Add to dashboard Cite

Japan has reported a small number of COVID-19 cases relative to other countries. Because not all infected people receive diagnostic tests for COVID-19, the reported number of COVID-19 cases must be lower than the actual number of infections. Assessments of the presence of antibodies against the spike protein of SARS-CoV-2 can retrospectively determine the history of natural infection and vaccination. In this study, we assessed SARS-CoV-2 seroprevalence by analyzing over 60,000 samples collected in Japan from February 2020 to March 2022. The results showed that about 5% of the Japanese population had been infected with the virus by January 2021. The seroprevalence increased with the administration of vaccinations to adults; however, among the elderly, it was not as high as the vaccination rate, probably due to poor immune responses to the vaccines and waning immunity. The infection was spread during the epidemic waves caused by the SARS-CoV-2 Delta and Omicron variants among children who were not eligible for vaccination. Nevertheless, their seroprevalence was as low as 10% as of March 2022. Our study underscores the low incidence of SARS-CoV-2 infection in Japan and the effects of vaccination on immunity at the population level.

show abstract

Secondary transmission of SARS-CoV-2 during the first two waves in Japan: Demographic characteristics and overdispersion

Cited by 15 publications

References 48 publications

Differences in the superspreading potentials of COVID-19 across contact settings

Differences in the superspreading potentials of COVID-19 across contact settings

Epidemiology of SARS-CoV-2 infection in nursing facilities and the impact of their clusters in a Japanese core city

Age-stratified seroprevalence of antibodies against SARS-CoV-2 in the pre- and post-vaccination era, February 2020–March 2022, Japan

Contact Info

Product

Resources

About