(Portland, OR)  --  The COVID-19 mass vaccination clinic at the Oregon Convention Center will start taking walk-ins without appointments today.  The clinic isn't normally open on Fridays, but they'll be open from 9 a.m. to 4 p.m.  They'll be closed Saturday and Sunday.  They'll return to normal hours on Monday.  They prefer that people make appointments at the All 4 Oregon website.  They hope the ability to offer walk-in vaccinations will make it easier for people who can't make an appointment.