News Pfizer vaccine appears effective against asymptomatic cases; feds plan to ramp up vaccinators, sites: COVID-19 updates March 12, 2021March 12, 2021 Elinor Aspegren and Ryan W. Miller, USA TODAY Comments Off on Pfizer vaccine appears effective against asymptomatic cases; feds plan to ramp up vaccinators, sites: COVID-19 updates Data from Israel suggests Pfizer vaccine appears effective against asymptomatic COVID-19 cases. Latest coronavirus updates.