The impact of multi-level interventions on the second-wave SARS-CoV-2 transmission in China

BACKGROUND: A re-emergence of COVID-19 occurred in the northeast of China in early 2021. Different levels of non-pharmaceutical interventions, from mass testing to city-level lockdown, were implemented to contain the transmission of SARS-CoV-2. Our study is aimed to evaluate the impact of multi-level control measures on the second-wave SARS-CoV-2 transmission in the most affected cities in China. METHODS: Five cities with over 100 reported COVID-19 cases within one month from Dec 2020 to Feb 2021 were included in our analysis. We fitted the exponential growth model to estimate basic reproduction number (R(0)), and used a Bayesian approach to assess the dynamics of the time-varying reproduction number (R(t)). We fitted linear regression lines on R(t) estimates for comparing the decline rates of R(t) across cities, and the slopes were tested by analysis of covariance. The effect of non-pharmaceutical interventions (NPIs) was quantified by relative R(t) reduction and statistically compared by analysis of variance. RESULTS: A total of 2,609 COVID-19 cases were analyzed in this study. We estimated that R(0) all exceeded 1, with the highest value of 3.63 (1.36, 8.53) in Haerbin and the lowest value of 2.45 (1.44, 3.98) in Shijiazhuang. Downward trends of R(t) were found in all cities, and the starting time of R(t) < 1 was around the 12th day of the first local COVID-19 cases. Statistical tests on regression slopes of R(t) and effect of NPIs both showed no significant difference across five cities (P = 0.126 and 0.157). CONCLUSION: Timely implemented NPIs could control the transmission of SARS-CoV-2 with low-intensity measures for places where population immunity has not been established.