Therapies For COVID-19 Prevention

Other than vaccines, there are currently no therapies approved or authorized for emergency use for prevention of COVID-19.

At the beginning of the pandemic, there was a lot of buzz around hydroxychloroquine as a preventive agent for both pre-exposure prophylaxis among healthcare workers and post-exposure prophylaxis for healthy household contacts; however, clinical trials to date have failed to show its clinical benefit.1–5 Ivermectin is another agent that was of interest for COVID-19 prevention early in the pandemic. One form of this drug is approved to treat parasitic worms in humans, and other forms are used to treat or prevent parasites in animals. It is not an antiviral agent. In fact, the Food and Drug Administration has issued a warning against the use of this drug for the prevention of COVID-19 after several reports of people needing medical support after self-medicating with it. Studies of ivermectin for SARS-CoV-2 are ongoing, and it should only be used exactly as prescribed in the setting of a clinical trial.6

Supplements such as zinc, vitamin C, and vitamin D are another area of interest in COVID-19 prevention. Although they are believed to reduce the duration and severity of viral infections by boosting the body’s immune response, they too have failed to demonstrate efficacy for prevention and treatment in randomized controlled trials.7,8

Monoclonal antibodies approved under emergency-use authorization for the treatment of COVID-19 are also being investigated as prophylaxis. Preliminary data of a phase 3 trial of casirivimab-with-imdevimab COVID-19 monoclonal- antibody therapy suggest that a low-dose of this combination can reduce the risk of symptomatic infection in people after exposure to someone diagnosed with SARS-CoV-2 in their home.9 This antibody cocktail is currently approved for non-hospitalized people with mild- to-moderate COVID-19 at high risk of progressing to more severe symptoms of the disease.10

Several ongoing clinical trials continue to investigate these and other pharmacological agents, supplements, and nutraceuticals, including antiretroviral drugs, omega 3 polyunsaturated fatty acids, and probiotics.11–13


  1. Abella BS, Jolkovsky EL, Biney BT, et al. Efficacy and safety of hydroxychloroquine vs placebo for pre-exposure SARS-CoV-2 prophylaxis among health care workers: a randomized clinical trial. JAMA Intern Med. 2021;181:195-202.
  2. Barnabas RV, Brown ER, Bershteyn A, et al. Hydroxychloroquine as postexposure prophylaxis to prevent severe acute respiratory syndrome coronavirus 2 infections: a randomized trial. Ann Intern Med. 2021;174:344-352.
  3. Boulware DR, Pullen MF, Bangdiwala AS, et al. A randomized trial of hydroxychloroquine as postexposure prophylaxis for COVID-19. N Engl J Med. 2020;383:517-525.
  4. Mitjà O, Corbacho-Monné M, Ubals M, et al. A cluster-randomized trial of hydroxychloroquine for prevention of COVID-19. N Engl J Med. 2021;384:417-427.
  5. Rajasingham R, Bangdiwala AS, Nicol MR, et al. Hydroxychloroquine as pre-exposure prophylaxis for COVID-19 in healthcare workers: a randomized trial. Clin Infect Dis. 2020; Oct 17: Epub ahead of print.
  6. Food and Drug Administration (FDA). Why you should not use ivermectin to treat or prevent COVID-19. ( Accessed 4/20/2021.
  7. Jayawardena R, Sooriyaarachchi P, Chourdakis M, Jeewandara C, Ranasinghe P. Enhancing immunity in viral infections, with special emphasis on COVID-19: a review. Diabetes Metab Syndr. 2020;14:367-382.
  8. Thomas S, Patel D, Bittel B, et al. Effect of high-dose zinc and ascorbic acid supplementation vs usual care on symptom length and reduction among ambulatory patients with SARS-CoV-2 infection: the COVID A to Z randomized clinical trial. JAMA Netw Open. 2021;4:e210369.
  9. Regeneron press release. Phase 3 prevention trial showed 81% reduced risk of symptomatic SARS-CoV-2 infections with subcutaneous administration of REGEN-COV™ (casirivimab with imdevimab). ( Accessed 4/20/2021.
  10. FDA. Fact sheet for health care providers Emergency Use Authorization (EUA) of casirivimab and imdevimab. ( Accessed 4/20/2021.
  11. Alavian G, Kolahdouzan K, Mortezazadeh M, Torabi ZS. Antiretrovirals for prophylaxis against COVID-19: a comprehensive literature review. J Clin Pharmacol. 2021;61(5):581-590.
  12. Hathaway D, Pandav K, Patel M, et al. Omega 3 fatty acids and COVID-19: a comprehensive review. Infect Chemother. 2020;52:478-495.
  13. Olaimat AN, Aolymat I, Al-Holy M, et al. The potential application of probiotics and prebiotics for the prevention and treatment of COVID-19. npj Sci Food. 2020;4:17.



