Background: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which causes coronavirus disease 2019 (COVID-19), has emerged as a serious threat to human health worldwide. Efficient disinfection of surfaces contaminated with SARS-CoV-2 may help prevent its spread. This study aimed to investigate the in vitro efficacy of 222-nm far-ultraviolet light (UVC) on the disinfection of SARS-CoV-2 surface contamination. Methods: We investigated the titer of SARS-CoV-2 after UV irradiation (0.1 mW/cm 2) at 222 nm for 10-300 seconds using the 50% tissue culture infectious dose (TCID 50). In addition, we used quantitative reverse transcription polymerase chain reaction to quantify SARS-CoV-2 RNA under the same conditions. Results: One and 3 mJ/cm 2 of 222-nm UVC irradiation (0.1 mW/cm 2 for 10 and 30 seconds) resulted in 88.5 and 99.7% reduction of viable SARS-CoV-2 based on the TCID 50 assay, respectively. In contrast, the copy number of SARS-CoV-2 RNA did not change after UVC irradiation even after a 5-minute irradiation. Conclusions: This study shows the efficacy of 222-nm UVC irradiation against SARS-CoV-2 contamination in an in vitro experiment. Further evaluation of the safety and efficacy of 222-nm UVC irradiation in reducing the contamination of real-world surfaces and the potential transmission of SARS-CoV-2 is needed.

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Introduction The BNT162b2 and mRNA-1273 COVID-19 vaccines are the main vaccines that have been used for mass vaccination in Japan. Information on adverse reactions to COVID-19 vaccines in the Japanese population is limited. Methods We conducted an online survey on self-reported adverse reactions in individuals who had received two doses of the BNT162b2 mRNA or mRNA-1273 vaccine. The incidence of adverse events after each dose of vaccine was investigated. Propensity score matching was used to compare the incidence of adverse reactions after the second dose of the BNT162b2 mRNA and mRNA-1273 vaccines. Results After the first and second doses of the BNT162b2 vaccine, and the first and second doses of the mRNA-1273 vaccine, 890, 853, 6401, and 3965 individuals, respectively, provided complete responses. Systemic reactions, including fever, fatigue, headache, muscle/joint pain, and nausea were significantly more common in females, individuals aged <50 years, and after the second dose. The incidence of injection site pain did not differ significantly according to the dose. The incidence of delayed injection site reactions after the first dose of mRNA-1273 vaccine was 3.9% and 0.8% among females and males, respectively, and 10.6% among females aged 30–69 years. Local and systemic reactions after the second dose, including fever, fatigue, headache, muscle/joint pain, nausea, and skin rash were more common in individuals who had received the mRNA-1273 vaccine. Conclusions Adverse reactions were more frequently reported in females, younger individuals, and after the mRNA-1273 vaccine.

SARS-CoV-2, the pathogen that causes COVID-19, originated from around Wuhan in China and has spread worldwide, causing a pandemic (WHO, 2020) . People's lives have changed dramatically due to the incorporation of measures for infection prevention. Together with the use of masks for preventing droplet infection, hand washing and hand disinfection for prevention of contact infection have become a part of daily life. Alcohol, especially diethyl alcohol, is used for hand disinfection. An ethanol content of 62-71% was reported in a review article to be effective against SARS-CoV, which is very closely related to SARS-CoV-2 (Kampf et al., 2020) . The included formulations of hand rinses were shown to be effective against SARS-CoV-2 (Kratzel et al., 2020;Suchomel et al., 2020) . On the other hand, Kratzel et al. (2020) examined ethanol concentrations and showed that ethanol at a lower concentration of 30% (v/ v) was effective against SARS-CoV-2 in the presence of 0.03% bovine serum albumin. Ethanol was also found to be effective and fast-acting in a 30-second treatment (Kratzel et al., 2020) .We examined ethanol concentrations that showed an inhibitory effect on SARS-CoV-2 to determine whether the virus can be inactivated at low ethanol concentrations. Effects of ethanol on other envelope viruses, including influenza virus, rhabdovirus and paramyxovirus, were also studied.The 2019-nCoV/Japan/AI/I-004/2020 strain of SARS-CoV-2 (provided by Dr. Makoto Takeda, the National Institute of Infectious Diseases, Japan) was propagated in VeroE6/TMPRSS2 cells (purchased from the Japanese Collection of Research Bioresources; JCRB1819) in the P3 facility of Hiroshima University. Antiviral activity measurement was based on ATSM E1052-11 as previously described (Ueda et al., 2013) . The virus (10 µl) and an ethanol solution (90 µl) were mixed. After reaction for 3 min at room temperature, infectious titers were measured by the standard TCID 50 method using the Behrens-Kraber algorithm (Karber, 1931) . Ethanol was prepared ＊