31. In any prosecution for neglect to procure the vaccination of child it shall not be necessary in support thereof to prove that the defendant had received notice from the Registrar or any other officer of the requirements of the law in this respect;but, if the defendant produce any such certificate as herein before described, or the duplicate of the register of births or the register of postponed vaccinations kept by the Registrar as hereinbefore provided, in which such certificate shall be duly entered, the same shall be a sufficient defense for him, except in regard to the certificate according to the form of the said Schedule A, when the time specified therein for the postponement of the vaccination shall have expired before the time when the information shall have been laid.