The validity period of most nucleic acid testing reports is 1 week from the date of patient testing, and the incubation period of novel coronavirus is about 14 days. The negative test usually proves that the body is not infected with COVID-19 virus, and it is necessary to check the nucleic acid test again after 7 days to determine whether there is COVID-19 infection. The nucleic acid code formed by the nucleic acid test report can be reused within 7 days of validity.