This is a picture of what vaccine vials look like.

Researchers around the world have wasted no time in the race to find a vaccine to combat COVID-19. Months into the pandemic, several vaccine candidates are in late-stage clinical trials to test how well they protect people from a coronavirus (SARS-CoV-2) infection. And experts predict that by the end of 2020 or early in 2021, a safe and effective option will emerge.

“This is the scientific world working at warp speed,” Barry Bloom, a professor of immunology and infectious diseases and former dean at the Harvard T.H. Chan School of Public Health, said in a Sept. 15 webinar.

Beyond the development of the medicine itself, efforts to speed up vaccine manufacturing and distribution are also in place. Here’s a look at the coronavirus vaccine prospects and the progress being made on them.

What, exactly, is a vaccine?

A vaccine is something that helps a person build up immunity to an infectious disease. It works by intentionally introducing the body to an inactive form of a disease-causing germ, or something similar to it. This then stimulates the immune system’s production of antibodies, the proteins that help to protect the person from a future infection if they ever come across the real germ.

Think of it like a workout for your immune system: You’re “sending it to the gym and preparing it to be able to do something when it encounters the real thing in the future,” says Tony Moody, M.D., associate professor of pediatrics and immunology at Duke University School of Medicine and a principal investigator at the Duke Human Vaccine Institute. “Essentially, what a vaccine is doing is teaching the immune system how to handle something before you actually encounter the real thing — so that, hopefully, when you do encounter the real thing, you’re able to deal with it quickly and get rid of it.”

In the case of the new coronavirus, a vaccine would make a person resistant to an infection from the virus and the illness it causes — COVID-19 — or, at the very least, make it so that a person who becomes infected has “a shorter course [of disease] or not as many complications,” Moody adds.

Which coronavirus vaccines are leading the pack?

Two are considered the frontrunners in the U.S.: a vaccine from Moderna and the National Institute of Allergy and Infectious Diseases (NIAID) and one from Pfizer and BioNTech.

What makes these vaccines special? The companies behind both vaccines report they are highly effective at preventing COVID-19 in clinical trial participants. Pfizer/BioNTech announced on Nov. 18 that its trial has met all of the required safety and efficacy endpoints and that its two-dose vaccine is 95 percent effective against COVID-19 beginning 28 days after the first dose. (In adults 65 and older, the vaccine was found to be 94 percent effective at preventing COVID-19.) An interim analysis of Moderna’s phase 3 clinical trial found its vaccine to be 94.5 percent effective at preventing COVID-19. It’s important to note, however, that the data from both trials has not been peer-reviewed. 

Pfizer has submitted its coronavirus vaccine to the U.S. Food and Drug Administration (FDA) for emergency use authorization (EUA). The agency is expected to meet with an advisory committee to discuss the vaccine candidate on Dec. 10. Moderna expects to file for EUA in the coming weeks, once it meets all of its safety and efficacy endpoints.

What is emergency use authorization?

An EUA is a green light, of sorts, from the FDA. It is not the same as official approval.

During a public health emergency, such as the coronavirus pandemic, the FDA can authorize previously unapproved medical products to diagnose, treat or prevent the illness of concern in a timely manner when there are no other approved or available alternatives. The EUA process is faster than standard FDA approval, which can take six to 10 months. However, data proving safety and effectiveness are still required for authorization, and the FDA and an advisory committee of experts use this data to weigh the risks and benefits of the product in question.  

What other vaccines hold promise?

The Moderna and Pfizer vaccines are two of four vaccines in the third phase of testing in U.S. trials. The others include one from AstraZeneca and the University of Oxford, and another from Johnson & Johnson.

A phase 3 trial is when researchers study the safety and effectiveness of the vaccine candidates against a placebo in a large population (more than 30,000 volunteers in the case of these vaccine trials). A phase 3 trial also allows researchers to see how well these vaccines work in populations that are most likely to get severely ill from a SARS-CoV-2 infection, including older adults, people with underlying health conditions, and racial and ethnic minorities, who have higher rates of hospitalization and death from COVID-19.

“Because if the vaccine can’t work well in the people who need it the most, then obviously we need a better vaccine or a different strategy,” says Jesse Goodman, M.D., director of Georgetown University’s Center on Medical Product Access, Safety and Stewardship (COMPASS) and former chief scientist at the FDA.

