Covid-19 vaccines: Two doses of Pfizer and Moderna’s vaccines are necessary, officials say, but questions still linger

He later clarified with a second tweet that he wasn’t recommending that it was 100% the way to go, but that it was worth “giving states the flexibility to try it.” Although 80.5 million vaccine doses have been administered in the United States and the single-dose Johnson & Johnson vaccine is entering the US supply, […]