Large-scale cross-sectional seroepidemiologic study of COVID-19 in Japan: Acquisition of herd immunity and the vaccines' efficacy

Background: The COVID-19 pandemic situation has been changing drastically worldwide due to the continuous appearance of SARS-CoV-2 variants and the roll-out of mass vaccination. Periodic cross-sectional studies during the surge of COVID-19 cases is essential to elucidate the pandemic situation. Methods: Sera of 1,000 individuals who underwent a health check-up in Hyogo Prefecture Health Promotion Association clinics in Japan were collected in August and December 2021. Antibodies against SARS-CoV-2 N and S antigens were detected in the sera by an electrochemiluminescence immunoassay (ECLIA) and an enzyme-linked immunosorbent assay (ELISA), respectively. The sera's neutralization activities for the conventional SARS-CoV-2 (D614G), Delta, and Omicron variants were measured. Results: The seropositive rates for the antibody against N antigen were 2.1% and 3.9% in August and December 2021 respectively, demonstrating a Delta variant endemic during that time; the actual infection rate was approximately twofold higher than the rate estimated based on the polymerase chain reaction (PCR)-based diagnosis. The anti-S seropositive rate was 38.7% in August and it reached 90.8% in December, in concordance with the vaccination rate in Japan. In the December cohort, 78.7% of the sera showed neutralizing activity against the Delta variant, whereas that against the Omicron was much lower at 36.6%. Conclusions: These analyses revealed that herd immunity against SARS-CoV-2 including the Delta variant was established in December 2021, leading to convergence of the variants. The low neutralizing activity against the Omicron variant suggests the need for the further promotion of the prompt three-dose vaccination to overcome this variant's imminent 6th wave in Japan.

Large-scale seroepidemiologic surveillance of COVID-19 - Cross-sectional study in Hyogo prefecture of Japan in August, 2021

The situation of the COVID-19 pandemic in Japan is drastically changing in the 2nd year, 2021, due to the appearance of SARS-CoV-2 variants of concern and the roll-out of mass vaccination. In addition to PCR diagnosis, periodic seroepidemiologic surveillance is important to analyze the epidemic situation. In this study, we analyzed the rate of seropositivity for the SARS-CoV-2 N and S antigens in Hyogo prefecture, Japan in August 2021. Sera collected from people who received a health check-up in a clinic of the Hyogo Prefecture Health Promotion Association were subjected to analysis of reactivity to the SARS-CoV-2 N and S antigens by electrochemiluminescence immunoassay (ECLIA) and enzyme-linked immunosorbent assay (ELISA), respectively. For a total 1,000 sera, the positive rates to N and S antigens were 2.1% and 38.7%, respectively. The infectious rate estimated by serological analysis based on the presence of the anti-N antibody was 2.5-fold higher than the value reported based on PCR-based analysis, and it increased five-fold compared to the rate determined by our previous seroepidemiologic study in October, 2020. The anti-S positive rate was almost consistent with the vaccination rate in this area. The observed high anti-S antibody level in the seropositive population may indicate that the mass vaccination in Japan is being performed smoothly at this time point, although the infectious rate has also increased.

Complete Genome Sequence of Geobacter sp. Strain SVR, an Antimonate-Reducing Bacterium Isolated from Antimony-Rich Mine Soil

We report here the complete genome sequence of Geobacter sp. strain SVR, isolated from antimony mine soil in Nakase Mine, Hyogo Prefecture, Japan. SVR strains proliferate using antimonate [Sb(V)] as an electron acceptor, providing insights into the antimony reduction mechanism.

Education for Disaster Risk Reduction in Hyogo to Be Handed Down Through Generations

Twenty-five years have passed since the Hanshin-Awaji earthquake. While Hyogo Prefecture and the city of Kobe have made a strong recovery, they also have a social responsibility to pass on lessons learned from the past to future generations. To retell the past, disasters are also well known for their war stories and peace education programs. Various peace education initiatives have been implemented around the world. While many people can talk about the Hanshin-Awaji Earthquake based on their experiences, an increasing number of people have not experienced the disaster. In addition, the number of schoolteachers who cannot describe the disaster to children are increasing because they were born after the disaster. This paper introduces the Promotion Program of Education for disaster risk reduction implemented by the Kobe City Board of Education and investigates how education for disaster risk reduction has developed in schools. The authors involved and surveyed two elementary schools, one junior high school, and one high school. This survey points out the importance of continuous education for disaster risk reduction, and highlights the importance of dialogue and interaction with people who have not experienced the disaster, so that the story of the disaster can be narrated in their own words.