Association between COVID-19 infection rates by region and implementation of non-pharmaceutical interventions: A cross-sectional study in Japan (preprint)

ABSTRACT

Background: During a pandemic, non-pharmaceutical interventions (NPIs) play an important role in protecting oneself from infection and preventing the spread of infection to others. There are large regional differences in COVID-19 infection rates in Japan. We hypothesized that the local infection incidence may affect adherence to individual NPIs. Methods: This cross-sectional study was conducted online among full-time workers in Japan in December 2020. Data from a total of 27,036 participants were analyzed. The questionnaire asked the respondents to identify their habits regarding seven well-known NPIs. Results: Compared to the region with the lowest infection rate, the odds ratios for the region with the highest infection rate were 1.24 (p<0.001) for wearing a mask in public, 1.08 (p=0.157) for washing hands after using the bathroom, 1.17 (p=0.031) for disinfecting hands with alcohol sanitizers when entering indoors, 1.54 (p<0.001) for gargling when returning home, 1.45 (p<0.001) for ventilating the room, 1.33 (p<0.001) for disinfecting or washing hands after touching frequently touched surfaces, and 1.32 (p<0.001) for carrying alcohol sanitizers when outdoors. Five of the seven NPIs showed statistically significant trends across regional infection levels, the two exceptions being wearing a mask in public and washing hands after using the bathroom. Multivariate adjustment did not change these trends. Conclusions: This study found that NPIs were more prevalent in regions with higher incidence rates of COVID-19 in Japanese workers. The findings suggest that the implementation of NPIs was influenced not only by personal attributes but also by contextual effects of the local infection level.