West Virginia will begin offering some fully vaccinated people free tests to measure antibody levels against the coronavirus. State health officials said the move will help study whether some elderly and immunocompromised people should receive a third booster shot. The state will offer antibody testing for residents age 60 and over, particularly those living in nursing homes, who received their final vaccine dose at least six months ago. If the results show their antibody levels are low, a booster shot may be recommended to shore up the body’s protection against the virus.