Though many people are pinning their hopes on a COVID-19 vaccine, another option is available: preventive treatment. At a Senate hearing this week, Anthony Fauci noted that a vaccine — which is probably months or years away — isn’t the only way to protect someone from a life-threatening virus.
These treatments could protect people against infection for a few weeks or months, said Fauci, the director of the National Institute of Allergy and Infectious Diseases. While most ongoing research studies are focused on finding treatments for people who are already sick with COVID-19, some researchers are looking to see if they can stop people who are at high risk from getting sick in the first place.
It’s a proven strategy: preventive drugs have been used for decades to help people protect themselves against malaria. More recently, they were a breakthrough in the fight against HIV. There’s no effective vaccine against HIV, but people can take a daily medication that reduces their risk of contracting it through sexual activity by 99 percent. The medication is a pre-exposure prophylactic, or PrEP — a drug used to prevent disease in people who haven’t yet been exposed to it.
“We have an incredibly powerful tool that can, for myself personally, protect me from HIV,” says James Krellenstein, co-founder of the PrEP4All Collaboration and an organizer of a COVID-19 working group in New York.
Krellenstein published a report this week outlining the clinical trials underway to find drugs that can prevent COVID-19. Viruses make people sick when they replicate and spread through the body, and most anti-viral drugs are designed to stop that replication process. Giving someone the drug early, when there’s only a small number of virus particles in the body, is going to be more effective than waiting until the virus is everywhere, Caleb Skipper, an infectious disease postdoctoral fellow at the University of Minnesota, told The Verge. In theory, a drug could be even more effective if it’s already in the body when the first virus appears.
Skipper is part of a research team at the University of Minnesota running a clinical trial to see if hydroxychloroquine, which can stop the coronavirus from replicating in a test tube, can help keep health care workers from catching COVID-19. The drug has been the subject of a lot of controversy and hasn’t been able to effectively treat people who are already sick and hospitalized.
Ongoing enrollment for Pre-exposure prophylaxis (PrEP) trial for high risk healthcare workers and first responders anywhere in the US (and parts of Canada soon). https://t.co/zDhgb307LQ #MedTwitter pic.twitter.com/s5ZFXA7JqL— David Boulware, MD MPH (@boulware_dr) May 5, 2020
The majority of clinical trials looking at preventive drugs now are testing hydroxychloroquine, Krellenstein found. He argues that research into prophylactics needs to cast a wider net and look at other candidates, too. “Vaccines are much an art as a science, and there’s a lot of hit and miss. It would be substantial if we could identify a molecular compound that could really inhibit COVID-19 acquisition,” he says.
Some researchers are looking outside of hydroxychloroquine. At Johns Hopkins, researchers are testing to see if convalescent plasma, the antibody-rich blood of COVID-19 survivors, could be protective. A trial testing how well it protects people who have been exposed to the novel coronavirus from becoming sick will start enrolling participants next week.
“You could imagine everyone in a meatpacking plant could get this. You could imagine everyone in the White House could get this, people at high risk,” says David Sullivan, professor of molecular microbiology and immunology at the Johns Hopkins Malaria Research Institute, who’s involved in the plasma research. “It’s a way for those critical people to get immediate immunity.”
The trial will test if the plasma confers protection, and if it does, how long it might last. “Plasma is a single dose — you could go in and get it once and have protection for a month, or six weeks,” Sullivan says. “We think that this is one of the essential steps to returning us to a functioning society. But we have to demonstrate that it works.”
If plasma helps prevent COVID-19, it could be a sign that more refined antibody treatments might also be useful as protection, he says. Pharmaceutical companies are trying to identify the antibodies that are most effective at blocking the novel coronavirus. Then, they’d be able to produce a more targeted cocktail of virus-blocking substances than plasma, which is a general mix of all the antibodies a sick person’s body creates. “Convalescent plasma is the first step towards other products,” Sullivan says.
Both plasma and antibodies typically require IV infusions, so the logistics of providing them to people at risk of contracting COVID-19 is challenging — although it may only need to be given once to confer some level of protection. Hydroxychloroquine is a pill, so it’s simpler for people to take, but may have to be taken daily.
Sullivan thinks that the limitations aren’t insurmountable. And identifying drugs that can protect people from the novel coronavirus is a critical step toward controlling the pandemic, he says.
“It’s all hands on deck treating people who are sick. That has to be done,” Sullivan says. But the best way to help people is to keep them from getting sick in the first place. It could also help them feel safer leaving the house. “If I have a treatment that shortens hospitalization, I’m still going to worry about going out and about, if it means I might have to go to the hospital,” he says.
Treatments are important, Sullivan says, but they help put out fires that are already raging. “Prophylaxis is like throwing water on a box of matches,” he says. “Wet matches aren’t going to light in the first place.”