Dec. 10, 2020 -- There is light at the end of the tunnel.

That is the new mantra of infectious disease specialist Anthony Fauci, MD, director of the National Institute of Allergy and Infectious Diseases, and other public health experts as COVID-19 cases climb at alarming rates in the U.S.

The vaccine -- or actually vaccines -- are coming. Today, the FDA will consider Pfizer/BioNTech's request for an emergency use authorization (EUA) for its vaccine. It will review Moderna's request Dec. 17. And AstraZeneca and the University of Oxford have also released data on their phase III vaccine trials and may be next to seek an EUA.

How These 'Front-Runner' Vaccines Work

The vaccines from Moderna and Pfizer require two doses. They use a new approach, messenger RNA or mRNA, that has not yet been used in any other commercial vaccine. Rather than inject an inactivated or weakened virus, as some vaccines do, these vaccines work by teaching the immune system how to make a protein or piece of a protein that triggers an immune response. The body produces antibodies, protecting it when the actual virus shows up.

The AstraZeneca/University of Oxford vaccine uses a genetically altered, weakened version of a common cold vaccine taken from chimpanzees. It contains the genetic material of the SARS-CoV-2 virus spike protein. After vaccination, the spike protein is produced, preparing the immune system to attack the virus if it later infects the person.

What the Data Shows So Far

All three companies have released interim results of their phase III studies, which are designed to evaluate safety and efficacy. Overall, Pfizer and Moderna say their vaccines are about 95% effective; AstraZeneca's vaccine is 70% effective.

The phase III trials for each enrolled, or plan to enroll, up to 30,000 or more volunteers.

"The issue isn't really efficacy [alone]," says Naor Bar-Zeev, PhD, an associate professor of international health and vaccinology and deputy director of the International Vaccine Access Center at Johns Hopkins Bloomberg School of Public Health. It's also about how long that protection lasts. He says a vaccine with lower effectiveness but a longer protection time would be preferable to a vaccine with a higher effectiveness but less protection time.

The FDA has said that to get emergency use authorization, any vaccine candidate must be at least 50% effective. That means a vaccine would prevent disease or make it less severe in at least 50% of the people vaccinated before the FDA would grant authorization.

What We All Want to Know

How long will the vaccines protect against COVID? That's impossible to say right now, as the phase III volunteers have been followed for only a few months, says Paul Offit, MD, director of the Vaccine Education Center and a professor of pediatrics at Children's Hospital of Philadelphia. But vaccine experts can make an educated guess. Based on other viruses that are similar to the one causing COVID-19 in terms of mutation and other things, Offit says the COVID-19 vaccines that are highly effective might protect people for a few years.

How soon after the vaccine is given is the body protected? "From about a week after the second dose.," Bar-Zeev says.

What about side effects? And how safe are the vaccines? At a meeting with the CDC, doctors recently warned about common and transient side effects just after getting the vaccine, such as arm soreness, fatigue, body aches, and perhaps even fever.

But people hesitant to get the vaccine often worry about serious side effects. "Phase III [research] is not enough to tell us about rare side effects," Bar-Zeev says. But “that doesn't mean you shouldn't take the vaccine."

At least two people who received the Pfizer vaccine on the first day of inoculations in the United Kingdom this week had severe allergic reactions. The effects prompted the British government to recommend that anyone prone to severe allergic reactions not take the vaccine.

Phase III trials do offer some information about less common side effects, Offit says, beyond the common ones of arm soreness and fatigue. For instance, Moderna analyzed some safety data and found that fatigue was reported by almost 10% of people, and headache by about half that, or 4.5%.

And, “in a very short period of time, you are going to know if there is a very rare side effect," after the vaccine distribution begins and more people get the shot, Offit says.

Will safety be tracked after a vaccine gets the FDA's authorization?

Yes. After an EUA is given, more assessments take place, according to the CDC. The goal is to understand more about how the vaccine works in “real-world” conditions. Among other goals, these assessments help provide information about groups of people that may not have been well-represented in the clinical trials.

Will the vaccines not only prevent sickness in the person vaccinated, but also prevent transmission of the virus to others?

That is not yet known, Offit and Bar-Zeev agree. As more data is available, researchers will be able to say if a vaccinated person, if exposed to the virus, can still spread it even if they don't get sick from the virus. "If the vaccines only reduce disease, it's even more important to have uptake of the vaccine [in the population]," Bar-Zeev says.

