There shall be a provision that written notice of sickness or of injury must be given to the insurer within 30 days after the date when such sickness or injury occurred. Failure to give notice within such time shall not invalidate nor reduce any claim, if it shall be shown not to have been reasonably possible to give such notice and that notice was given as soon as was reasonably possible. [PL 1969, c. 132, §1 (NEW).]