National News Second doses of vaccine a must as variant spreads, doctors say Since the nation's vaccination efforts began in December, millions have received a full dose of the COVID-19 vaccine, but as the original virus and its variants spread, health experts say there are concerns about another group — those who received the first dose of two-dose courses like Pfizer and Moderna but not the second. Jul. 10 2021 @ 7:34pm PITTSBURGH — Since the nation's vaccination efforts began in December, millions have received a full dose of the COVID-19 vaccine, but as the original virus and its variants spread, health experts say there are concerns about another group — those who received the first dose of two-dose courses like Pfizer and Moderna but not the second.