Taiwan experience of COVID19 infection control

Since COVID-19 pandemic announced by WHO in earlier March 2020, three to five waves regarding the resurgences of epidemics around the world have been notified, claiming a total of 4.5 million deaths among 210 million confirmed cases by the end of August, 2021. Confronted with the threat of COVID-19 pandemic, a series of non-pharmaceutical interventions (NPIs) and pharmaceutical interventions have been adopted by countries to mitigate and control the COVID-19 pandemic. NPIs play a crucial role in controlling COVID-19 pandemic in the year 2020, whereas vaccination have become the mainstay in year 2021. However, new challenges of the global resurgence of COVID-19 pandemic caused by variant of concerns (VOCs) that not only increase transmissibility but also result in vaccine breakthrough via the escaped immune response, many countries around the world have experienced repeated outbreaks alternating between lifting and operating NPIs before and after era of vaccination. To accommodate both scenarios in the presence and in the absence of community-acquired outbreak during COVID-19 pandemic, various epidemic surveillance models, taking into account the impact of SARS-CoV-2 variants, should be adopted to develop the optimal containment measures and mitigation strategies to control epidemics, making allowance for social and economic activities during long-lasting COVID-19 pandemic.
The Taiwan COVID-19 surveillance models are proposed here to demonstrate how to contain COVID-19 epidemics evolving with SARS-CoV-2 variants from January 2020 to August 2021, which is further divided into two phases, the non-VOC (consisting of wild type and D614G) phase and VOC (mainly including Alpha, Beta, Gamma, and Delta VOCs) phase. Two kinds of the epidemic surveillance model are proposed. When there was no community-acquired outbreak during the first non-VOC phase without high alert level of NPI, the epidemic surveillance model is to monitor imported cases for earlier detecting cluster infection of resultant domestic cases caused by all possible transmission routes through the close contact with imported cases among susceptibles. In the presence of community-acquired outbreak during the VOC phase with high alert level of NPI, the epidemic surveillance model with the SEIR underpinning is to evaluate whether, how, and when NPIs and vaccine, if available, can end each episode of community-acquired infection. The empirical results of Taiwan experience in containing COVID-19 with two epidemic surveillance models will be presented.
Containing the epidemic of COVID-19 with various epidemic surveillance models are presented. Applications and results provide new insight into evidence-based interventions, covering NPIs, testing, vaccine, and anti-viral therapy.

Keywords: COVID-19; SARS-CoV-2 variants; Variant of Concerns (VOCs); NPIs vaccine; Epidemic surveillance