With the authorization of the first two COVID-19 vaccines by the Food and Drug Administration, the U.S. has officially embarked on the first phase of the largest mass-vaccination effort in American history. That effort — which is critical to getting control over a pandemic that has hobbled the nation, infected more than 17.5 million Americans, and led to more than 313,000 deaths — faces some daunting logistical challenges and will continue, at the very least, well into 2021.

Below is an overview of the U.S. plan thus far, the hurdles that remain, the vaccines themselves, and various other concerns and questions.

What is the U.S. government’s current plan?

Once COVID-19 vaccine candidates receive emergency-use authorization from the FDA, rollout is expected to begin as soon as 24 hours later. The first vaccine candidate to gain that authorization was the Pfizer-BioNTech vaccine on December 11. Next up was the Moderna vaccine, which the FDA authorized on December 18. Among the first Americans to receive a dose of the Pfizer vaccine was intensive-care nurse Sandra Lindsay, who was given a shot on Monday, December 14, at Long Island Jewish Medical Center in Queens.

The U.S. has worked to rush coronavirus-vaccine availability through a multibillion-dollar federal program called Operation Warp Speed, which is aimed at fast-tracking the development, testing, regulatory approval, and distribution of COVID-19 vaccines. The U.S. has already pre-purchased hundreds of millions of doses of various vaccine candidates sight unseen, and the Trump administration has vowed that at least the initial round of vaccinations will be available to all Americans free of charge. It expects to be able to vaccinate about 20 million people by the end of December, and then an additional 20-25 million people in January.

Though federal guidelines will be in place for early distribution, as it has with most aspects of the pandemic, the Trump administration has left most of the decision-making and distribution logistics to states, and Congress so far has allocated no federal funding for vaccine distribution. The Centers for Disease Control and Prevention and the Department of Defense have asked states to provide a list of five options for sites for receiving, storing, and administering a vaccine that requires ultracold refrigeration.

What logistical hurdles loom?

Providing COVID-19 vaccines for even part of the U.S. population will be an enormous logistical challenge involving a complicated supply chain filled with potential bottlenecks, not to mention hundreds of millions of vaccine doses that must each be kept at the right temperature every step of the way, then administered twice, after varied intervals of time, in order to be effective.

To convey a sense of the challenge, here are just some of the various players who will be involved:

  • Several federal agencies, the U.S. military, and a relatively hands-off current presidential administration that has struggled with its pandemic response and has often tried to ignore scientific advice.
  • Countless agencies and authorities at the state and local level, including lawmakers and public-health officials, in 50 states and 14 U.S. territories with different demographics and needs, as well as their own individual plans, preparations, and funding challenges with regard to distributing the vaccines. Along with designated vaccine administration sites, they will have to not only line up recipients for the vaccine, but for a first and second dose separated by 3-4 weeks. In addition, many of these public officials have what could be called, at best, a mixed record on handling the pandemic thus far.
  • Pharmaceutical companies and their manufacturing operations, some of which are overseas.
  • The U.S. health-care system, including countless public and private health-care facilities, all of which are already under enormous strain from the pandemic and a still-surging wave of COVID-19 cases.
  • Manufacturers and suppliers of equipment needed to administer the vaccines, including critical items like medical-grade vials and syringes.
  • Foreign and domestic competition for both the vaccines themselves as well as the supplies needed to properly store and administer them — with global shortages expected, if not inevitable.
  • U.S. health-insurance providers.
  • Companies expected to provide vaccine administration sites like pharmacies and grocery chains.
  • Shipping and logistics companies like UPS and FedEx and at least one major airline.
  • A pandemic-fatigued, politically divided U.S. population, parts of which continue to view the science of COVID-19, or vaccines in general, skeptically.

Who will get the vaccine first, when, and why?

State governors will ultimately make the final decision on who will receive the first doses of the vaccine in the coming days and weeks, most likely based on recommendations made by the CDC. It seems likely that there will be enough doses available in this initial phase to inoculate roughly 20 million Americans.

