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How fast does Paxlovid work?

Medically reviewed by Leigh Ann Anderson, PharmD. Last updated on Sep 15, 2022.

Official answer


Key Points

  • Paxlovid, an oral antiviral medication, will start to work against COVID as soon as you take it, but you may not start to feel better right away.
  • It is important you start treatment as soon as possible, within 5 days of symptom onset and testing positive for COVID. Contact your doctor or pharmacist to determine if you are eligible for treatment, even if your symptoms are mild right now.
  • If you do not feel better or if you feel worse after 5 days, be sure to call your healthcare provider for further advice.

Most people who take one 5-day course of Paxlovid (nirmatrelvir and ritonavir) recover from COVID, although there is a possibility of COVID rebound. Currently there are no reports of severe outcomes related to COVID rebound.

Paxlovid continues to be recommended for early-stage treatment (within 5 days of symptoms onset) of mild to moderate COVID-19 in people at high risk for severe disease. It can lessen symptoms and prevent hospitalization and death.

Related: How effective is Paxlovid for COVID-19?

What are symptoms of the Omicron variant?

The most common COVID symptoms from the Omicron variant are:

  • sore throat
  • fever
  • fatigue
  • body aches
  • runny nose
  • cough
  • headache.

People will experience a wide range of symptoms due to COVID. Information so far suggests that COVID-19 illness is mild-to-moderate in most people, especially with the current Omicron wave in the U.S. However, serious illness can occur and may worsen other medical conditions or lead to hospitalization or death.

Older people and people of all ages with severe, long lasting (chronic) medical conditions seem to be at higher risk of being hospitalized for COVID-19. People at higher risk include people with heart disease, lung disease, obesity or diabetes.

Related: Am I at high risk for severe COVID-19 disease?

People who have been previously infected with COVID, who are vaccinated, or both, can still get COVID, although they are at lower risk of serious disease or death due to a certain level of immunity.

Learn More: Can you take Paxlovid twice if COVID rebounds?

Do I have to isolate myself after I finish Paxlovid?

Whether you have taken Paxlovid or not, you can end home isolation after a full 5 days if:

  • your fever has resolved for 24 hours (without the use of fever-reducing medication
  • AND your symptoms are improving (eg, cough, shortness of breath).
  • You should continue to wear a well-fitting mask indoors (if around others) and in public for a full 10 days.

If you test positive again after just finishing Paxlovid you should restart the 5-day isolation period and contact your healthcare provider for further instructions.

  • You can end your COVID rebound isolation period after 5 full days if your fever has resolved for 24 hours (without the use of fever-reducing medication) and your symptoms are improving (eg, cough, shortness of breath).
  • However, you should continue to wear a well-fitting mask for another 10 days if rebound symptoms start.
  • Some people may continue to test positive even 10 days after COVID rebound begins, but are much less likely to be contagious by this time.

Most doctors do not prescribe a second round of Paxlovid for rebound. Case reports suggest that people who develop COVID rebound after completing Paxlovid have either no symptoms or mild illness. Currently there have been no reports of severe outcomes related to COVID rebound.

This is not all the information you need to know about Paxlovid (nirmatrelvir and ritonavir) for safe and effective use and does not take the place of your doctor’s directions. Review the full Paxlovid product information and discuss this information and any questions you have with your doctor or other health care provider.

  • Fact sheet for patients, parents, and caregivers. Emergency Use Authorization (EUA) of Paxlovid for Coronavirus disease 2019 (COVID-19)
  • COVID-19 Rebound After Paxlovid Treatment. CDC Health Advisory. Aug 29, 2022 at
  • Isolation and Precautions for People with COVID-19. CDC. Aug 11, 2022. Accessed Sept. 15, 2022 at
  • Omicron BA.5: What we know about this COVID-19 strain. UC Davis Health. July 12, 2022. Accessed Sept. 15, 2022 at
  • Underlying Medical Conditions Associated with Higher Risk for Severe COVID-19: Information for Healthcare Professionals. Sept. 15, 2022 at

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