SFTS has been endemic to Japan, and SFTSV has been circulating naturally within the country.

Objective: To identify common features of cases with novel coronavirus disease (COVID-19) so as to better understand what factors promote secondary transmission including superspreading events. Methods: A total of 110 cases were examined among eleven clusters and sporadic cases, and investigated who acquired infection from whom. The clusters included four in Tokyo and one each in Aichi, Fukuoka, Hokkaido, Ishikawa, Kanagawa and Wakayama prefectures. The number of secondary cases generated by each primary case was calculated using contact tracing data. Results: Of the 110 cases examined, 27 (24.6%) were primary cases who generated secondary cases. The odds that a primary case transmitted COVID-19 in a closed environment was 18.7 times greater compared to an open-air environment (95% confidence interval [CI]: 6.0, 57.9). Conclusions: It is plausible that closed environments contribute to secondary transmission of COVID-19 and promote superspreading events. Our findings are also consistent with the declining incidence of COVID-19 cases in China, as gathering in closed environments was prohibited in the wake of the rapid spread of the disease.

A c c e p t e d M a n u s c r i p t

HE THREAT OF SMALLPOX BIOterrorism has prompted reconsideration of the need for smallpox vaccination. 1-3 Serious adverse events associated with firstgeneration vaccines such as the New York City Board of Health (Dryvax; Wyeth, Madison, New Jersey), Lister, and Ikeda strains 4-8 have raised obstacles to vaccination campaigns in the United States. 7-9 Second-generation vaccines such as ACAM2000 (Acambis, Cambridge, Massachusetts) that use a first-generation seed virus but are grown in tissue culture are also usually accompanied by a high frequency of adverse events. 10 Developing a vaccine that is safer than first-generation vaccines yet highly immunogenic is crucial to constructing a prevention plan in the event of bioterrorist attack. LC16m8 is a live, attenuated, tissuecultured third-generation vaccine comprising attenuated vaccinia virus strains as well as subunit vaccines made from viral proteins or DNA. 11 It is a desirable candidate for routine vaccination because of its low reactogenicity and reasonable safety profile. 12 Vaccination can be conveniently accomplished with a single intraepidermal scarification alone, which usually results in a visible major skin reaction ("take") similar to those resulting from first-and second-generation vaccines. 13 LC16m8 was derived from the Lister strain used for the Intensified Smallpox Eradication Programme of the World Health Organization 4 by temperature sensitivity and pock size See also Patient Page.