The vaccines from Moderna and Pfizer utilize a new technology, known as mRNA, which introduces a genetic code the body can use to make its own viral protein to induce an immune response. AstraZeneca’s vaccine uses a nonreplicating chimpanzee adenovirus to deliver a SARS-CoV-2 spike protein to stimulate an immune response, and Johnson & Johnson’s one-dose vaccine is made from a genetically modified adenovirus.

Just because these four are leading the pack, however, doesn’t mean the other vaccine candidates out there — all 234, according to the Milken Institute’s vaccine tracker — are out of the race. Eight additional vaccines are also in phase 3 trials around the world, a database maintained by the New York Times shows, and more than 50 others are in phase 1 and 2 studies, some of which employ “more traditional technologies that are used in currently approved vaccines,” Goodman explains.

Can more than one vaccine candidate work and be authorized or approved?

Absolutely. “In fact, it’s highly desirable,” says William Schaffner, M.D., an infectious disease specialist and professor of preventive medicine at the Vanderbilt University School of Medicine, because that would mean “there would be more vaccine manufacturers working to actually produce the vaccine, and so we could more expeditiously try to vaccinate the population in the United States and beyond.”

Kathleen Neuzil, M.D., professor in vaccinology and director of the Center for Vaccine Development and Global Health at the University of Maryland School of Medicine, echoes Schaffner’s sentiment and points to the flu vaccine for comparison: There are multiple formulations on the market, including the injectable high-dose vaccine and the nasal spray vaccine, for example, which are recommended for different populations.

“We really need every person on earth, theoretically, to be able to receive this vaccine. So, to me, [having more than one option] is a positive, because we need so much,” she adds.

When will the other coronavirus vaccines apply for EUA?

It’s hard to pinpoint when a vaccine candidate will be ready to apply for FDA authorization — that all depends on when scientists are able to collect enough data from the phase 3 clinical trials to know whether the vaccine is safe and effective at preventing a coronavirus infection or decreasing its severity in at least 50 percent of vaccine recipients. (The 50 percent efficacy standard was set by the FDA in June. For comparison, the influenza vaccine is between 40 percent and 60 percent effective.)

One thing that could delay the process: the rate at which clinical trial participants get infected. In order for the trials to show that a vaccine candidate works, some participants need to contract the coronavirus out in the community. (They are not being introduced to SARS-CoV-2 in the lab.) “The end point is the number of people who get sick; it’s not a calendar date,” Harvard’s Bloom says.

As Schaffner points out, the population that typically volunteers for clinical trials is the same population that is more likely to adhere to public health guidance put in place to prevent the spread of COVID-19. “They’re usually the type of people who, in the COVID era, are being very careful. They’re social distancing; they’re wearing masks. They don’t go out to restaurants; they haven’t traveled,” he says. “And some of us think that these trials may have to run a little longer than people anticipated for just that reason. Because the volunteers tend to be very careful people.”

An adverse reaction to a vaccine candidate could also slow the process. Both AstraZeneca and Johnson & Johnson paused their phase 3 trials to investigate a participant who may have experienced a complication from the vaccine. (The two companies have since resumed research.) Bloom says while this delays things a little bit, “it proves that the system is working.” Pointing to the trial’s safety measures in place, he adds, “It is exactly what should be done when anybody is sick.”

When will a vaccine be available to the public?

As soon as possible. In a Sept. 16 hearing before a Senate committee, Centers for Disease Control and Prevention (CDC) Director Robert Redfield, M.D., said once the FDA green-lights a vaccine, the government “wants to be in a position to distribute it within 24 hours.”

When the FDA issues an EUA for the vaccine, the CDC’s Advisory Committee on Immunization Practices (ACIP) will quickly hold a public meeting to review the vaccine’s data and then vote on whether to recommend the vaccine. The ACIP will also specify who should receive it, based on the data collected in the trials.

If initial supplies are limited, the ACIP is considering four groups to recommend for early COVID-19 vaccination until there’s enough vaccine for everyone:

  • Health care personnel
  • Workers in essential and critical industries
  • People at high risk for hospitalization or death from COVID-19 due to underlying medical conditions
  • People 65 and older

Experts have made predictions on when the vaccine will be more widely available to the general public. The CDC’s Redfield estimates it will likely take “six to nine months to get the American public vaccinated.”

How will the vaccine be distributed?

