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Early Data Suggest Pfizer Pill May Prevent Severe COVID-19

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Woman holding a pill bottle. Chemical molecular structure is nearby
Credit: Fizkes/Shutterstock

Over the course of this pandemic, significant progress has been made in treating COVID-19 and helping to save lives. That progress includes the development of life-preserving monoclonal antibody infusions and repurposing existing drugs, to which NIH’s Accelerating COVID-19 Therapeutic Interventions and Vaccines (ACTIV) public-private partnership has made a major contribution.

But for many months we’ve had hopes that a safe and effective oral medicine could be developed that would reduce the risk of severe illness for individuals just diagnosed with COVID-19. The first indication that those hopes might be realized came from the announcement just a month ago of a 50 percent reduction in hospitalizations from the Merck and Ridgeback drug molnupiravir (originally developed with an NIH grant to Emory University, Atlanta). Now comes word of a second drug with potentially even higher efficacy: an antiviral pill from Pfizer Inc. that targets a different step in the life cycle of SARS-CoV-2, the novel coronavirus that causes COVID-19.

The most recent exciting news started to roll out earlier this month when a Pfizer research team published in the journal Science some promising initial data involving the antiviral pill and its active compound [1]. Then came even bigger news a few days later when Pfizer announced interim results from a large phase 2/3 clinical trial. It found that, when taken within three days of developing symptoms of COVID-19, the pill reduced by 89 percent the risk of hospitalization or death in adults at high risk of progressing to severe illness [2].

At the recommendation of the clinical trial’s independent data monitoring committee and in consultation with the U.S. Food and Drug Administration (FDA), Pfizer has now halted the study based on the strength of the interim findings. Pfizer plans to submit the data to the FDA for Emergency Use Authorization (EUA) very soon.

Pfizer’s antiviral pill is a protease inhibitor, originally called PF-07321332, or just 332 for short. A protease is an enzyme that cleaves a protein at a specific series of amino acids. The SARS-CoV-2 virus encodes its own protease to help process a large virally-encoded polyprotein into smaller segments that it needs for its life cycle; a protease inhibitor drug can stop that from happening. If the term protease inhibitor rings a bell, that’s because drugs that work in this way already are in use to treat other viruses, including human immunodeficiency virus (HIV) and hepatitis C virus.

In the case of 332, it targets a protease called Mpro, also called the 3CL protease, coded for by SARS-CoV-2. The virus uses this enzyme to snip some longer viral proteins into shorter segments for use in replication. With Mpro out of action, the coronavirus can’t make more of itself to infect other cells.

What’s nice about this therapeutic approach is that mutations to SARS-CoV-2’s surface structures, such as the spike protein, should not affect a protease inhibitor’s effectiveness. The drug targets a highly conserved, but essential, viral enzyme. In fact, Pfizer originally synthesized and pre-clinically evaluated protease inhibitors years ago as a potential treatment for severe acute respiratory syndrome (SARS), which is caused by a coronavirus closely related to SARS-CoV-2. This drug might even have efficacy against other coronaviruses that cause the common cold.

In the study published earlier this month in Science [1], the Pfizer team led by Dafydd Owen, Pfizer Worldwide Research, Cambridge, MA, reported that the latest version of their Mpro inhibitor showed potent antiviral activity in laboratory tests against not just SARS-CoV-2, but all of the coronaviruses they tested that are known to infect people. Further study in human cells and mouse models of SARS-CoV-2 infection suggested that the treatment might work to limit infection and reduce damage to lung tissue.

In the paper in Science, Owen and colleagues also reported the results of a phase 1 clinical trial with six healthy people. They found that their protease inhibitor, when taken orally, was safe and could reach concentrations in the bloodstream that should be sufficient to help combat the virus.

But would it work to treat COVID-19 in an infected person? So far, the preliminary results from the larger clinical trial of the drug candidate, now known as PAXLOVID™, certainly look encouraging. PAXLOVID™ is a formulation that combines the new protease inhibitor with a low dose of an existing drug called ritonavir, which slows the metabolism of some protease inhibitors and thereby keeps them active in the body for longer periods of time.

