  The pandemic of COVID-19 has caused severe public health consequences around
the world. Many interventions of COVID-19 have been implemented. It is of great
public health and societal importance to evaluate the effects of interventions
in the pandemic of COVID-19. In this paper, with help of synthetic control
method, regression discontinuity and a Susceptible-Infected and infectious
without isolation-Hospitalized in isolation-Removed (SIHR) model, we evaluate
the horizontal and longitudinal effects of stringent interventions implemented
in Wenzhou, a representative urban city of China, where stringent interventions
were enforced to curb its own epidemic situation with rapidly increasing newly
confirmed cases. We found that there were statistically significant treatment
effects of those stringent interventions which reduced the cumulative confirmed
cases of COVID-19. Those reduction effects would increase over time. Also, if
the stringent interventions were delayed by 2 days or mild interventions were
implemented instead, the expected number of cumulative confirmed cases would
have been nearly 2 times or 5 times of the actual number. The effects of
stringent interventions are significant in mitigating the epidemic situation of
COVID-19. The slower the interventions were implemented, the more severe the
epidemic would have been, and the stronger the interventions would have been
required.
