Association of COVID-19 vaccine intake with diagnosis, hospitalization, and oxygenation/ventilation: A longitudinal analysis, 2021-2022, Japan (preprint)

Limited national-level data exist on COVID-19 vaccine effectiveness against infection outcomes based on individual characteristics. We analyzed 19,482 individuals aged 16-81 who responded to baseline (2021) and follow-up (2022) Internet-based surveys. COVID-19 vaccine intake (0/1/2+ doses) during the follow-up period was examined, and outcomes included COVID-19 diagnosis, hospitalization, and oxygenation/ventilation. Adjusted prevalence ratios (APRs) were computed using Poisson regression models, controlling for baseline characteristics including precautionary measures practiced. 81.6% of respondents received ≥1 dose of COVID-19 vaccine during the follow-up period. Among those without COVID-19 history at baseline (N=19,182), 10.9% and 6.6% reported COVID-19 diagnosis within the past year and past 2 months at follow-up, respectively. Respondents who received 1 or 2+ doses were less likely to be diagnosed in the past year (APR=0.76 and 0.43) and past 2 months (APR=0.87 [not statistically significant] and 0.51) compared to those who did not. Among 1,999 respondents diagnosed with COVID-19 during the follow-up, those with 1 or 2+ vaccine doses showed lower likelihoods of hospitalization (APR=0.78 and 0.86) and receipt of oxygenation/ventilation (APR=0.87 and 0.61), although not statistically significant. Considering the interaction of socioeconomic and behavioral characteristics, the results supported the protective effect of the COVID-19 vaccine against infection.

Factors Associated with Serious Psychological Distress during the COVID-19 Pandemic in Japan (preprint)

Importance: The coronavirus disease 2019 (COVID-19) pandemic may have a negative impact on mental health, leading to higher suicide rates in many countries. However, little is known about the factors associated with worsened mental health during the COVID-19 pandemic. Objective: To investigate the factors associated with serious psychological distress (SPD) during the COVID-19 pandemic in Japan. Design, Setting, and Participants: A cross-sectional study using a large-scale internet survey conducted between August 25 and September 30, 2020, in Japan. Exposures: Demographics (age, gender, marital status, family composition, and caregiving burden), socio-economic status (income level, employment type, educational attainment); the experience of domestic violence (DV), the state of emergency, fear of COVID-19, and stigma related to COVID-19. Main Outcomes and Measures: Prevalence of SPD, defined as Kessler 6 scale score [≥]13. Results: Among 25,482 individuals included in this study, 2,556 (10%) met the criteria of SPD. Overall, women (adjusted odds ratio [aOR] 1.59; 95%CI, 1.17-2.16; P=0.003), ages 15-29 (aOR compared with ages 45-59, 2.35; 95%CI, 1.64-3.38; P<0.001), low income (aOR compared with intermediate income, 1.70; 95%CI, 1.16-2.49; P=0.007), those who provide caregiving to family members (aOR, 5.48; 95%CI, 3.51-8.56; P<0.001), experiencing DV (aOR, 5.72; 95%CI, 3.81-8.59; P<0.001), and fear of COVID-19 (aOR, 1.96; 95%CI, 1.55-2.48; P<0.001) were associated with a higher prevalence of SPD. Among women aged 15-29 years who experienced the highest rate of SPD, caregiving, DV, fear of COVID-19, and COVID-19-related stigma were associated with a higher likelihood of SPD; whereas economic situation (income level and employment type) and social isolation (marital status) were not associated with the prevalence of SPD. Conclusions and Relevance: Economic situation, caregiving burden, DV, and fear of COVID-19 were independently associated with SPD during the COVID-19 pandemic. Among young women--who have a higher risk of suicide during the COVID-19 pandemic in Japan--similar factors, except economic situation, were associated with a higher rate of SPD. Targeted interventions based on age and gender may be more effective in mitigating the negative impact of the COVID-19 pandemic on the population's mental health.