The first health workers in the US are receiving the Pfizer/BioNTech Covid-19 vaccine Monday

The first doses of the vaccine are now rolling out to all 50 states.

The United States launched its largest vaccination campaign in history Monday as people began to receive the first doses of the two-dose Pfizer/BioNTech Covid-19 vaccine.

Hospitals in all 50 states have started to receive the vaccine, and health care workers at the front lines of the pandemic are among the first people to receive the injections.

In New York City, Sandra Lindsay, an intensive care nurse at Long Island Jewish Medical Center in Queens, became the first person in the United States outside of a clinical trial to receive the injection.

Mark Lennihan/AP

Mark Lennihan/AFP via Getty Images

The Pfizer/BioNTech vaccine will also be administered Monday in places like Michigan, Ohio, and Washington, DC.

The rollout comes after the Food and Drug Administration granted an emergency use authorization to the Pfizer/BioNTech vaccine on Friday evening. The authorization followed a recommendation from a vaccine advisory committee after reviewing clinical trial data showing that the vaccine was 95 percent effective at preventing disease in people 16 years old and older. The US emergency authorization follows similar clearances in Canada and the United Kingdom last week.

And not a moment too soon: The US is reaching horrific new levels of Covid-19 hospitalizations, with many ICUs around the country overwhelmed. Meanwhile, daily fatality numbers keep climbing, with close to 300,000 total reported deaths in the US since the pandemic started.

The launch of the Pfizer/BioNTech vaccine marks the fastest development effort for a vaccine in history, an endeavor that typically spans decades. In addition, the Pfizer/BioNTech vaccine uses mRNA as its platform, a new technology that has never seen widespread use in humans before.

“In my lifetime, biomedical science has never moved this fast,” said E. John Wherry, director of the Institute of Immunology at the University of Pennsylvania, during a Monday webinar about Covid-19 vaccines. “This would have been absolutely unfathomable just a few years ago that we would move this fast.”

While health care workers and people in long-term care facilities are at the front of the line, these groups add up to about 24 million people, so the first round of vaccine shipments will not be enough for everyone. Some hospital systems are using algorithms to weigh risk factors; others are using lotteries to determine who will be among the first to receive the inoculation.

Operation Warp Speed, the program from the Department of Health and Human Services, is aiming to have enough Covid-19 vaccines to immunize 20 million Americans in December, 30 million more in January, and 50 million more in February as more vaccines gain approval.

Another challenge is that the Pfizer/BioNTech vaccine has stringent cold storage requirements, demanding temperatures of -70°C (-94°F) or lower. While Pfizer says it has developed shipping containers that can safely store the vaccine at the requisite temperatures for up to 10 days, longer storage will require specialized ultra-cold freezers that are only available at a handful of medical facilities, and those places have limited storage space. That means timing the shipments of the vaccine will be critical.

The FDA’s vaccine advisory committee is meeting on Thursday to consider another mRNA-based Covid-19 vaccine, this one developed by Moderna. This vaccine also demonstrated 95 percent efficacy.

The final challenge will be to develop the infrastructure to get the vaccines to 330 million Americans and to convince the holdouts to take them.