On December 1, the CDC’s Advisory Committee on Immunization Practices voted to recommend that the two groups that should receive the vaccines first are:

Health-care workers who are most at risk of exposure to COVID-19
This would cover roughly 21 million U.S. health-care workers and help ensure that the people on the front lines battling the coronavirus (and administering vaccinations) remain safe and are able to continue working. Health-care workers account for an estimated 12 percent of U.S. cases and 0.5 percent of U.S. deaths from the coronavirus.

Residents at long-term-care facilities
This would include roughly 2 million U.S. residents of nursing homes and other long-term-care facilities, a group that has been disproportionately devastated by COVID-19 — according to a Kaiser Family Foundation analysis, accounting for 40 percent of all U.S. deaths from COVID-19.

If, as expected, the drug companies produce enough doses by the end of the year to inoculate 20 million people, that would leave out roughly 3 million individuals from the above groups, with state authorities forced to make the difficult decision of who does and does not get vaccinated first.

On December 14, the first of 2.9 million vaccine doses were shipped out to the states, according to Operation Warp Speed CEO General Gus Perna. Only 145 sites actually received the doses on December 14, however, with the fully 2.9 million to be distributed by Wednesday December 16.

When will the general public be able to get vaccinated?

Regarding who will be next in line for the subsequent rollout phases, the ACIP has named as priority groups “workers in essential and critical industries, people at high risk for severe COVID-19 illness due to underlying medical conditions, [and] people 65 years and older.” In an ACIP meeting in September, the agency estimated that there are as many as 80 million essential workers and 53 million people above the age of 65 — all of whom would require two doses each.

But key questions remain, particularly in the determination of which underlying medical conditions will inform vaccine prioritization. While the CDC notes that illnesses being considered are ones that put individuals at higher risk of hospitalization or death, many underlying conditions — including those with heart failure, cancer, or sickle-cell disease — are on that list. Another health condition that the agency is considering is obesity, which, according to one study, makes individuals 113 percent more likely to be hospitalized, 74 percent more likely to be admitted to intensive-care units, and 48 percent more likely to die of COVID-19. Governors will also face the challenge of determining whether and how to factor in race, as Black, Indigenous, and Latin Americans have experienced disproportionate rates of hospitalization and death owing to the coronavirus — and systems will probably vary widely among states.

Members of the general public who are not in high-risk groups will probably be able to start getting access to COVID-19 vaccines beginning in the early spring, and experts seem optimistic that, if everything goes according to plan, most Americans will be able to be vaccinated by June.

And again, it’s important to remember that the CDC recommendations are just non-binding guidelines, and governors will have final say. “They’re going to tell us which hospital, which pharmacies, where they would like it to go,” Health and Human Services Secretary Alex Azar has said. “And they will be determining which groups to be prioritized.”

Which vaccines will be available first?

The first two U.S. authorized vaccines, made by Pfizer-BioNTech and Moderna, both use cutting-edge messenger RNA, or mRNA, technology — which means the vaccines use genetic material to provoke an immune response. It is the first time the FDA has approved mRNA vaccines for human use. mRNA vaccines can be developed faster, which is why these two are at the front of the pack. However, they also require colder freezer temperatures than traditional vaccines normally do, which will make them more difficult to widely distribute and administer.

A third vaccine candidate nearing the FDA approval process, from AstraZeneca–Oxford, is a more traditional recombinant vector vaccine developed by piggybacking virus cells onto another virus (in this case, the virus that causes the common cold).

All three vaccine candidates that have received or are nearing emergency FDA approval will require two doses, which makes distributing and administering them properly, as well as supplying them in sufficient quantities, more complicated.

Are there safety concerns around the new vaccines?

