- The FDA authorized Moderna's coronavirus vaccine for emergency use on Friday.
- Pfizer's COVID-19 shot got US clearance a week before Moderna's did, and many healthcare workers have already started to receive their shots.
- By late May, it's possible that everyone in the US who wants a shot will have access.
- But it may take several months after that to develop enough herd immunity through vaccination to make mass gatherings safe.
- Visit Business Insider's homepage for more stories.
The US now has two safe, highly effective coronavirus vaccines authorized for use.
The Food and Drug Administration granted Moderna's COVID-19 vaccine an emergency use authorization on Friday. The shot could go into the arms of some of the most vulnerable people in the country - healthcare workers and nursing home residents - within days.
Pfizer's coronavirus vaccine was approved on December 11, and healthcare workers started receiving those shots last Monday.
But most of the country shouldn't ready their arms for a needle just yet. And don't throw away your face masks, either.
It will still take many months for healthcare providers to give these shots to enough members of the public to make a dent in the pandemic. Here are the key milestones to watch out for.
An uneven rollout across the country
December's vaccine authorizations mark a milestone months in the making.
Study volunteers have been receiving Moderna shots since March and Pfizer shots since April. Both companies released safety and efficacy data on those trials in November.
In each case, an FDA advisory committee reviewed the safety data submitted by the company. The committee voted in favor of recommending Pfizer's shot for people ages 16 and older and Moderna's shot for people ages 18 and older.
An advisory group at the Centers for Disease Control and Prevention has recommended that healthcare workers and nursing home residents - around 24 million people in total - be first in line. But ultimately, it's up to each state to decide how to prioritize their shots.
A recent Kaiser Family Foundation report found that 45 states are following the CDC advisory group's recommendation, but a few are veering slightly off course. Nevada, New Hampshire, and Wyoming, for instance, are including law enforcement in their first round of vaccinations, while Massachusetts is including incarcerated people and those in homeless shelters.
After healthcare workers and nursing home residents have gotten a chance to get vaccinated, frontline essential workers and people over 75 should be next in line, the CDC advisory group said in updated recommendations released on Sunday. This second priority group consists of roughly 49 million people across the US, including: first responders, teachers, daycare providers, food and agriculture workers, manufacturers, corrections officers, the US Postal Service, public transit workers, and grocery store employees.
But only 50 million people are expected to receive vaccinations in December and January. Operation Warp Speed then hopes to double that number by March, with 100 million Americans vaccinated by then.
However, earlier this week, US pharmacists discovered something that could help speed up the timeline: Pfizer's vaccine vials seem to contain six or seven doses instead of the five doses described in the FDA guidelines. That could mean the US supply of Pfizer's vaccine is up to 40% bigger, though doses per vial can vary depending on the types of needles and syringes used.
By spring, vaccines could be rolling out to healthy members of the general public
If federal projections hold, roughly a quarter of the US could be vaccinated by spring. Then shots could become more widely available to young, healthy people.
Still, that does not mean that everyone will be able to get their coronavirus shots by April.
"It really is a bit more complicated than that," Dr. Anthony Fauci told reporters in November, explaining that distribution will "be a graduation over a period of months."
"By the time we get through December, January, February, March, April, we hopefully will have been able to get to the people who are listed as priority people," Fauci said. "I would say starting in April, May, June, July, as we get into the late spring and early summer, that people in the so-called general population, who do not have underlying conditions or other designations that would make them priority, could get them."
He added: "This does not mean that in April everybody who is going to be wanting a vaccine who is not a priority group is going to get it. It means starting at that point, you would likely begin."
By Memorial Day, many Americans will likely have access to COVID-19 vaccines
By summer 2021, it's reasonable to expect widespread vaccine access in the US. May 31 - Memorial Day - could be a benchmark moment.
"What I believe is that by Memorial Day, in the US, anybody who wants a vaccine will get a safe and efficacious vaccine," Moderna CEO Stephane Bancel told Business Insider in November.
There is one catch. Both Moderna and Pfizer's vaccines come as two shots, administered several weeks apart. (Moderna's are administered four weeks apart. For Pfizer's shots, it's three weeks in between.)
But it's also possible that by summer, there will be other shots available from drugmakers including AstraZeneca, Johnson & Johnson, and more.
By the end of 2021, it may be safe to host large gatherings again
Both Moderna and Pfizer's vaccines appear to be very effective. Their reported efficacy rates, at around 95%, mean the shots prevent more than nine in ten symptomatic infections. Those success rates are far better than the flu shot and on par with other highly protective vaccines, like those for chickenpox, measles, and polio.
But the process of getting coronavirus vaccines into hundreds of millions of people, thereby developing herd immunity, is likely to take many months.
"The moment you get a vaccine doesn't mean you're going to put your mask in the trash," Maria Elena Bottazzi, a vaccine developer at Baylor College of Medicine, recently told Business Insider.
Fauci told The New York Times in November that "at least 75%, hopefully close to 80, 85%" of the country would need to be vaccinated by fall 2021 in order to get "close to some degree of normality."
"What I would like to see is the overwhelming majority of people get vaccinated so we can, essentially, really crush this outbreak," he said. "This is going to be a difficult task."
Fauci told Insider that it's safer to wait until 2022 to schedule big weddings, birthdays, and other celebrations. Getting "most everybody in the population" vaccinated in the US "could be accomplished by the end of 2021," he said.
Andrew Dunn contributed reporting.