Real-World Evidence: Observational Retrospective Study in Dominican Republic Points to Ivermectin as PrEP

Real-World Evidence Observational Retrospective Study in Dominican Republic Points to Ivermectin as PrEP

Last September, TrialSite interviewed the president of the Rescue Group, the largest healthcare group in the Caribbean nation of the Dominican Republic. At that time, TrialSite’s founder Daniel O’Connor spoke with Jose Natalio Redondo, president of the health group, who reported that half a year into the pandemic, his team had already treated at least 6,000 patients with ivermectin with excellent results. He reported that the infection rates anecdotally were far lower with his group as compared to patients at other health centers. But this couldn’t serve as evidence. Although, Dr. Natalio expressed the intention at the time to leverage their electronic health record for a large formal study that was ongoing. The Rescue Group went ahead and sponsored an observational, retrospective cohort study based on real-world data at two medical centers within the group—Centro Medico Bournigal (CMBO) in Puerto Plata and Centro Medico Punta Cana (CMPC) in Punta Cana, Dominican Republic. Registered in, the sponsor sought to determine whether a weekly oral regimen of ivermectin serves as an effective pre-exposure prophylactic method (PrEP) to inhibit the transmission of SARS-CoV-2 in healthcare workers. The Dominican sponsor recently shared the results and although not yet peer reviewed nor published, the fact that the nation’s largest health system generated significant real world data is well worth review. The results show promise: after 28 days of follow-up, the ivermectin-based PrEP offered significant protection from COVID-19 infection.

The Study

This observational retrospective multicenter cohort database study was executed in two medical centers belonging to the Rescue Group, including Centro Medico Bournigal (CMBO) in Puerto Plata and Centro Medico Punta Cana (CMPC) in Punta Cana, Dominican Republic. 

The health system’s Grupo Rescue task force initiated the study back in June 29, 2020 and completed the effort on July 26, 2020, involving 713 active healthcare personnel involved in the statistical analysis. Out of the total 713 study participants, 326 participated in a weekly prophylactic program using ivermectin as a therapeutic agent targeting COVID-19. 387 healthcare professionals were assigned to the control group and didn’t receive ivermectin.

This study team used an ivermectin 6mg oral tablet on a weekly basis at a dosage of 0.2 mg/kg equivalent for four weeks. The team employed the SPSS Propensity Score Matching procedure in a 1:1 ratio to evenly calculate the cohorts making up the 271 subjects each.

The Results

By day 28, during the follow up period, the team discovered a significant protection afforded by ivermectin as a PrEP of infection from COVID-19. For example, those that took ivermectin were observed at 1.8% as compared to 6.6% for those who didn’t take ivermectin for a p-value equaling 0.006 as well as a reported reduction of the risk of positive Chain Reaction of Real-Time Polymerase Transcription (RT-PCR) COVID-19 test by 74% (RT-PCR) COVID-19 test by 74% (HR 0.26, 95% CI [0.10,0.71).

The study demonstrates a clear benefit of the use of ivermectin on a weekly basis for what the sponsor deems “compassionate preventative methods” for healthcare professionals.

The Sponsor

The Rescue Group is a leading national private health network in the Caribbean nation of Dominican Republic. The Rescue Group operates three hospitals as well as affiliated referral hospitals, urgent care facilities and an in-home service in addition to 17 emergency hotel medical centers. Hospitals within Rescue Group earn quality accreditations such as Punta Cana Medical Center, which became the first hospital in the Dominican Republic to receive international GOLD Accreditation by Qmentum International-Accreditation Canada

Lead Research/Investigator

Jose Morgenstern, Department of Infectious Diseases, advisor, Centro Medico Punta Cana, Punta Cana, Dominican Republic, Corresponding Author

Call to Action: Follow the link to read the study results located at the preprint server medxRiv.


  1. Please tell us if the study was randomized. (In another description I heard of this study, the answer was “no” – if it was indeed this very study.)
    If not, what effort was made to document the prevalence of risk factors in the two groups? Were the two groups balanced as to risk factors?
    Were the ivermectin group more attentive to mask wearing and other hygiene measures that would have lowered their risk?
    How about zinc and vitamin D3 intake in the two groups before and during the study?
    The difference in infection rate is impressive, but as you can see, without randomization and a placebo control, the study is suggestive, but doesn’t really move us any further along.
    Minor editorial point:
    You can’t take “a 6 mg tablet” to achieve a dosage of 0.2 mg/kg unless you weigh 30 kg. If you are a very small adult and weigh 60 kg, two tablets would do it. If you are closer to 90 kg (198 lbs) three tablets would be the dosage.
    Important dosage information missing:
    Were the tablets taken with food to increase absorption, or on an empty stomach as one would do if treating an intestinal parasite?
    Thanks for the report!

    1. “This study team used an ivermectin 6mg oral tablet on a weekly basis at a dosage of 0.2 mg/kg”, iow two 6mg tablets for a 12mg dose, appropriate for small adults weighing about 130 lbs.

      The tablet size does not determine the dosage. Just as you take multiple 3mg tablets for the desired dosage, so you would take multiple 6mg tablets.