Local officials and health professionals continue to expand access to Covid-19 vaccines on the South Fork. Stony Brook Southampton Hospital will hold a pop-up vaccination clinic at the Montauk Playhouse on Thursday to administer the Moderna vaccine and there is a pediatric vaccination clinic slated for next week in East Hampton for children 12 to 18, following the C.D.C.'s emergency use authorization of the Pfizer vaccine for that age group on Wednesday.