But Offit says that even if someone who has been vaccinated remains contagious, “I still think we can bring this virus down [with vaccinations].”

When will we get vaccinated? That depends on a number of things, including age, medical risks, and living and working arrangements. Experts from the Advisory Committee on Immunization Practices, which advises the CDC, have suggested that health care providers and residents of long-term care facilities get the vaccine first.

Those groups will likely be followed by essential workers, adults with serious medical conditions, and people over 65.

By May or June, the “ordinary citizen” should be able to get it, Fauci told Good Morning America in mid-November.

How long do I wait between doses? The second dose of the Pfizer vaccine comes 21 days after the first. People getting the Moderna vaccine wait 28 days between doses.

Will the vaccines be free? They will be free for those receiving the vaccine, although providers will bill insurance companies, Medicaid and Medicare, or tap federal funds for the uninsured. In one estimate, the per-dose cost of the Moderna vaccine was $37, while Pfizer's was $20 and AstraZeneca's was $4.


When the vaccines are available, should you choose one over another, if given a choice? "In general, it doesn't matter which vaccine you get because [once given an EUA by the FDA], they all work," Bar-Zeev says. "We're spoiled for choice."

Can you "mix and match" vaccines that need two doses (such as the Moderna and Pfizer vaccines)? No. These two vaccines use the same general approach but are different. "Stay with the same vaccine for dose one and two," Bar-Zeev says.

What about “vaccine hesitancy,” the people who say they will wait to get vaccinated, aren’t sure, or say they will decline?

"I think this will be a desired vaccine," Offit says, despite some recent polls that show relatively high percentages of people aren't yet sure about getting one.

In a poll taken by the American Nurses Foundation in October, 36% of the nearly 13,000 nurses who responded said they would not take the vaccine voluntarily if their employer did not require it. Another 34% said they would, and the rest were not sure.

Vaccine safety is never an absolute, experts know. In deciding whether to get vaccinated, "the issue is not to be certain, but to make a wise decision in the face of uncertainty," Bar-Zeev says.

The risk must be balanced with the benefit, he says, such as taking into account one's risk factors -- including age and medical conditions, as well as the status of COVID-19 spread in the community. So an older person in a community with a high number of cases might make a very different decision than a younger person in good health in a community with few cases, he says.

WebMD Health News


Paul Offit, MD, director, Vaccine Education Center, and professor of pediatrics, Children's Hospital of Philadelphia; professor of vaccinology, Perelman School of Medicine, University of Pennsylvania.

Naor Bar-Zeev, PhD, associate professor of international health and vaccinology and deputy director, International Vaccine Access Center, Johns Hopkins Bloomberg School of Public Health, Baltimore.

JAMA Live Stream: Dec. 2, 2020.

American Nurses Foundation: "Pulse of the Nation's Nurses COVID-19 Survey Series: COVID-19 Vaccine."

CDC: "Understanding How COVID-19 Vaccines Work," "Ensuring COVID-19 Vaccines Work," "Meeting of the Advisory Committee on Immunization Practices (ACIP) November 23."

CDC, ACIP COVID-19 Work Group: "Phased Allocation of COVID-19 Vaccines." "The Cost Per Jab of Covid-19 Vaccine Candidates."

FDA: "Coronavirus (COVID-19) Update: FDA Takes Action to Help Facilitate Timely Development of Safe, Effective COVID-19 Vaccines."

AstraZeneca: "COVID-19 vaccine AZD1222 is better tolerated in older adults than younger adults with similar immune responses across all age groups," "AZD1222 vaccine met primary efficacy endpoint in preventing COVID-19."

The Lancet: "Safety and immunogenicity of ChAdOx1nCoV-19 in a prime-boost regimen in young and old adults (COV002) in a single-blind, randomized, controlled, phase 2/3 trial."

Good Morning America: Interview with Anthony Fauci, MD.

Pfizer: "Pfizer and BioNtech Conclude Phase 3 Study of COVID-19 Vaccine Candidate, Meeting All Primary Efficacy Endpoints."

Moderna: "Moderna's COVID-19 Vaccine Candidate Meets its Primary Efficacy Endpoint in the First Interim Analysis of the Phase 3 COVE Study." "Covid-19: Moderna vaccine is nearly 95% effective, trial involving high risk and elderly people shows." 

USA Today: “Are there side effects to a COVID-19 vaccine? What are the 'ingredients'? The cost? Answers to your vaccine questions.”

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