LIBERTY, Mo. (AP) — Missouri health officials say they are optimistic efforts to provide COVID-19 vaccines will expand soon, both in terms of increased vaccine availability and the number of approved vaccinators. Dr. Randall Williams, head of the state health department, said Wednesday Missouri expects to receive a significant amount of a new Johnson & Johnson vaccine, which requires only one shot, next month.  At the same time, vaccinations will begin Friday at some Walmart and Sam’s Clubs, and the state will begin using retired health care workers to administer the shots. The positive message came as Gov. Mike Parson complained to Missouri mayors about constant criticism in the media about the state’s vaccination efforts.