US administers 1st doses of Pfizer coronavirus vaccine

 The rollout of the first coronavirus vaccine began Monday morning as the first doses of the Pfizer medication was administered to health care workers and nursing home staffers.

© ABC News Sandra Lindsay, RN, a critical care nurse at Long Island Jewish Medical Center is the first person to be vaccinated in New York, Dec. 14, 2020.

A doctor from Northwell LIJ Medical Center on Long Island was vaccinated at 9:23 a.m. during a livestreamed event with New York Gov. Andrew Cuomo. "You didn't flinch," Cuomo said.

© ABC News Sandra Lindsay, RN, a critical care nurse at Long Island Jewish Medical Center is the first person to be vaccinated in New York, Dec. 14, 2020.

The University of Louisville Hospital in Kentucky will receive its first delivery of the vaccine at 9:30 a.m. and at 10:30 a.m., three doctors and two nurses will receive the vaccine.

Other locations in Connecticut, New York, Iowa, Washington, D.C., and Michigan are also expected to administer vaccine doses on Monday.

MORE: A breakdown of the Pfizer vaccine and why most people will qualify for the injection

The rollout comes less than a week after the U.S. Food and Drug Administration authorized the vaccine for emergency use for Americans over 16. The order from the FDA led to the pharmaceutical company shipping 2.9 million doses to 636 sites across the country.

© Rey Del Rio/Getty Images Shipments of the Pfizer-BioNTech COVID-19 vaccine are loaded into a UPS plane on Dec. 13, 2020 in Lansing, Michigan.

Pfizer, which produced the vaccine alongside German company BioNTech, began shipping the doses from its Michigan warehouse Sunday directly to those sites, which were pre-selected by governors and local health officials.

Pfizer said it would roll out a second batch of 2.9 million doses shortly after the first batch. The U.S. government is opting to keep 500,000 doses in reserve to address any shipping or distribution mishaps.

The vaccine, which requires two doses for full inoculation, began distribution in the United Kingdom last week.

The vaccine is the first in the country to use the genetic technology mRNA instead of viral components. Pfizer claimed its trials showed the vaccine was 95% effective at preventing symptomatic COVID-19.

© Morry Gash/Reuters Boxes containing the Pfizer-BioNTech COVID-19 vaccine are prepared to be shipped at the Pfizer Global Supply Kalamazoo manufacturing plant in Portage, Michigan, Dec. 13, 2020.

The FDA will hold a hearing on Dec. 17 with Moderna, which also developed an mRNA-based vaccine, before possibly giving emergency authorization for its deployment.

Moderna said its clinical trials showed the vaccine was 94% effective at preventing the coronavirus and trial patients who had the vaccine had elevated antibodies in their system three months after the vaccines were administered.

According to the World Health Organization, there are 52 COVID-19 vaccines in human trials, and 162 vaccines in preclinical development.

The vaccine developments come as the U.S. is in the midst of the deadliest period of the pandemic, according to health data. America leads the world with over 16 million cases and close to 300,000 deaths, according to Johns Hopkins University's Coronavirus Resource Center.

The seven-day averages of new daily cases, 211,494, hospitalizations, 106,656, and deaths, 2,427, were at record highs on Dec. 13, according to health data from the COVID Tracking Project.

ABC News' Arielle Mitropoulos, Sony Salzman and Eric Strauss contributed to this report.

This report was featured in the Monday, Dec. 14, 2020, episode of “Start Here,” ABC News’ daily news podcast.

“Start Here" offers a straightforward look at the day's top stories in 20 minutes. Listen for free every weekday on Apple Podcasts, Google Podcasts, Spotify, the ABC News app or wherever you get your podcasts.

US administers 1st doses of Pfizer coronavirus vaccine