The phase 2/3 clinical trial included about 1,200 adults from the United States and around the world who had enrolled in the clinical trial. To be eligible, study participants had to have a confirmed diagnosis of COVID-19 within a five-day period along with mild-to-moderate symptoms of illness. They also required at least one characteristic or condition associated with an increased risk for developing severe illness from COVID-19. Each individual in the study was randomly selected to receive either the experimental antiviral or a placebo every 12 hours for five days.

In people treated within three days of developing COVID-19 symptoms, the Pfizer announcement reports that 0.8 percent (3 of 389) of those who received PAXLOVID™ were hospitalized within 28 days compared to 7 percent (27 of 385) of those who got the placebo. Similarly encouraging results were observed in those who got the treatment within five days of developing symptoms. One percent (6 of 607) on the antiviral were hospitalized versus 6.7 percent (41 of 612) in the placebo group. Overall, there were no deaths among people taking PAXLOVID™; 10 people in the placebo group (1.6 percent) subsequently died.

If all goes well with the FDA review, the hope is that PAXLOVID™ could be prescribed as an at-home treatment to prevent severe illness, hospitalization, and deaths. Pfizer also has launched two additional trials of the same drug candidate: one in people with COVID-19 who are at standard risk for developing severe illness and another evaluating its ability to prevent infection in adults exposed to the coronavirus by a household member.

Meanwhile, Britain recently approved the other recently developed antiviral molnupiravir, which slows viral replication in a different way by blocking its ability to copy its RNA genome accurately. The FDA will meet on November 30 to discuss Merck and Ridgeback’s request for an EUA for molnupiravir to treat mild-to-moderate COVID-19 in infected adults at high risk for severe illness [3]. With Thanksgiving and the winter holidays fast approaching, these two promising antiviral drugs are certainly more reasons to be grateful this year.

References:

[1] An oral SARS-CoV-2 M(pro) inhibitor clinical candidate for the treatment of COVID-19.
Owen DR, Allerton CMN, Anderson AS, Wei L, Yang Q, Zhu Y, et al. Science. 2021 Nov 2: eabl4784.

[2] Pfizer’s novel COVID-19 oral antiviral treatment candidate reduced risk of hospitalization or death by 89% in interim analysis of phase 2/3 EPIC-HR Study. Pfizer. November 5, 2021.

[3] FDA to hold advisory committee meeting to Discuss Merck and Ridgeback’s EUA Application for COVID-19 oral treatment. Food and Drug Administration. October 14, 2021.

Links:

COVID-19 Research (NIH)

Accelerating COVID-19 Therapeutic Interventions and Vaccines (ACTIV) (NIH)

A Study of PF-07321332/Ritonavir in Nonhospitalized Low-Risk Adult Participants With COVID-19 (ClinicalTrials.gov)

A Post-Exposure Prophylaxis Study of PF-07321332/Ritonavir in Adult Household Contacts of an Individual With Symptomatic COVID-19 (ClinicalTrials.gov)


Partnership to Expand Effective Gene Therapies for Rare Diseases

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DNA strands in adenovirus shells. Silhouettes of children are on the right.

Rare diseases aren’t so rare. Collectively, up to 30 million Americans, many of them children, are born with one of the approximately 7,000 known rare diseases. Most of these millions of people also share a common genetic feature: their diseases are caused by an alteration in a single gene.

Many of these alterations could theoretically be targeted with therapies designed to correct or replace the faulty gene. But there have been significant obstacles in realizing this dream. The science of gene therapy has been making real progress, but pursuing promising approaches all the way to clinical trials and gaining approval from the U.S. Food and Drug Administration (FDA) is still very difficult. Another challenge is economic: for the rarest of these conditions (which is most of them), the market is so small that most companies have no financial incentive to pursue them.

To overcome these obstacles and provide hope for those with rare diseases, we need a new way of doing things. One way to do things differently—and more efficiently—is the recently launched Bespoke Gene Therapy Consortium (BGTC). It is a bold partnership of NIH, the FDA, 10 pharmaceutical companies, several non-profit organizations, and the Foundation for the National Institutes of Health [1]. Its aim: optimize the gene therapy development process and help fill the significant unmet medical needs of people with rare diseases.