No serious safety concerns were revealed in the three vaccines’ testing trials, according to the pharmaceutical companies that made them. Though no vaccines have ever been developed this fast and the safety data has not been released in full, there does not seem to be much concern about them among vaccine experts. mRNA vaccines in particular are considered especially safe since they only incorporate some of the virus’s genetic material, not the whole virus. (They may, however, have higher potential for short-term side effects, including fevers and aches.) It is not yet clear how long the COVID-19 immunity provided by any vaccines will last.

Will anyone get to choose what vaccine they get?

It is highly unlikely that Americans will be offered a choice of which vaccine they can get anytime soon, but rather they will receive whatever vaccine happens to be available at the time they are eligible to get one. That luxury of choice may be possible sometime next year, when far more vaccines are likely to be available.

Once there are multiple vaccine options, as well as a lot more data about how the various vaccines work for specific groups of people, doctors are likely to prescribe specific vaccines in certain circumstances. CNN explains:

AstraZeneca’s vaccine uses what’s called a replication deficient virus to deliver a piece of genetic material from the coronavirus. So does Johnson & Johnson’s vaccine. There’s not a lot of safety data about these vaccines yet, but some doctors may be reluctant to offer them to patients with compromised immune systems, including those with rheumatoid arthritis or multiple sclerosis who are taking immune-suppressing drugs; pregnant women; people taking certain cancer treatments and others.

How long will the vaccines provide immunity against COVID-19?

Because of the shorter-than-normal length of trials being used to evaluate the vaccines, it is not yet known what duration of protection they provide against COVID-19. It’s worth remembering that scientists still don’t know how long immunity from a COVID-19 infection lasts, either.

Where and how will the vaccines be administered?

According to Operation Warp Speed, the sites where the vaccines will be administered in each state include:

  • Hospitals
  • State health departments
  • Clinics and doctors’ offices
  • Pharmacies and some grocery-store chains
  • Long-term-care facilities
  • Military treatment facilities
  • Certain federally run sites

Hospitals and state health departments will likely receive the first available vaccines. It will be up to each state and facility to determine how it handles the process of administering the vaccines.

The deep refrigeration required to store early vaccine candidates, including Pfizer’s, may preclude some sites from being able to administer those vaccines, since it’s the rare urgent-care facility that has a freezer that gets down to minus-70 degrees Celsius. Pharmacy and grocery chains that have signed on with Operation Warp Speed include Kroger, Albertsons, and CVS. Firms involved in the program have been purchasing medical-grade freezers to store vaccine doses, while long aisles within stores themselves will allow for those waiting for vaccines to distance themselves in line. CVS and Walgreens are already trying to hire tens of thousands of workers nationwide in preparation for the vaccine distribution push.

Will Biden change the federal government’s approach, and if so, how?

There is pretty much nothing President-elect Joe Biden can do regarding the distribution of vaccines before he takes office on January 20, when his administration will take over management of the federal response to the pandemic and distribution of the vaccine. The Trump administration finally stopped blocking Biden’s transition team from meeting with the White House coronavirus task force and Operation Warp Speed officials on November 23.

Biden has already formed a pandemic task force to advise his administration on how to handle the pandemic, and the president-elect has vowed that his administration’s approach will be led by science. It seems certain that Biden, as president, will not only continue but work to expand the Trump administration’s efforts to provide Americans the coronavirus vaccines free of charge. During his campaign, Biden called for $25 billion of federal spending to “guarantee [the vaccine] gets to every American, cost-free.” More funding will undoubtedly be needed, but it’s not clear how much Biden will be able to come up with without congressional authorization (and which political party controls the Senate won’t be determined until the results of a pair of runoff elections on January 5 in Georgia are known).

On December 8, Biden revealed his plan to confront the pandemic, including the goal of making sure at least 100 million Americans get vaccinated within his first 100 days in office (by the end of April). He also confirmed that his administration would follow CDC recommendations regarding who gets the vaccine first, and work to make sure teachers and other educators were vaccinated as soon as possible.

