Several companies are developing or testing antivirals against SARS-CoV-2, the virus that causes COVID-19.

Antivirals target the virus in people who already have an infection. They work in different ways, sometimes preventing the virus from replicating, other times blocking it from infecting cells.

Lee says antivirals work better if you administer them sooner, “before the virus has a chance to multiply significantly.”

And also before the virus has caused significant damage to the body, such as to the lungs or other tissues.

Dr. Robert Amler, dean of the School of Health Sciences and Practice at New York Medical College and a former chief medical officer at the Centers for Disease Control and Prevention (CDC) Agency for Toxic Substances and Disease Registry (ATSDR), says both antivirals and vaccines will be valuable tools in combating COVID-19.

However, he told Healthline that “antivirals are likely to be developed and approved before a vaccine, which typically takes longer.”

Drug development is sometimes described as a pipeline with compounds moving from early laboratory development to laboratory and animal testing to clinical trials in people.

It can take a decade or more for a new compound to go from initial discovery to the marketplace. Many compounds never even make it that far.

That’s why antivirals being eyed as treatments for COVID-19 are drugs that already exist.



Developed a decade ago, this drug failed in clinical trials against Ebola in 2014. But it was found to be generally safe in people. Research with MERS showed that the drug blocked the virus from replicating.

In April, it was being tested in five COVID-19 clinical trialsTrusted Source. The first results weren’t encouraging. In mid-April, the Department of Veterans Affairs reported that the drug produced no noticeable benefits in patients at veterans’ hospitals. They also noted that the death rate among this group was higher than among patients who were given standard medical care.

In late April, Gilead Sciences announced one of its trials had been “terminated” due to low enrollment. Gilead officials said the results of that trial had been “inconclusive” when it was ended.

A few days later, they company announced that another trial of remdesivir overseen by the National Institute of Allergy and Infectious Diseases had “met its primary endpoint.”

Dr. Anthony FauciTrusted Source, the institute’s director, told reporters the trial produced a “clear cut positive effect in diminishing time to recover.” He said people taking the drug recovered from COVID-19 in 11 days compared to 15 days to people who didn’t take remdesivir. More details will be released after the trial is peer reviewed and published.

At the same time, another studyTrusted Source published in The Lancet, reported that participants in a clinical trial who took remdesivir showed no benefits compared to people who took a placebo.

Despite the conflicting results, the FDA issued an orderTrusted Source on May 1 for the emergency use of remdesivir.


This is a combination of two drugs that work against HIV. Clinical trials are planned to see whether it works against SARS-CoV-2.


This drug is approved in some countries outside the United States to treat influenza. Some reports from China suggest it may work as a treatment for COVID-19. These results, though, haven’t been published yet.


This antiviral was tested along with the drug lopinavir/ritonavir as a treatment for COVID-19. Researchers reported in mid-April that the two drugs didn’t improve the clinical outcomes for people hospitalized with mild to moderate cases of COVID-19.

Other drugs

Scientists are also looking at other ways to target the virus or treat the complications of COVID-19, such as:

Monoclonal antibodies

These drugs trigger the immune system to attack the virus. Vir Biotechnology has isolated antibodies from patients who survived SARS.

The company is working with Chinese firm WuXi Biologics to test them as a treatment for COVID-19. AbCellera has isolated 500 unique antibodies from a person who recovered from COVID-19 and is set to start testing them.

Blood plasma transfers

Along the same lines, the FDA has announcedTrusted Source a process for medical facilities to conduct trials on an experimental treatment that uses blood plasma from people who have recovered from COVID-19.

The theory is that the plasma contains antibodies that will attack this particular coronavirus. In late March, the New York Blood Center began collecting plasma from people who have recovered from COVID-19.

Stem cells

Athersys Inc. released preliminary data last year showing that its stem cell treatment could potentially benefit people with acute respiratory distress syndrome (ARDS).

This condition occurs in some people with severe COVID-19. MesoblastTrusted Source tested its stem cell product in a small group of people with COVID-19 with positive results.

Immune suppressants

In some people with COVID-19, the immune system goes into overdrive, releasing large amounts of small proteins called cytokines. Scientists think this “cytokine storm” may be the reason certain people develop ARDS and need to be put on a ventilator.

Several immune suppressants are being tested in clinical trials to see whether the drugs can quell the cytokine storm and reduce the severity of ARDS.

These include baricitinib, a drug for rheumatoid arthritis; CM4620-IE, a drug for pancreatic cancer; and IL-6 inhibitors. The FDA has also approved a device that filters cytokinesTrusted Source out of the blood of patients.

Next steps

While a lot of the focus is on developing new treatments for COVID-19, improvements in how doctors care for patients using existing technology are also crucial.

“The things that we have to worry about with the novel coronavirus is that it can cause pneumonia and acute respiratory distress syndrome,” Lee said. “There are ways of treating those things that can reduce the effects, so doctors are trying to use those as well.”

