Do not display health codes. Is it safe to issue a paper certificate 24 hours a day?

No, it's not safe. If what is required is a 24-hour nucleic acid certificate, it is impossible and safe not to show it for 24 hours, because the results are not available and there are certain risks. Besides, it's useless to print out a paper version. If it is required to be within 48 hours, the same is true, and the results must be displayed.