Vacancies, other than by reason of expiration of terms, shall be filled for the balance of the unexpired term, in the same manner and by the same body, except elected members in towns whose terms shall be filled in accordance with the provisions of section eleven of chapter forty-one. Every member, unless sooner removed, shall serve until the qualification of his successor.
As soon as possible after the qualification of the members of a housing or redevelopment authority the city or town clerk, as the case may be, shall file a certificate of such appointment, or of such appointment and election, as the case may be, with the department, and a duplicate thereof, in either case, in the office of the state secretary. If the state secretary finds that the housing or redevelopment authority has been organized and the members thereof elected or appointed according to law, he shall issue to it a certificate of organization and such certificate shall be conclusive evidence of the lawful organization of the authority and of the election or appointment of the members thereof.
Whenever the membership of an authority is changed by appointment, election, resignation or removal, a certificate and duplicate certificate to that effect shall be promptly so filed. A certificate so filed shall be conclusive evidence of the change in membership of the authority referred to therein.