No company has offered a timeline for when its drug might be used more widely to treat COVID-19. This isn’t an easy thing to estimate.

After laboratory and animal testing, drugs have to pass through several clinical trial stagesTrusted Source before they can be approved for widespread use in people.

It’s also difficult to speed things up, because scientists have to enroll enough people in each stage to have useful results. They also have to wait long enough to see whether there are harmful side effects of the drug.

However, drugs can sometimes be given to people outside a clinical trial through the FDA’s “compassionate useTrusted Source” program. For this to happen, people must have an “immediately life-threatening condition or serious disease or condition.”

Doctors at the University of California, Davis were able to secure this type of approval for a woman with severe COVID-19 to receive remdesivir. They report she’s now doing well.

Many will take this as a sign that the drug works. But because the drug was given outside of a clinical trial to just one person, it’s not possible to know for certain. Also, other people may not have the same response to the drug.

Clinical trial stages
  • Phase I. The drug is given to a small number of healthy people and people with a disease to look for side effects and figure out the best dose.
  • Phase II. The drug is given to several hundred people who have the disease, looking to see whether it works and if there are any side effects that weren’t caught during the initial testing.
  • Phase III. In this large-scale trial, the drug is given to several hundred or even up to 3,000 people. A similar group of people take a placebo, or inactive compound. The trial is usually randomized and can take 1 to 4 years. This stage provides the best evidence of how the drug works and the most common side effects.
  • Phase IV. Drugs that are approved for use undergo continued monitoring to make sure there are no other side effects, especially serious or long-term ones.


A vaccine is designed to protect people before they’re exposed to a virus — in this case, SARS-CoV-2, the virus that causes COVID-19.

A vaccine basically trains the immune systemTrusted Source to recognize and attack the virus when it encounters it.

Vaccines protect both the person who’s vaccinated and the community. Viruses can’t infect people who are vaccinated, which means vaccinated people can’t pass the virus to others. This is known as herd immunity.

Many groupsTrusted Source are working on potential vaccines for SARS-CoV-2, with several backed by the nonprofit Coalition for Epidemic Preparedness Innovations (CEPI).

There are 120 projects around the world centered on the development of a vaccine. Five had been approved for clinical trials on people.

Here’s a look at some of the projects:

  • Moderna. In March, the company began testing its messenger RNA (mRNA) vaccine in a phase I clinical trial in Seattle, Washington. The study includes 45 healthy volunteers, ages 18 to 55, who are getting two shots 28 days apart. The company has developed other mRNA vaccines before. Those earlier studies showed that their platform is safe, which allowed the company to skip certain animal testing for this specific vaccine.
  • Inovio. When COVID-19 appeared in December, the company had already been working on a DNA vaccine for MERS, which is caused by another coronavirus. This allowed the company to quickly develop a potential vaccine for SARS-Cov-2. Company officials said they expect to have all 40 volunteers signed up for their initial clinical trial by the end of April.
  • University of Queensland in Australia. Researchers are developing a vaccine by growing viral proteins in cell cultures. They began preclinical testing stages in early April.
  • University of Oxford in England. A clinical trial with more than 500 participants began in late April. Oxford officials said the potential vaccine has an 80 percent chance for success and could be available as early as September. The vaccine uses a modified virus to trigger the immune system.
  • Pharmaceutical companies. Johnson & Johnson and Sanofi are both working on a vaccine of their own. Pfizer has also teamed up with a German company to develop a vaccine. Their initial clinical trial with 200 participants was given the green light in late April.

Advances in genetic sequencing and other technological developments have sped up some of the earlier laboratory work for vaccine development.

However, Dr. Anthony FauciTrusted Source, director of the National Institute of Allergy and Infectious Diseases, told reporters in March that a vaccine won’t be available for widespread use for at least another 12 to 18 months.

This is the timeline to complete the phase III clinical studies.

Meanwhile, some clinical trials are underway in the Netherlands and Australia to see whether existing vaccines for tuberculosis might also protect against SARS-CoV-2.

The polio vaccine is another possible option. Scientists think these vaccines might boost the immune system just enough to fight off the new coronavirus, although there’s no evidence yet to confirm this theory.

There’s no guarantee any of the vaccine candidates will work.

“There’s a lot of uncertainty with vaccine development,” Lee said. “Naturally, you have to make sure the vaccine is safe. But you also have to make sure the vaccine will elicit enough of an immune response.”

Like drugs, potential vaccines have to pass through the same clinical trial stagesTrusted Source. This is especially important when it comes to safety, even during a pandemic.

“The public’s willingness to back quarantines and other public-health measures to slow spread tends to correlate with how much people trust the government’s health advice,” Shibo Jiang, a virologist at Fudan University in China, wrote in the journal NatureTrusted Source.

“A rush into potentially risky vaccines and therapies will betray that trust and discourage work to develop better assessments,” he said.