The BGTC, which is also part of NIH’s Accelerating Medicines Partnership® (AMP®), will enable the easier, faster, and cheaper pursuit of “bespoke” gene therapies, meaning made for a particular customer or user. The goal of the Consortium is to reduce the cost of gene therapy protocols and increase the likelihood of success, making it more attractive for companies to invest in rare diseases and bring treatments to patients who desperately need them.

Fortunately, there is already some precedent. The BGTC effort builds on a pilot project led by NIH’s National Center for Advancing Translational Sciences (NCATS) known as Platform Vector Gene Therapy (PaVe-GT). This pilot project has helped to develop adeno-associated viruses (AAVs), which are small benign viruses engineered in the lab to carry a therapeutic gene. They are commonly used in gene therapy-related clinical trials of rare diseases.

Since the launch of PaVe-GT two years ago, the project has helped to introduce greater efficiency to gene therapy trials for rare disease. It’s also offered a way to get around the standard one-disease-at-a-time approach to therapeutic development that has stymied progress in treating rare conditions.

The BGTC will now continue to advance in-depth understanding of basic AAV biology and develop better gene therapies for rare and also common diseases. The consortium aims to develop a standard set of analytic tests to improve the production and functional assessment of AAVs and therapeutic genes. Such tests will be broadly applicable and will bring the needed manufacturing efficiency required for developing gene therapies for very rare conditions.

The BGTC also will work toward bringing therapies sooner to individuals in need. To start, BGTC-funded research will support four to six clinical trials, each focused on a distinct rare disease. While the details haven’t yet been decided, these diseases are expected to be rare, single-gene diseases that lack gene therapies or commercial programs in development, despite having substantial groundwork in place to enable the rapid initiation of preclinical and clinical studies.

Through these trials, the BGTC will chart a path from studies in animal models of disease to human clinical trials that cuts years off the development process. This will include exploring methods to streamline regulatory requirements and processes for FDA approval of safe and effective gene therapies, including developing standardized approaches to preclinical testing.

This work promises to be a significant investment in helping people with rare diseases. The NIH and private partners will contribute approximately $76 million over five years to support BGTC-funded projects. This includes about $39.5 million from the participating NIH institutes and centers, pending availability of funds. The NCATS, which is NIH’s lead for BGTC, is expected to contribute approximately $8 million over five years.

Today, only two rare inherited conditions have FDA-approved gene therapies. The hope is this investment will raise that number and ultimately reduce the many significant challenges, including health care costs, faced by families that have a loved one with a rare disease. In fact, a recent study found that health care costs for people with a rare disease are three to five times greater than those for people without a rare disease [2]. These families need help, and BGTC offers an encouraging new way forward for them.

References:

[1] NIH, FDA and 15 private organizations join forces to increase effective gene therapies for rare diseases. NIH news release, October 27, 2021.

[2] The IDeaS initiative: pilot study to assess the impact of rare diseases on patients and healthcare systems. Tisdale, A., Cutillo, C.M., Nathan, R. et al. Orphanet J Rare Dis 16, 429 (2021).

Links:

FAQ About Rare Diseases (National Center for Advancing Translational Sciences/NIH)

Bespoke Gene Therapy Consortium (BGTC)

Platform Vector Gene Therapy (NCATS)

Accelerating Medicines Partnership® (AMP®) (NIH)

NIH Support: National Center for Advancing Translational Sciences; Eunice Kennedy Shriver National Institute of Child Health and Human Development; National Eye Institute; National Heart, Lung, and Blood Institute; National Human Genome Research Institute; National Institute of Arthritis and Musculoskeletal and Skin Diseases; National Institute of Dental and Craniofacial Research; National Institute of Mental Health; National Institute of Neurological Disorders and Stroke; National Institute on Deafness and Other Communication Disorders; and NIH’s BRAIN Initiative.


The Latest on COVID-19 Boosters

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COVID-19 Vaccine vials labeled dose one, dose two, and booster

More than 180 million Americans, including more than 80 percent of people over age 65, are fully vaccinated against the SARS-CoV-2 virus responsible for COVID-19. There’s no question that full vaccination is the best way to protect yourself against this devastating virus and reduce your chances of developing severe or long-lasting illness if you do get sick. But, to stay ahead of this terrible virus, important questions do remain. A big one right now is: How soon will booster shots be needed and for whom?

