Key takeaways:
Xocova (ensitrelvir) and Paxlovid (nirmatrelvir/ritonavir) are in the same drug class, but they are approved for different indications. Paxlovid treats COVID-19. Xocova prevents it after an exposure.
Xocova prevents 67% of cases of symptomatic COVID-19 when started within 72 hours of a household exposure.
Xocova and Paxlovid are both strong CYP3A inhibitors — which means they have lots of problematic drug interactions. Xocova also has a longer half-life than Paxlovid, so you have to worry about those interactions for 10 days after the last dose.
You may have heard that there’s a new tool in the COVID toolbelt. It’s a new antiviral called Xocova (ensitrelvir), and it was approved by the FDA in May 2026. But it’s different from Paxlovid (nirmatrelvir/ritonavir).
Xocova is also an oral protease inhibitor, but with a very different job. In the U.S., it doesn’t treat COVID-19 — it prevents it after exposure.
Here’s how the two antivirals compare.
Xocova for PEP
The FDA approved Xocova for post-exposure prophylaxis (PEP) in adults and adolescents 12 and older who’ve been exposed to someone with COVID. It’s a protease inhibitor that blocks viral replication between exposure and COVID symptom onset.
XOCOVA is not approved to treat active infection in the U.S. In Japan, where it’s been available since 2022, it carries both indications.
Here’s what else you need to know:
Dosing: Three 125 mg tablets on day 1 (375 mg total), then one tablet daily on days 2 through 5.
Timing: Xocova can only be given within a 72-hour window of when the household contact first began displaying symptoms. Like Paxlovid, this is a drug that only works if it’s started fast.
Drug interactions: Xocova is a strong CYP3A inhibitor, so it affects levels of CYP3A-dependent drugs and supplements the same way Paxlovid does. And because it clears far more slowly, those effects can linger for up to about 10 days after the last dose. There are several medications with the potential for serious interactions. So a full interaction check before prescribing is critical, and those medications need to be modified or held for a longer time.
Renal dosing: Xocova needs no dose adjustment for renal impairment (Paxlovid requires a lower dose below an eGFR of 60, and another adjustment below 30). For a patient with chronic kidney disease, that’s one less thing to calculate.
Pregnancy: Xocova carries a fetal toxicity warning based on animal data, so verify pregnancy status before you prescribe it. Contraception is warranted during the 5-day course and for 2 weeks after the final dose.
Clinical trial results
Xocova’s approval rests on the SCORPIO-PEP trial — a double-blind, randomized clinical trial published in the New England Journal of Medicine that randomized 2,387 household contacts of someone who had tested positive for COVID. They started a 5-day course of Xocova or placebo within 72 hours of the contact’s first symptoms. Xocova cut the rate of symptomatic COVID illness by 67% through day 10 (about 3% of contacts on the medication got sick, versus 9% on placebo). Among people who were at higher risk, the benefit was larger.
One important thing to note: The trial only counted symptomatic infection — not hospitalization or death, since these were too rare to measure (there were no hospitalizations or deaths in either group in the study). So the benefit is fewer symptomatic cases after a known exposure, not fewer hospitalizations or decreased severity of disease.
Why Paxlovid isn’t PEP
If the two drugs hit the same target, why isn’t Paxlovid for PEP as well? Pfizer actually studied that. In its own post-exposure trial, Paxlovid lowered the rate of symptomatic infection — but not by enough to reach statistical significance. So it was never approved for PEP. Molnupiravir — which was granted Emergency Use Authorization status by the FDA in December 2021 — also failed at the same job.
For Xocova, the inverse is true. In its treatment trial, SCORPIO-HR, the drug clearly lowered viral levels — but it didn’t make people feel better any faster than placebo, missing the endpoint that mattered. In other words, it was good at clearing virus, but not at actually shortening illness. That’s why the FDA only approved it for prevention, not treatment.
On the other hand, Paxlovid cut hospitalization or death by 89% in unvaccinated adults at high risk for severe illness in a phase 2-3 trial. So in the U.S., the two split the work: Paxlovid for treatment, Xocova for prevention.
Comparing Xocova and Paxlovid at a glance
Here’s a quick comparison chart of Xocova vs Paxlovid.
| Xocova | Paxlovid |
|---|---|---|
FDA indication | • Post-exposure prophylaxis | • Treatment of mild-to-moderate COVID in high-risk patients |
Timing | Within 72 hours of index case’s symptom onset | Within 5 days of the patient’s own symptom onset |
Mechanism | 3CL (main) protease inhibitor | 3CL protease inhibitor + ritonavir booster |
Dosing | 375 mg day 1, then 125 mg once daily (days 2–5) | 300 mg/100 mg twice daily × 5 days |
Pivotal trial results | SCORPIO-PEP: 67% relative reduction in symptomatic COVID at day 10 | EPIC-HR: 89% relative reduction in hospitalization or death at day 28 |
Drug interaction tail | ~10 days (half-life ~48 hr) | ~3 days ( half-life ~6 hr) |
Renal dosing | No adjustment needed | Reduce at eGFR <60; further adjustment at <30 |
Notable adverse effects | • Headache, diarrhea, cough | • Dysgeusia, diarrhea |
Where Xocova fits your clinical practice
Every clinician who has prescribed Paxlovid knows the drill: confirm high-risk status, start within 5 days, then spend more time screening the medication list for CYP3A interactions than writing the script. With Xocova, the interaction screening is just as important, but its use is different.
Xocova makes the most sense for high-risk patients with a recent, known exposure. An immunocompromised household contact or an elderly spouse of someone who just tested positive, for example, are patients for whom you’d want to lower the odds of getting sick at all. It’s the first oral option for these types of patients.
But Xocova doesn’t replace anything. Vaccination still does the durable, systemic work, and Paxlovid is still your best bet for actual treatment. Xocova just fills the short window right after an exposure.
The bottom line
Xocova is the first oral antiviral proven to prevent symptomatic COVID-19 after an exposure – a gap that Paxlovid tried and failed to fill. Think of Xocova and Paxlovid as same-class tools for opposite moments: Xocova after someone’s been exposed, and Paxlovid when someone’s symptomatic. And don’t forget, you need to start the medication quickly, and you still need to go through the entire medication interaction checklist.
Why trust our experts?
References
Alpizar, S. A., et al. (2023). Molnupiravir for intra-household prevention of COVID-19: The MOVe-AHEAD randomized, placebo-controlled trial. Journal of Infection.
Hammond, J. et al. (2022). Oral nirmatrelvir for high-risk, nonhospitalized adults with COVID-19. The New England Journal of Medicine.
Hammond, J. et al. (2024). Oral Nirmatrelvir–ritonavir as postexposure prophylaxis for COVID-19. The New England Journal of Medicine.
Havens, J. P., et al. (2025). Implementation of an online drug–drug interaction screener for the STRIVE ensitrelvir trial for COVID-19. Open Forum Infectious Diseases.
Hayden, F. G, et al. (2026). Ensitrelvir for COVID-19 postexposure prophylaxis in household contacts. The New England Journal of Medicine.
Luetkemeyer, A. F., et al. (2025). Ensitrelvir for the treatment of nonhospitalized adults with COVID-19: Results from the SCORPIO-HR, phase 3, randomized, double-blind, placebo-controlled trial. Clinical Infectious Diseases.
Pfizer. (n.d.). Paxlovid dosing and administration.
Shinogi. (2026). Shionogi announces FDA approval of xocova (ensitrelvir), the first and only oral option to help prevent COVID-19 following exposure.
Shinogi. (2026). XOCOVA (ensitrelvir) tablets, for oral use [package insert].
