An oral treatment study for women with recently diagnosed, symptomatic COVID-19.

The purpose of this clinical trial is to learn about how study medicine (Paxlovid, which contains nirmatrelvir and ritonavir) is changed and eliminated from the body, as well as its safety, and the extent to which side effects can be tolerated for treatment of pregnant women with mild or moderate COVID-19 compared to non-pregnant women with mild or moderate COVID-19. PAXLOVID was recently authorized by the US FDA for emergency use in high-risk patients over the age of 12, including pregnant women; however, it has not yet been studied in pregnancy as part of a clinical trial.

If you are a woman who has recently been diagnosed with COVID-19, participation in this study may be an option to consider not only for yourself, but to potentially help millions of other women around the world.    

Who may participate

Joining a clinical trial is an important and personal decision. Your doctor may have mentioned this study to you, or perhaps you found your way here by yourself. Either way, thank you for your interest.

This study may be an option for women who  

  • tested positive for COVID-19 within the last 5 days
  • currently have at least 1 symptom related to COVID-19

Pregnant women are eligible to participate in this study, but you must be in the 2nd or 3rd trimester (14 weeks to 34 weeks and 6 days) of your pregnancy.

There are other requirements for taking part in this study. The study doctor will explain these to you.




18-50 years



Each clinical study has its own guidelines for who can participate, called eligibility criteria.  However, only the research study staff can determine if you qualify to enroll in the study.

What to expect

If you are interested in participating, the study team will schedule a visit to determine if this study is a good fit for you.

If you are eligible and decide to participate, you will take PAXLOVID twice a day for 5 or 6 days, for a total of 10 doses. There is no placebo in this study and all participants will receive PAXLOVID. 

If you are pregnant, you will be enrolled in the study until you deliver or for 36 days (whichever is longer).  You will attend at least 8 scheduled appointments.  If you are not pregnant, you will be enrolled for about 36 days and will need to attend at least 7 scheduled appointments. Appointments may be in-person or remote.

Also, you will need to track your doses in an electronic diary (eDiary). The study team will show you how to use this.

You may be reimbursed for study-related expenses.

Length of study treatment

5-6 days

Number of study visits

Up to 9 visits


PAXLOVIDTM is a combination of the medicines nirmatrelvir and ritonavir. PAXLOVID was studied in a previous clinical trial of non-hospitalized adults with symptomatic COVID-19 who had at least 1 risk factor for progressing to severe COVID-19. The results from that study showed that participants who received PAXLOVID were less likely to be hospitalized or die from COVID-19 compared to participants who received a placebo.

On December 22nd, 2021, the US FDA granted an Emergency Use Authorization of PAXLOVID for the treatment of mild to moderate COVID-19 in adults and children 12 years of age and older weighing at least 40 kg who are at high risk of developing severe COVID-19, including pregnant women. PAXLOVID is considered investigational in this study because it has not been studied in pregnant or breastfeeding women previously.


Portrait of woman for COVID-19 – Pfizer Clinical Trials
Portrait of woman for COVID-19 – Pfizer Clinical Trials

Frequently asked questions

Do I need to be pregnant to participate in this study?

No, this study is enrolling both pregnant and non-pregnant women so that doctors can determine if pregnancy impacts how PAXLOVID is absorbed and processed in the body. If you are interested in participating, please call 1-800-887-7002 and reference study number NCT05386472.

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Am I guaranteed to receive the study medicine?

Yes, all participants enrolled in this study will receive the study medicine PAXLOVID. This study does not include a placebo (medicine with no active ingredient).

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What is a placebo?

A placebo does not contain any active ingredients, but the study medicine and placebo look alike.

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What are the possible side effects?

All medicines have the potential to cause side effects. The study doctor will discuss the possible risks and benefits of participating in this study with you before you choose to enroll. You can choose to leave the study at any time.

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What if this study is not right for me?

You can choose to leave the study at any time, for any reason, including after you have discussed it with the study doctor. Choosing to leave the study will not affect your prenatal or future medical care. 

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Does it cost anything to participate?

The study medicine and all study-related medical procedures are provided at no cost. You don’t need health insurance to join a clinical study.  However, you (or your health insurance provider) may be responsible for medical expenses that are part of your usual healthcare. Talk with your study team or review the informed consent document to find out exactly what is covered.

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