No longer judge the tight connection, cancel the circuit breaker mechanism of inbound flights, adjust the risk area to "high and low", correct the unscientific practices of nucleic acid testing, such as "two checks a day" and "three checks a day", and accelerate the drug reserve related to the treatment of COVID-19... After the publication of 20 optimization measures, it has aroused widespread concern in the society. Twenty optimization measures have been implemented in various regions. How to delimit the risk area? How to determine the tight connection and space-time adjoint? Is it necessary to insist on doing nucleic acid? Focusing on the hot issues of public concern during the implementation process, relevant experts of the joint prevention and control mechanism of the State Council made authoritative responses. Question 1: Does twenty optimization measures mean relaxing prevention and control? Will it increase the risk of epidemic transmission? A: The optimization and adjustment of prevention and control measures is not to relax prevention and control, nor to open up and "lie flat", but to adapt to the new situation of epidemic prevention and control and the new characteristics of COVID-19 mutation, adhere to the established prevention and control strategies and guidelines, and further improve the scientific and precise nature of prevention and control. These adjustments are based on the experience summary and relevant assessment data of epidemic prevention and control practices in many places. In recent three years, China has optimized and adjusted the prevention and control measures according to the global epidemic situation and virus variation, combined with the practical experience of epidemic prevention and control in China. Every adjustment and optimization has been repeatedly studied, judged and scientifically demonstrated to ensure positive, stable and controllable risks. The 20 optimization measures are more scientific and accurate measures that seek progress while maintaining stability, take small steps without stopping, conform to China's national conditions. These adjustments require more standardized and faster prevention and control, to control the key risks to be controlled, to put the implementation in place, and to resolutely cancel the cancellation, to make full use of resources and improve the efficiency of prevention and control. Question 2: According to the public, "community outbreak area" and "community communication area" have been proposed. After 20 optimization measures have been proposed, how to define the risk area? A: Twenty optimization measures will change the risk areas from "high, medium and low" to "high and low". Under the premise of scientific and accurate risk area control, the scope of control and personnel will be minimized. According to the practical application of the ninth version of the prevention and control plan and the assessment in July and August this year, the positive detection rate in the medium risk area is about 3/100000, which means that the risk is extremely low. In order to reduce the control area and personnel as much as possible, the delineation of medium risk area has been cancelled. According to the 20 optimization measures, in principle, the living places of infected people and the working places and activity places with frequent activities and high risk of epidemic transmission are designated as high-risk areas. High risk areas are generally designated by units and buildings and cannot be expanded at will; Other areas of the county (city, district, banner) where the high-risk area is located are designated as low-risk areas. The high-risk area was reduced to a low-risk area where no new infections were found for 5 consecutive days. High risk areas meeting the unsealing conditions shall be unsealed in time. Problem 3: The masses have reported that there are various judgments such as tight connection and space-time concomitance. What epidemic prevention measures should be taken for different judgments? Answer: Tight contact is the abbreviation of close contact person. Generally, it refers to the person who has close contact with the suspected case and confirmed case but has not taken effective protection 2 days before the symptom appears, or the person who has asymptomatic infection starts 2 days before the sample sampling. The ninth version of the prevention and control plan lists 9 types of closely connected personnel, including living together