; vacancies After its initial meeting, the Commission shall meet upon the call of the chair or a majority of its members. Six members of the Commission shall constitute a quorum. Any vacancy in the Commission shall not affect its powers, but shall be filled in the same manner in which the original appointment was made. (4) In-person meetings The members of the Commission shall conduct its meetings in person unless such in-person meetings would pose a health risk or significant practical challenges. (d) Functions of Commission The functions of the Commission are to— (1) conduct an investigation that— (A) addresses the matters specified in subsection (b); (B) investigates relevant facts and circumstances relating to the outbreak and spread of COVID–19 in the United States, and the response to such outbreak and spread, including with respect to any relevant legislation, Executive order, regulation, plan, policy, practice, or procedure; and (C) may include relevant facts and circumstances relating to— (i) Federal, State, and local authorities with responsibilities relevant to the outbreak and spread of COVID–19 in the United States, including such authorities with responsibilities relating to public health, emergency management, and epidemic and pandemic preparedness and response; (ii) private sector organizations; (iii) intelligence agencies and law enforcement agencies; (iv) diplomacy and international coordination; (v) immigration and border control; (vi) the role of congressional oversight and resource allocation; and (vii) other activities of the public and private sectors determined relevant by the Commission for its inquiry