Frequently Asked Questions About COVID-19 Clinical Studies

A: There are over 7 billion people in the world. COVID-19 is affecting everyone, and vaccines are needed to end the pandemic. Now that we have vaccines that have proven to be very effective at preventing severe COVID-19 disease, why do we need to continue COVID-19 vaccine research?

There are three main reasons:

  1. If we find several vaccines that work, we can end the pandemic sooner.
  2. In addition to meeting the demand, we also need vaccines that can work for many kinds of people around the world.
  3. We still need more data over a longer period of time to answer key questions.

Read more about continuing research after some vaccines have been approved by the FDA.

A: There is no licensed vaccine or antibody against severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2), which is the virus that causes coronavirus disease 2019 (COVID-19). Scientists are working very hard to develop a vaccine and an antibody and do the research to determine whether they are safe and effective against SARS-CoV-2.

A: There are 4 phases of clinical studies.

Phase 1 Clinical Studies - Phase 1 studies test the safety of a product like a COVID-19 vaccine or a monoclonal antibody. This means seeing if there are side effects, and whether the human body can tolerate the vaccine or antibody. The experimental vaccine or monoclonal antibody is often compared to a group that receives a placebo, a substance such as sterile saltwater that has no active ingredients. These studies are conducted with a small group of people (usually less than 100) and typically last 12 to 18 months.

Phase 2 Clinical Studies - Phase 2 studies look at questions such as the maximum tolerated dose, the optimal schedule for giving the vaccine or monoclonal antibody (how many doses, and at what time intervals), and whether the immune system is having the desired responses. These responses can include the production of antibodies, the production of T cells, and other immune system markers. These studies are conducted with a medium-size population of volunteers (usually a few hundred to 1000) and the studies can last up to 2 years.

Phase 2b Clinical Studies - Phase 2b studies are a way to get an early look at whether the vaccine or monoclonal antibody is effective at preventing COVID-19 disease. They are sometimes known as Proof of Concept or Test of Concept studies. A group of several thousand people who are at increased risk for infection or disease are enrolled, and the studies can last about 2-5 years. Based on the data from these studies, researchers can see whether the results seem favorable, supporting moving ahead to Phase 3. If the results are less favorable, it means that researchers can redirect their efforts and save the expenses of large Phase 3 studies.

Phase 3 Clinical Studies - Phase 3 studies are where researchers can ask the questions, "Does this vaccine or monoclonal antibody prevent new infections? Or if people do become infected, does the vaccine or monoclonal antibody help them control the infection so that it doesn’t become severe disease?" These studies involve many thousands of people, usually including some participants who are at increased risk for infection.

Phase 4 Clinical Studies - Phase 4 studies may take place after the vaccine or monoclonal antibody has been found to be effective in some populations, and are utilized to gather additional information about safety and effectiveness by testing the vaccine or monoclonal antibody in additional populations such as children or pregnant women. They are sometimes known as bridging studies, or post-licensure studies. These studies may be conducted in anyone seeking a COVID-19 prevention option from their physician.

A: No. That type of study design is known as a challenge study. Instead, we are using a design known as “randomized, blinded, placebo-controlled” studies. We will enroll people who are more likely to be exposed to SARS-CoV-2 infection and COVID-19 illness. Some participants will get the vaccine, and some will get a placebo, which is a sterile saline solution that does not have any vaccine in it. We expect that some people will be exposed to the virus in their everyday lives, and may become sick. We will compare the 2 groups to see if there are fewer people who get sick in the vaccine group than in the placebo group. This is how we will know if the vaccine works.

A: Unlike guinea pigs, people can say yes or no about joining a study. All study volunteers must go through a process called informed consent that ensures they understand all of the risks and benefits of being in a study, and those volunteers are reminded that they may leave a study at any time without losing any of their rights or benefits. The COVID-19 Prevention Network (CoVPN) takes great care to make sure people understand the study fully before they decide whether or not to join. All CoVPN studies follow US federal regulations on research, as well as international ethical standards and any country-specific requirements for the countries where our research is conducted.

A: In order to find a vaccine or antibody that works in all kinds of people, it is necessary to test them in all kinds of people. This is especially true for groups of people that have been hardest hit by the COVID-19 pandemic. Protecting the well-being of study volunteers is the greatest responsibility in every study, and the CoVPN works to make sure that our studies follow the highest ethical standards. These studies are done in collaboration with local scientists and researchers and community representatives with oversight by ethics and regulatory groups in each country. Many studies are done in sub-Saharan Africa, Europe, North America, and South America at the same time and we follow the same procedures and international standards no matter where the study takes place.

A: No. The vaccines and antibodies being tested by the CoVPN are preventive products. They must be tested on volunteers who do not have COVID-19, because our goal is to keep people healthy. There are other research groups that are conducting studies of treatments that might be used for people who already have COVID-19.

A: It is true that vaccines often have side effects, but those are typically temporary (like a sore arm, low fever, muscle aches and pains) and go away after a day or two. Many studies have proven that there is no link between vaccines and autism. There is also no link between childhood vaccination and autism. The British doctor who originally published the finding about vaccines and autism has since been found to have falsified his data and was stripped of his license to practice medicine. The value of protection among vaccinated individuals and to the public has made vaccines one of the top public health measures in history, second only to having a clean water supply.

A: It is true that the search for vaccines and monoclonal antibodies against COVID-19 has been happening very quickly, but we’re not cutting any corners or skipping any steps. All the usual measures to ensure the safety of study participants or the general public are being followed. Our primary concern is the safety of study participants, and the general public who will ultimately get a vaccine that is proven to be effective.

