flurry of mandatory evacuations issued in the last hour. bill. >> whitaker: thank you, jonathan. that is a beautifully deeply forested part of california. so tragic. tonight, there's news about one of the covid vaccines. moderna say its shot remains effective at least six months after the second dose, though it expects booster shots will be needed this winter. vaccinations are up this week, but so are new covid cases, and there's concern about a potential superspreader event in south dakota. cbs' mola lenghi is there. >> reporter: more than half a million bikers are expected to ride into the small town of sturgis, south dakota over the next ten days as the delta variant rips through the nation. besides the bikes and beers, most are here for something many americans can probably relate... >> tired of living in-- staying at home and we're ready to get out and do stuff. >> tired of living in fear. >> reporter: mark and jackie