With 18 deaths already linked to the illness, Massachusetts health officials say this is the worst flu season in Massachusetts in a decade.  Free city-run flu clinics are being canceled in some parts of the state because cities, including Somerville, have run out of vaccine.  But the news is better in Northampton where a free flu clinic is being held on Saturday.  The clinic is being run by the VNA and Hospice of Cooley Dickinson Hospital.  It'll be held at the new Greenfield Savings Bank branch on King Street from 9 am to noon.  The fee is being waved, but many insurances pay for flu vaccines, so those attending are asked to bring their insurance card.  No appointment is necessary to get a flu shot.