Section 9A. A county, except Worcester county, by vote of the county commissioners, a city having a Plan D or a Plan E charter by majority vote of its city council, any other city by vote of its city council, approved by the mayor, a regional school district by vote of the regional district school committee and a district by vote of the district at a district meeting, may provide that it will pay one-half of the amount of the premium to be paid by a retired employee under the first sentence of section 9. A town shall provide for the payment by vote of the town at a town meeting or if a majority of the votes cast in answer to the following question which shall be printed on the official ballot to be used at an election in said town is in the affirmative:— ”Shall the town pay one-half the premium costs payable by a retired employee for group life insurance and for group general or blanket hospital, surgical, medical, dental and other health insurance?”