The answers to this question will continue to evolve as more high-quality data become available. But here’s what we know right now for the Pfizer-BioNTech booster. Late last week, Dr. Rochelle Walensky, the Director of the Centers for Disease Control and Prevention (CDC), recommended that:

  • Those 65 years and older and residents in long-term care settings should receive a booster shot at least 6 months after being fully vaccinated with the Pfizer-BioNTech vaccine,
  • People aged 50–64 years with underlying medical conditions should receive a booster shot at least 6 months after being fully vaccinated with the Pfizer-BioNTech vaccine,
  • Individuals aged 18–49 years with underlying medical conditions may receive a booster shot at least 6 months after getting fully vaccinated with their Pfizer-BioNTech vaccine, based on their individual benefits and risks.
  • Frontline workers who received the Pfizer-BioNTech vaccine may receive a booster. This group includes anyone age 18 through 64 whose frequent institutional or occupational exposure to SARS-CoV-2 puts them at high risk of COVID-19. [1]

Taken together, these CDC recommendations are in line with those issued two days earlier by the Food and Drug Administration (FDA) [2].

Some of the most-compelling data that was under review came from an Israeli study, published recently in the New England Journal of Medicine, that explored the benefit of booster shots for older people [3]. Israel, with a population of around 9 million, has a national health system and one of the world’s highest COVID-19 vaccination rates. That country’s vaccination campaign, based solely on Pfizer-BioNTech, was organized early in 2021, and so its experience is about three months ahead of ours here in the U.S. These features, plus some of the world’s largest integrated health record databases, have made Israel an important source of early data on how the Pfizer-BioNTech mRNA vaccine can be expected to work in the real world over time.

Earlier this year, Israeli public health officials noted evidence for an increased number of breakthrough infections, some of which were severe. So, at the end of July 2021, Israel approved the administration of third doses, or “boosters,” of the Pfizer-BioNTech vaccine for people ages 60 and up who had received their second dose at least five months before.

To find out how well these booster shots worked to bolster immune protection against COVID-19, researchers looked to more than 1.1 million fully vaccinated people who were at least 60 years old. They compared the rate of confirmed COVID-19 infection and severe illness from the end of July to the end of August among people who’d received a booster at least 12 days earlier with those who hadn’t gotten boosters.

Nearly 13,500 older individuals who’d been fully vaccinated before March 2021, got a breakthrough infection during the two months of study. Importantly, the rate of confirmed infection in the group that got boosters was 10 times lower on average than in the group that didn’t get boosters. The data on severe illness looked even better. Of course, there could be other factors at play that weren’t accounted for in the study, but the findings certainly suggest that a third Pfizer shot is safe and effective for older people.

Though the Israeli studies on booster shots are a little ahead of the international pack, we are starting to see results from the research underway in the U.S. Last week, for example, Johnson & Johnson announced new data in support of boosters to improve and extend immune protection in those who received its single-dose COVID-19 vaccine [4]. For people who received the Moderna mRNA vaccine, the company has already submitted its data to the FDA for booster authorization. A decision is expected soon.

As the critical evidence on boosters continues to emerge, the most important way to avoid another winter surge of COVID-19 is to follow all public health recommendations. Most importantly, that includes getting fully vaccinated if you haven’t already, and encouraging others around you to do the same. If you’re currently eligible for a booster shot, they are available at 80,000 locations across the nation, and can help you stay healthy and well for the coming holiday season.

For others eager to do everything possible to protect themselves, their families, and their communities against this terrible virus—but who are not yet eligible for a booster—sit tight for now. The data on booster shots are still coming in for folks like me who were immunized with the Moderna or Johnson & Johnson vaccines. It’s likely that the FDA and CDC will widen their recommendations in the coming weeks.

In the meantime, the Delta variant is still out there and circulating. That makes it critical to maintain vigilance. Wear a mask in indoor spaces, keep a physical distance from others, and remember to wash your hands frequently. We are all really tired of COVID-19, but patience is still required as we learn more about how best to stay ahead of this virus.

