More than 4.2 million vaccine doses have been administered so far in the U.S., according to the CDC.
However, many experts say that's not fast enough - especially since over 13 million doses have already been distributed. That's well short of initial predictions that 20 million people would have received the vaccine by the end of December.
Coronavirus cases have surged in November and December, topping 100,000 hospitalizations for the last 33 consecutive days.
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