How is nucleic acid positive? Will people who have been infected again? Is the view of "early sun, early good" correct? Is vaccination still necessary at this stage With the increase of COVID-19 infection in society, people's doubts about "Yang excess" and "Yang health" are also increasing. Today, we will summarize and analyze some recent focus issues to help you solve your doubts. How is nucleic acid positive? After a person infected with COVID-19 has been isolated at home for rest or hospitalized, the criteria for de isolation are as follows: 1. The body temperature is normal for more than 3 days; 2. Respiratory symptoms improved significantly; 3. If there is pneumonia, the pulmonary imaging should show that the acute exudative lesions have been significantly improved; 4. The Ct values of N gene and ORF gene of COVID-19 nucleic acid test twice in a row are ≥ 35, or COVID-19 nucleic acid test twice in a row is negative. Those who meet the above conditions are considered to have recovered, are not infectious, and will not have a relapse. However, after the isolation of some infected people was lifted, they went to check the nucleic acid and found it was positive again. If it can be ruled out that it is positive due to the second infection, this situation is usually referred to as "nucleic acid re positive". In fact, since the outbreak of the COVID-19 epidemic, there have been reports of "nucleic acid reactivation" all over the world from time to time. However, it was finally found that what was detected was the viral "nucleic acid fragments" in the respiratory specimens, and there was no live virus, nor was it found that these nucleic acid reactivation groups transmitted the virus to the surrounding people. That is to say, people with "nucleic acid positive" are not infectious and will not have related symptoms again, so we do not need to worry about this. Will he get hurt again after he recovers? Although "nucleic acid reactivation" is not infectious and will not lead to repeated symptoms, re infection is different. According to clinical experience, patients who have been infected with COVID-19 may be infected again, or even infected three times. What's the matter? One factor that determines the risk of secondary infection is the antibody level. COVID-19 is a highly contagious respiratory infectious disease. People can obtain antibodies against the infected strains after infection. The antibody level is relatively high in the short term, and the risk of reinfection is low. However, as time goes on, the level of antibody will gradually decline, and people will face the risk of re infection. At present, it is generally believed that the risk of reinfection will increase significantly in patients who recover from infection after 3 to 6 months. Due to the degeneration of immune function, the protection period of the elderly will be shorter; The immune function of infants is not perfect, and the risk of reinfection is high; The protection period of people with immune deficiency (such as AIDS patients, those who use corticosteroids or other immunosuppressive drugs for a long time to lead to the decline of immune function) will also be shorter. In contrast, people with good immune function, such as young people, have a longer duration of protection and a low risk of re infection in the short term. In addition, it should be noted that respiratory infectious diseases enter the human body through the respiratory mucosa. Although a certain level of antibody is produced in the body after infection or vaccination, the antibody level under the respiratory mucosa is significantly lower than that in the body. Therefore, whether antibody is obtained after infection or vaccination, it is not satisfactory to prevent respiratory infection, but there are antibodies in the body,