References:

[1] CDC statement on ACIP booster recommendations. Centers for Disease Control and Prevention news release. September 24, 2021

[2] FDA authorizes booster dose of Pfizer-BioNTech COVID-19 vaccine for certain populations. Food and Drug Administration news release. September 22, 2021

[3] Protection of BNT162b2 vaccine booster against Covid-19 in Israel. Bar-On YM, Goldberg Y, Mandel M, Bodenheimer O, Freedman L, Kalkstein N, Mizrahi B, Alroy-Preis S, Ash N, Milo R, Huppert A. N Engl J Med. 2021 Sep 15.

[4] Johnson & Johnson announces real-world evidence and Phase 3 data confirming strong and long-lasting protection of single-shot COVID-19 vaccine in the U.S. Johnson & Johnson. September 21, 2021.

Links:

COVID-19 Research (NIH)


New Initiative Puts At-Home Testing to Work in the Fight Against COVID-19

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COVID-19 Update: Community At-Home Testing
Credit: nito/Shutterstock

Thankfully COVID-19 testing is now more widely available than it was earlier in the pandemic. But getting tested often still involves going to a doctor’s office or community testing site and waiting as long as a couple of days for the results. Testing would be so much easier if people could do it themselves at home. If the result came up positive, a person could immediately self-isolate, helping to stop the coronavirus that causes COVID-19, SARS-CoV-2, from spreading any further in their communities.

That’s why I’m happy to report that the Centers for Disease Control and Prevention (CDC), in close collaboration with state and local public health departments and with NIH, has begun an innovative community health initiative called “Say Yes! COVID Test.” The initiative, the first large-scale evaluation of community-wide, self-administered COVID-19 testing, was launched last week in Pitt County, NC, and will start soon in Chattanooga/Hamilton County, TN.

The initiative will provide as many as 160,000 residents in these two locales with free access to rapid COVID-19 home tests, supplied through NIH’s Rapid Acceleration of Diagnostics (RADx) initiative. Participants can administer these easy-to-use tests themselves up to three times a week for one month. The goal is to assess the benefits of self-administered COVID-19 testing and help guide other communities in implementing similar future programs to slow the spread of COVID-19.

The counties in North Carolina and Tennessee were selected based on several criteria. These included local infection rates; public availability of accurate COVID-19 tracking data, such as that gathered by wastewater surveillance; the presence of local infrastructure needed to support the project; and existing community relationships through RADx’s Underserved Populations (RADx-UP) program. Taken together, these criteria also help to ensure that vulnerable and underserved populations will benefit from the initiative.

The test is called the QuickVue At-Home COVID-19 Test. Developed with RADx support by San Diego-based diagnostic company Quidel, this test is easily performed with a nasal swab and offers results in just 10 minutes. Last week, the test was among several authorized by the Food and Drug Administration (FDA) for over-the-counter use to screen for COVID-19 at home.

Participants can order their QuickVue test kits online for home delivery or local pick up. A free online tool, which was developed with NIH support by CareEvolution, LLC, Ann Arbor, MI, will also be available to provide testing instructions, help in understanding test results, and text message reminders about testing. This innovative tool is also available as a smartphone app.

A recent study, supported by the RADx initiative, found that rapid antigen testing for COVID-19, when conducted at least three times per week, achieves a viral detection level on par with the gold standard of PCR-based COVID-19 testing processed in a lab [1]. That’s especially significant considering the other advantages of a low-cost, self-administered rapid test, including confidential results at home in minutes.

The Say Yes! COVID Test initiative is an important next step in informing the best testing strategies in communities all over the country to end this and future pandemics. The initiative will also help to determine how readily people accept such testing when it’s made available to them. If the foundational data looks promising, the hope is that rapid at-home tests will help to encourage people to protect themselves and others by following the three W’s (Wear a mask. Wash your hands. Watch your distance), getting vaccinated, and saying “Yes” to the COVID-19 test.

Reference:

[1] Longitudinal assessment of diagnostic test performance over the course of acute SARS-CoV-2 infection. Smith RL, Gibson LL, Martinez PP, Heetderks WJ, McManus DD, Brooke CB, et al. medRxiv, 2021 March 20.

Links:

CDC and NIH bring COVID-19 self-testing to residents in two locales, NIH News Release, March 31, 2021

Say Yes! COVID Test

Rapid Acceleration of Diagnostics (RADx) (NIH)

COVID-19 Testing (CDC)

Quidel Corporation (San Diego, CA)

Coronavirus (COVID-19) Update: FDA Continues to Advance Over-the Counter and Other Screening Test Development, FDA News Release, March 31, 2021

NIH Support: National Heart, Lung, and Blood Institute; National Institute of Biomedical Imaging and Bioengineering


Is One Vaccine Dose Enough After COVID-19 Infection?

