No nucleic acid was recorded in 14 days. What do you mean?

The significance of 14 effective negative nucleic acid record could not be found. In daily life, when users use health codes, if there is no nucleic acid record for 14 days, it means that there is no effective negative nucleic acid record for 14 days. Health Code is a tracking and judging system of personal health information and activity information used for epidemic prevention and control in COVID-19.