(NBC News) A second vaccine is now in use in the fight against COVID-19.
Millions of Moderna doses were delivered to thousands of locations nationwide Monday.
Clinical trials show it's as effective as Pfizer's vaccine, but doesn't require subzero storage.
Meanwhile, President-elect Joe Biden received his first dose of Pfizer's vaccine.
This week CVS and Walgreen's will begin administering vaccines to residents of long term care facilities.
A Center for Disease Control advisory committee recommends the next phase of distribution include Americans 75 and older and front line workers like police, teachers and grocery store clerks.
Still, health experts say difficult days are ahead.
"Vaccinations are really not going to impact the course of this pandemic until the early spring," warns NBC Medical Contributor Dr. Vin Gupta.
Hospitals in California are reaching critical levels amid the post-Thanksgiving surge in infections.
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