Updates in the Treatment and Prevention of COVID-19​

FDA Authorizes Lower Dose of Intravenous and Subcutaneous Dose of Casirivimab and Imdevimab Antibody Cocktail

The Food and Drug Administration authorized lower-dose (1200 mg) casirivimab and imdevimab monoclonal-antibody infusion therapy for nonhospitalized people with COVID-19 who have risk factors for disease progression. The Emergency Use Authorization (EUA) is supported by data from a phase 3 trial showing a consistent 70% reduced risk of hospitalization or death with either the lower dose or the higher dose (2400 mg) originally authorized. Subcutaneous administration of casirivimab and imdevimab was granted EUA based on scientific evidence to date regarding its safety and efficacy. Infusion-related reactions of grade 2 or higher have been observed in 0.2% of people who have received IV therapy; 12% of those treated subcutaneously have experienced injection-site reactions.

This antibody combination has shown efficacy in vitro against variants of concern identified in the United States with origins from Brazil (P.1/Gamma) and South Africa (B.1.351/Beta).

In May 2021, the definition of eligible patients for outpatient COVID-19 monoclonal antibody therapies was expanded to include more medical conditions and other factors, such as race or ethnicity, that increase the risk for severe disease.

Subcutaneous Administration of Casirivimab and Imdevimab Reduced the Risk of Symptomatic COVID-19 by 81% Among Household Contacts

Top-line results from a phase 3 trial showed that the combination of casirivimab and imdevimab reduced the risk of symptomatic infections by 81% among household contacts of SARS-CoV-2 infected individuals. The trial enrolled 1,505 individuals who did not have COVID-19 symptoms or anti-SARS-CoV-2 antibodies, but who lived in the same household as an individual who tested positive for SARS-CoV-2 within the prior 4 days. A single subcutaneous injection of casirivimab and imdevimab provided rapid protection to those with exposure to SARS-CoV-2 at home, with protection against symptomatic infections ranging from 72% in the first week to 93% in subsequent weeks. Individuals who developed symptomatic infections despite casirivimab and imdevimab therapy had a shorter duration of symptoms compared with those who received placebo (1 week vs 3 weeks, respectively). Infected individuals who received therapy also cleared the virus faster. Adverse events (AEs) occurred in 20% of patients receiving casirivimab and imdevimab and 29% of patients receiving placebo. Injection site reactions, all of which were grades 1-2, occurred in 4% of patients in the treatment group and 2% of placebo participants.

Casirivimab and Imdevimab Significantly Reduced Progression to Symptomatic COVID-19 in Recently Infected Asymptomatic Patients

In a phase 3 trial of 204 recently infected asymptomatic COVID-19 patients, subcutaneous administration of casirivimab and imdevimab reduced the overall risk of progressing to symptomatic COVID-19 by 31%, and by 76% after the third day. In addition to reducing the risk of symptomatic infections, the top-line results report that the combination of casirivimab and imdevimab shortened the total number of weeks patients experienced symptoms by 45% and reduced the viral burden by more than 90%. No patients withdrew from the trial due to AEs in either group. Casirivimab and imdevimab are investigational drugs with emergency use authorization for the treatment of individuals with mild-to-moderate COVID-19 who are at high-risk of progressing to severe COVID-19 or hospitalization. Casirivimab and imdevimab (REGEN-COV™) continues to be evaluated in clinical trials in multiple settings for COVID-19, including the open-label RECOVERY trial of hospitalized patients in the UK.

Johnson & Johnson COVID-19 Vaccine Administration Paused

The Centers for Disease Control and Prevention (CDC) and the Federal Drug Administration (FDA) are recommending a pause in the use of the Ad26.COV2.S vaccine developed by Johnson & Johnson (Janssen) as they review data involving 6 reported cases of a rare and severe type of blood clot in individuals after vaccination. The vaccine has been administered to more than 6.8 million individuals in the US. In all 6 reported cases, a type of blood clot called cerebral venous sinus thrombosis (CVST) occurred in combination with low platelet levels (thrombocytopenia). Treatment of CVST differs from other blood clots and administration of heparin may be dangerous in these patients. All 6 cases occurred among women aged 18 to 48 years and symptoms usually occurred 6 to 13 days after vaccination. People who develop severe headache, abdominal pain, leg pain, or shortness of breath within 3 weeks after vaccination should contact their healthcare provider.


Regeneron Press Release. FDA Authorizes Lower 1,200 mg Intravenous and Subcutaneous Dose of REGEN-COV™ (Casirivimab and Imdevimab). Antibody Cocktail to Treat Patients with COVID-19. Available at:–301305941

Regeneron Press Release. Phase 3 Prevention Trial Showed 81% Reduced Risk of Symptomatic SARS-CoV-2 Infections with Subcutaneous Administration of REGEN-COV™ (Casirivimab and Imdevimab). April 12, 2021. Available at:

Regeneron Press Release. Phase 3 Treatment Trial in Recently Infected Asymptomatic Patients Showed REGEN-COV™ (Casirivimab and Imdevimab) Significantly Reduced Progression to Symptomatic COVID-19. April 12, 2021. Available at:

FDA Statement. Joint CDC and FDA Statement on Johnson & Johnson COVID-19 Vaccine. April 13, 2021. Available at: