Certificate of insusceptibility to successful vaccination.

If any vaccinator finds that any person or child whom he has thrice vaccinated unsuccessfully is insusceptible to successful vaccination or that the child or person who is brought or comes to him for vaccination has already had small-pox, he shall deliver to the guardian or person concerned a certificate under his signature in the prescribed form and the guardian shall not thenceforth be required to cause the child or the person to get himself to be vaccinated.