The New York Times has reported that Biden transition officials are discussing two new policies regarding the vaccines: making COVID-19 vaccinations mandatory, and coming up with a secure way for people to be able to prove that they have been vaccinated.

It’s also possible that President Trump — who has notoriously worked to downplay the threat of the virus throughout the pandemic and had refused to acknowledge the legitimacy of Biden’s election win — will publicly oppose some or all of whatever policies Biden ultimately decides to implement. If he does that, it’s far from clear what impact it would have among his supporters and allies.

How much will the vaccines cost?

The Trump administration has promised to offer the COVID-19 vaccines to the public free of charge, at least initially, and has already invested nearly $8 billion to purchase hundreds of millions of doses. The plan is for at least the first round of coronavirus vaccinations to be available free of cost to everyone, including those without insurance. However, as is always the case with anything to do with the American health-care system, it remains to be seen how, exactly, that will all play out once the billing actually starts. (Another pertinent question: how millions of undocumented migrants living the United States will access the vaccine.)

For instance, there is the matter of possible administration or office-visit fees charged by the vaccine providers, which, according to the CDC, can be reimbursed by insurers, or, for the uninsured, by the Health Resources and Services Administration’s Provider Relief Fund. How easy that will be for the uninsured is not clear.

It’s also worth noting that the vaccine would have already been free for the vast majority Americans with insurance, as the Affordable Care Act requires insurers to cover any federally recommended vaccines with no out-of-pocket costs. That does not apply, however, to people on short-term plans, which have no federal coverage requirements. (The Kaiser Family Foundation has published a very detailed rundown of all the variables regarding potential vaccine costs to the public.)

As far as how much individual vaccine doses will cost the government or insurance companies, the current leading vaccine candidates are expected to cost anywhere from $3 to $37 per dose.

How long will the federal government offer the vaccines for free?

It’s not clear if or how the costs will be covered beyond the rollout or if a second round of vaccinations is needed at some point in the future, which depends on how long immunity lasts under the various vaccines. Here’s how the Kaiser Family Foundation summarizes these unknowns:

The federal government has already paid for several hundred million doses of multiple COVID-19 vaccines through Operation Warp Speed, even before clinical trials have been completed. Under the terms of Operation Warp Speed, the federal government has the option to purchase hundreds of millions of additional doses. It remains unclear how many additional doses of COVID-19 vaccines may eventually be needed, by when, and how long immunity will last under a COVID-19 vaccine. If, in the future, the COVID-19 vaccine becomes a regular, annual vaccine, it is expected that it would eventually be covered through the same programs and types of insurance that are currently used to pay for other vaccines. If concerns arise about the eventual cost of COVID-19 vaccine(s) or other vaccines to federal and state governments and private payers, policymakers may look to rules that already govern vaccine pricing and reimbursement in different markets to leverage the government’s buying power.

Will COVID-19 vaccination be mandatory?

It’s possible the vaccine will eventually be made mandatory at either the federal, state, or local level, but that hasn’t happened yet. It’s also possible that employers or schools could mandate COVID-19 vaccinations. How or when such decisions may be made, their legality, and how those mandates would be enforced is not clear. It’s also not clear when the vaccines will be widely available enough for mandates to even be realistic.

Can you tell me more about the first-wave vaccines?

Here are more details about these first three vaccine candidates, their efficacy, U.S. availability timetables, and differences.

Pfizer-BioNTech vaccine
The first COVID-19 vaccine authorized for U.S. distribution is made by Pfizer. The company applied for emergency-use authorization from the FDA on November 20, and the FDA issued an emergency use authorization for the vaccine on December 11. (The U.K. approved the Pfizer vaccine for human use on December 2 and began vaccinating people with it on December 8.) The biggest issue regarding the distribution of the vaccine is the extreme cold it must be stored at, necessitating the use of both specialized ultracold shipping and freezers. This will undoubtedly make the vaccine the most difficult of the early candidates to distribute and administer.

