Section 7A. The commissioner, with the approval of the secretary of health and human services, may designate certain physicians and dentists employed by the department as public health officers; provided, however, that there shall be not more than ten public health officers in the department at any one time. In order to be eligible to be designated as a public health officer, an employee shall have received a doctor of medicine, doctor of dental medicine or equivalent degree from an accredited medical or dental school, and shall be fully registered to practice medicine or dentistry in the commonwealth, and shall be serving in a management position classified as a program manager specialist allocated to Job Group M–VII, M–VIII, M–IX, M–X, M–XI or M–XII in the management salary schedule in section forty-six C of chapter thirty. The salaries of the positions in which public health officers are serving shall, however, be determined in accordance with the provisions of paragraph (5A) of said section forty-six C and shall not be subject to paragraph (4) of section forty-five of said chapter thirty.