The federal government is overseeing the distribution and tracking of coronavirus vaccines in the U.S., and the CDC is working with state, tribal, territorial and local jurisdictions for vaccine plans in their respective areas. The government is also partnering with private companies to ensure high-risk individuals can easily access a vaccine when one is available.

All vaccines will be ordered through the CDC; much of the vaccine manufacturing and stockpiling is happening at the same time as late-stage clinical trials so that if/when a vaccine receives FDA authorization or approval, the medicine will be ready to roll out to the public. 

Ensuring there is proper transportation and storage for the vaccines is part of this planning process. Both the Pfizer and the Moderna vaccines require cold storage at specific temperatures — Pfizer’s more so than Moderna’s — meaning pharmacies and clinics throughout the U.S. will need to be equipped with specialized freezers and refrigerators to keep the medicines stable.

Ordering the supplies needed to vaccinate millions of Americans is another key part of the distribution planning process, as is scaling up safety surveillance and monitoring for long-term effectiveness.

“I think in the beginning, it’s going to be very, very challenging,” Harvard’s Bloom said about the vaccine distribution process. “But by the end of the spring, if not well before then, this should be running smoothly,” pending any technical glitches.

How much will the vaccine cost?

The goal: Nothing. The federal government has prepurchased hundreds of millions of vaccine doses with taxpayer money, and these will be given to Americans at no cost, according to the CDC.

Vaccine providers will be able to charge an administration fee for giving the shot, but this fee should be covered by public or private insurance, or by a government relief fund for the uninsured.

If a vaccine is not 100 percent effective, can I still get COVID-19?

That may be the case, although more details on the vaccine’s effectiveness — especially in subpopulations — should emerge in the third phase of clinical trials and in posttrial surveillance. And “that’s something that the recipients will have to understand when they get the vaccine,” Schaffner says. “The vaccine provides protection, but it won’t be like a suit of armor.”

His main message: Just because you roll up your sleeve and get the shot doesn’t mean you can throw away your mask and disregard other prevention efforts such as social distancing and handwashing. Those will be crucial “for quite some time” in order to get control over the virus, Schaffner says.

Another consideration: An approved vaccine will likely require two doses, several weeks apart, which will stretch out the time before it is effective in recipients. (Johnson & Johnson’s one-dose vaccine candidate is the exception.) The duration of immunity from the vaccine is also unclear at this point. “It’s possible people will need boosters before we’re done with all this,” Goodman adds.

Why does the vaccine development process take so long?

Though timelines may seem long and “frustratingly inefficient,” the speed at which the coronavirus vaccine process is moving is unprecedented, says Duke’s Moody.

Vaccine development typically takes 10 to 15 years, and the fastest vaccine created thus far was for mumps — that process took four years. What’s more, after a vaccine is approved, it can take months to years to scale up manufacturing and production for widespread distribution. The U.S., however, already has a head start on this.

“I think it’s really important for people to understand that the response to this pathogen has been faster than any other pathogen in history,” Moody says. “The fact that you had a virus that was first reported in China in December, and by March we were already talking about setting up a phase 1 trial … I think the speed of the response, both by the medical community and by everyone else, is actually pretty astonishing.”

What if scientists don’t come up with a coronavirus vaccine that works?

That’s unlikely at this point, but it is a possibility. And that’s why it’s important to pursue treatments for COVID-19, as well, Moody says.

“If we had sort of the Tamiflu equivalent for coronavirus where you could be exposed and take Tamiflu and be protected, or you could get early disease and it could attenuate the disease or shorten the course, that would be great,” Moody says of the antiviral treatment for influenza. “There’s a lot of work being done there. And I think all of that work needs to proceed as well.”

The FDA has so far approved the antiviral drug remdesivir for treatment of some patients hospitalized with COVID-19. The agency has also issued an EUA for convalescent plasma to treat people who are hospitalized with the illness and for bamlanivimab, a monoclonal antibody therapy to treat mild to moderate cases of COVID-19 in nonhospitalized patients.

The World Health Organization has also published guidelines that recommend the use of inexpensive and common corticosteroids such as hydrocortisone and dexamethasone for the treatment of patients with severe cases of COVID-19. The guidelines come after an analysis of several clinical trials found that corticosteroids cut the risk of death in patients hospitalized with COVID-19. The new guidelines, however, emphasize that steroids should not be used to treat patients with mild symptoms of the disease.

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