It is definitely free to apply for a health certificate in Nanjing now. But only in Nanjing or the city (district) county health bureau (epidemic prevention station) for free.
The health certificate is valid for one year, and the interval between two processing is 1 1 month. If it is lost, it will not be reissued in principle. If it is really necessary to reissue it, it is necessary to provide the above-mentioned valid certification materials before handling it.