  • Earliest possible availability: States began receiving and administering doses of the Pfizer vaccine on December 14.
  • Initial quantity: 2.9 million doses were initially slated for the first round of distribution. Pfizer has said it is ready to ship 20 million doses at rollout, which would inoculate 10 million people. It says it will have manufactured enough of the vaccine to inoculate 25 million people in the U.S. by the end of the year.
  • Efficacy: Was found to be 95 percent effective in clinical trials with no serious safety concerns. The vaccine is likely to provide some protection from COVID-19 after the first dose, but not the full possible protection until after the second dose.
  • Dosage/timing: Requires two doses, with the second shot administered three weeks after the first one.
  • Storage requirements: Must be stored frozen at the ultracold temperature of minus-70 degrees Celsius.
  • Cost to the U.S. government: Estimated to be about $20 per dose.
  • Additional notes: Pfizer will ship the vaccine in specialized cases equipped with dry ice and GPS trackers to ensure the vaccine remains at the proper temperature while en route to administration sites.
  • Type: mRNA vaccine

Moderna vaccine
The second COVID-19 vaccine available for U.S. distribution was Moderna’s. The company applied for emergency-use authorization from the FDA on November 30, and received it on December 18. The Moderna vaccine’s storage temperature requirements are less extreme than Pfizer’s.

  • Earliest possible availability: As soon as December 21.
  • Initial quantity: Moderna has said it will be able to ship 20 million doses to the U.S. at rollout, which would inoculate 10 million people. 5.9 million doses will be distributed the first week.
  • Efficacy: Was found to be 94 percent effective in clinical trials with no serious safety concerns.
  • Dosage/timing: Requires two doses, with the second shot administered four weeks after the first one.
  • Storage requirements: Stored at a temperature of minus-20 degrees Celsius, but will keep for a month at refrigerator temperatures.
  • Cost to U.S. government: Expected to be $15 to $25 per dose.
  • Additional notes: Because it can be stored in less-extreme cold than the Pfizer vaccine, the Moderna vaccine may be easier to distribute to areas without access to specialized freezers.
  • Type: mRNA vaccine

AstraZeneca-Oxford vaccine
AstraZeneca announced the trial results for its vaccine on November 23 and is expected to apply for emergency-use authorization from the FDA soon.

  • Earliest possible availability: Maybe by the end of the year.
  • Initial quantity: The company has said it will be able to supply 200 million doses globally by the end of 2020. It’s not clear how many of those will be exclusively available for the U.S. at rollout.
  • Efficacy: Was found to be around 90 percent effective in clinical trials with no serious safety concerns. However, the vaccine was found to be more effective when a half-dose was administered first, followed by a full dose a month later (90 percent effective), as opposed to two full doses (62 percent efficacy). The efficacy of a single dose by itself is still be tested in trials.
  • Dosage/timing: Will require two doses.
  • Storage requirements: Can be stored at normal refrigeration conditions for at least six months.
  • Cost to the U.S. government: Estimated to be $2.50 a dose.
  • Additional notes: This vaccine is expected to be the cheapest of the early candidates, and because the vaccine doesn’t require freezers for storage and has a longer shelf life, it would be the easiest, logistically, to distribute and administer. However, there has also been some well-founded confusion over the vaccine’s dosage and efficacy, after experts reviewed the trial data released by AstraZeneca.
  • Type: Recombinant vector vaccine

Other vaccine candidates
Per the CDC, two other pharmaceutical companies’ COVID-19 vaccines are in or nearing large-scale phase-three clinical trials for U.S. usage. Janssen’s recombinant vector COVID-19 vaccine (also known as the Johnson & Johnson vaccine) is currently in phase-three trials and could be available next year. Meanwhile, Novavax is getting reading to start phase-three clinical trials for its protein-based COVID-19 vaccine.