We aimed to elucidate the range of the incubation period in patients infected with the SARS-CoV-2 Omicron variant in comparison with the Alpha variant. Contact tracing data from three Japanese public health centers (total residents, 1.06 million) collected following the guidelines of the Infectious Diseases Control Law were reviewed for 1589 PCR-confirmed COVID-19 cases diagnosed in January 2022. We identified 77 eligible symptomatic patients for whom the date and setting of transmission were known, in the absence of any other probable routes of transmission. The observed incubation period was 3.03 ± 1.35 days (mean ± SDM). In the log-normal distribution, 5th, 50th and 95th percentile values were 1.3 days (95% CI: 1.0–1.6), 2.8 days (2.5–3.1) and 5.8 days (4.8–7.5), significantly shorter than among the 51 patients with the Alpha variant diagnosed in April and May in 2021 (4.94 days ± 2.19, 2.1 days (1.5–2.7), 4.5 days (4.0–5.1) and 9.6 days (7.4–13.0), p < 0.001). As this incubation period, mainly of sublineage BA.1, is even shorter than that in the Delta variant, it is thought to partially explain the variant replacement occurring in late 2021 to early 2022 in many countries.

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.

Although both varenicline and nicotine patch have a beneficial effect in controlling postcessation weight gain, it is not well known whether there is a difference in the effect. We conducted a multi-institutional study on smoking cessation therapy (SCT) administered at 4 Japanese hospitals to compare the body weight change from the first session to 12 months after the end of SCT (at 60 weeks) between varenicline users (n = 307) and nicotine patch users (n = 45). The mean weight change from baseline to 12 months after the end of SCT was +0.94kg (SD: 3.59) in varenicline users and +2.78kg (SD: 4.88) in nicotine patch users (p = .003, by t test). In multivariate linear regression analysis, varenicline users gained significantly less weight than nicotine patch users (coefficient: −1.787, 95% CI = −2.98 to −0.59) with adjustment for success of quit smoking, age, sex, presence of comorbidity, body mass index at baseline, Fagerström Test for Nicotine Dependence, craving at the end of SCT, and nausea through the SCT. Our results indicated that varenicline is more effective in attenuating weight gain than nicotine patch in smokers who received Japanese SCT.

Introduction: Despite the effectiveness of smoking cessation counseling, participation of nurses in delivering smoking cessation advice has been far from satisfactory in practice. Training nurses is considered to be important for increasing selfefficacy and skills for routine delivery of...