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COVID-19 vaccination record card
Credit: iStock/Bill Oxford

For the millions of Americans now eligible to receive the Pfizer or Moderna COVID-19 vaccines, it’s recommended that everyone get two shots. The first dose of these mRNA vaccines trains the immune system to recognize and attack the spike protein on the surface of SARS-CoV-2, the virus that causes COVID-19. The second dose, administered a few weeks later, boosts antibody levels to afford even better protection. People who’ve recovered from COVID-19 also should definitely get vaccinated to maximize protection against possible re-infection. But, because they already have some natural immunity, would just one shot do the trick? Or do they still need two?

A small, NIH-supported study, published as a pre-print on medRxiv, offers some early data on this important question [1]. The findings show that immune response to the first vaccine dose in a person who’s already had COVID-19 is equal to, or in some cases better, than the response to the second dose in a person who hasn’t had COVID-19. While much more research is needed—and I am definitely not suggesting a change in the current recommendations right now—the results raise the possibility that one dose might be enough for someone who’s been infected with SARS-CoV-2 and already generated antibodies against the virus.

These findings come from a research team led by Florian Krammer and Viviana Simon, Icahn School of Medicine at Mount Sinai, New York. The researchers reasoned that for folks whose bodies have already produced antibodies following a COVID-19 infection, the first shot might act similarly to the second one in someone who hadn’t had the virus before. In fact, there was some anecdotal evidence suggesting that previously infected people were experiencing stronger evidence of an active immune response (sore arm, fever, chills, fatigue) than never-infected individuals after getting their first shots.

What did the antibodies show? To find out, the researchers enlisted the help of 109 people who’d received their first dose of mRNA vaccines made by either Pfizer or Moderna. They found that those who’d never been infected by SARS-CoV-2 developed antibodies at low levels within 9 to 12 days of receiving their first dose of vaccine.

But in 41 people who tested positive for SARS-CoV-2 antibodies prior to getting the first shot, the immune response looked strikingly different. They generated high levels of antibodies within just a few days of getting the vaccine. Compared across different time intervals, previously infected people had immune responses 10 to 20 times that observed in uninfected people. Following their second vaccine dose, it was roughly the same story. Antibody levels in those with a prior infection were about 10 times greater than the others.

Both vaccines were generally well tolerated. But, because their immune systems were already in high gear, people who were previously infected tended to have more symptoms following their first shot, such as pain and swelling at the injection site. They also were more likely to report other less common symptoms, including fatigue, fever, chills, headache, muscle aches, and joint pain.

Though sometimes it may not seem like it, COVID-19 and the mRNA vaccines are still relatively new. Researchers haven’t yet been able to study how long these vaccines confer immunity to the disease, which has now claimed the lives of more than 500,000 Americans. But these findings do suggest that a single dose of the Pfizer or Moderna vaccines can produce a rapid and strong immune response in people who’ve already recovered from COVID-19.

If other studies support these results, the U.S. Food and Drug Administration (FDA) might decide to consider whether one dose is enough for people who’ve had a prior COVID-19 infection. Such a policy is already under consideration in France and, if implemented, would help to extend vaccine supply and get more people vaccinated sooner. But any serious consideration of this option will require more data. It will also be up to the expert advisors at FDA and Centers for Disease Control and Prevention (CDC) to decide.

For now, the most important thing all of us can all do to get this terrible pandemic under control is to follow the 3 W’s—wear our masks, wash our hands, watch our distance from others—and roll up our sleeves for the vaccine as soon as it’s available to us.

Reference:

[1] Robust spike antibody responses and increased reactogenicity in seropositive individuals after a single dose of SARS-CoV-2 mRNA vaccine. Krammer F et al. medRxiv. 2021 Feb 1.

Links:

COVID-19 Research (NIH)

Krammer Lab (Icahn School of Medicine at Mount Sinai, New York, NY)

Simon Lab (Icahn School of Medicine at Mount Sinai)

NIH Support: National Institute of Allergy and Infectious Diseases


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