Andrew Noymer, a UC Irvine [associate] professor of population health and disease prevention, said he’s pleased at the progress Orange County has made so far, especially since adults face greater risk from the coronavirus than children. But, he added, that pleasure comes with some caveats. “Herd immunity is a moving target. … The COVID-19 vaccines kick ass. Public health has given us the best weapon against this and that is a great vaccine — now we have to use it,” Noymer said.