Marin is pivoting its vaccine distribution strategy as thousands of appointments go unfilled. Mass vaccination sites are closing at the end of the month in favor of mobile operations like this one, photographed above last week at the Inverness firehouse. Pharmacies, hospitals and clinics will also continue to offer the vaccine, with no appointments required. More than 82 percent of residents over age 16 have received their first dose, leaving 39,827 eligible residents unvaccinated. The county is anticipating federal authorization of a vaccine for people ages 12 to 15 within the next month. The county is home to about 4,000 people in this group, and Marin aims to have all of them vaccinated within one week of the announcement by setting up sites at schools, said Dr. Matt Willis, Marin’s public health officer. In the past two months, just 10 cases of Covid-19 were reported in West Marin.   Dav