Here are some of the differences that enable us to speed up the search for vaccines and monoclonal antibodies against COVID-19. When scientists develop a vaccine or an antibody, they usually don’t start phase 2 studies until the phase 1 studies have finished. And they don’t start phase 3 studies until after the phase 2 studies have ended. In the search for a COVID-19 vaccine or antibody, we are overlapping some steps instead of doing them one after the other. We are also planning studies that are much larger, such as 30,000 participants instead of 4,000-5,000. Having more people means that study objectives can be met in a shorter period of time. Additionally, enrolling more participants from varied backgrounds enables us to ensure that the products we are testing will be safe for everyone.

Another big difference is the financial investment that has been made by the U.S. government. This investment has made it possible for companies to manufacture larger amounts of their vaccines in advance without having to take all of the financial risks themselves. If a study shows that a vaccine is not effective, the vaccine doses that have been made can be destroyed, without causing the company to fail financially.

A third factor is the commitment from regulatory groups like the U.S. Food and Drug Administration. They have strict standards and regulations that must be followed to approve a vaccine or an antibody. The FDA has even made its standards tougher for COVID vaccines by setting minimum requirements for the effectiveness of products in order to have them approved. By doing this, the FDA has confirmed their strong commitment to only approving a vaccine that could offer immunity to the majority of the population.

These changes to the process, investments, and regulatory standards mean that we will be able to find a preventive vaccine or antibody sooner, without compromising the safety of people who join the studies or the general public.

A: No, there is no way to guarantee whether you will get the vaccine or the placebo. All the studies will be blinded, which means that neither you nor the clinic staff will know who is getting which product. When someone decides to enroll, it will be a computer who makes a random assignment to the study product group or the placebo group, and only the pharmacist will know which product you get. These steps are necessary to ensure that no assumptions are made, and any immune responses or side effects are dealt with equitably, without favoritism.

A: The trials are enrolling people with a whole variety of health conditions, because we know that having underlying health conditions is one of the factors that puts people at risk for more severe COVID-19 illness. We can't comment on the specifics of any particular study, because each one is different. If you complete the survey to join our Volunteer Screening Registry, a local study team would be able to follow up if they feel you are a good match to a study they have available. Once they reach out to you, you can have a more specific conversation to address your particular concerns and health conditions.

A: We have clinics all over the U.S., but we’re not able to provide a list of specific locations at this time, in part because site selection is still being finalized for each study. Different clinics will be running each of the different studies that are coming up in the next several months. Some trials will also be done internationally. Additional sites are often added to a study to follow where COVID-19 outbreaks are happening or to better serve priority populations, and some sites may close early if they have enrolled their allotted number of participants. The list of clinics that are participating can change frequently.

If you complete the survey on our website, your information will go into our Volunteer Screening Registry. This will enable a local clinic near you to follow-up with you if they feel you would be a good match for a study they have available. This contact could happen soon, or it may be in several months, as there are several studies taking place over the next 6 months. If you do not get contacted, it could mean that there is no participating clinic near you, or that you are not a good match to the eligibility criteria of the study the clinic has available.

A: Yes, people who join a study get compensated for their time and inconvenience. The amount per visit varies depending on how long the visit is and the procedures that take place. The amount also varies from city to city, because the cost of living is different between large metropolitan areas compared to smaller towns and rural areas. The details about compensation will be explained when a person goes through the informed consent process at a local clinic to join a study.

A: Operation Warp Speed, a program of the U.S. government, is working to purchase enough COVID-19 vaccines to provide universal coverage for the United States. This is done in 2 ways: by buying vaccine doses now, and through an “option to purchase program.” All 5 major companies whose products are being tested in U.S. government-funded studies are participating. This will allow the country to have enough doses for the 220 million adults and 110 million children for whom vaccines could potentially be administered.

We expect that these 5 different vaccines may have different safety profiles and/or differences in the immune responses people have to them. This could be especially true for women of childbearing age, children, and the elderly. If only a few vaccines are effective, the CDC and the U.S. government’s ACTIV program will establish recommendations for priority populations that should receive the vaccines first. This would be temporary until the option to purchase program results in having enough vaccine doses for optimal coverage. We are confident that this approach will provide enough vaccine doses to vaccinate those in vulnerable populations to protect as many people as possible.

As part of the U.S. government effort, it is our obligation to ensure that everyone in America is provided with a safe and effective vaccine as soon as possible. Since the vaccine will be purchased by the U.S. government, the vaccine will be affordable for the public. We recognize that vulnerable populations in many underserved communities are among those at highest risk for suffering the consequences of COVID-19. We are committed to vigorous minority community outreach and maximizing access in these communities, including the Black/African American, Latinx, and American Indian/Alaska Native/Native Hawaiian populations.

A: When you have completed the submission of your survey, you will see a message with the heading “Success!” which means that we have successfully received your information. Our system does not send out an email confirmation message.

Your information will be provided to a study site closest to your location. If the study site thinks you may qualify for a particular study, they will reach out to you as soon as possible about participating. This could be soon, or it may be in several months, as there are several studies taking place over the next 6 months. We will never ask for your financial, credit, or bank account information. We will never ask for an ID number over the phone.

A: There are many clinical trials evaluating therapies and vaccine candidates against severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2), the virus that causes coronavirus disease 2019 (COVID-19), as well as studies of people who have recovered from infection. To find out more about those clinical trials, please visit NIAID’s Volunteer for COVID-19 Clinical Trials page or


A novel coronavirus is a new coronavirus that has not been previously identified in people. Coronavirus disease 2019 (COVID-19) is caused by the new virus called severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2). This is not the same as the coronaviruses that commonly circulate among humans and cause mild illness, like the common cold.

A: No. People of all ages can be infected by SARS-CoV-2, the virus that causes COVID-19. However, older people and people with some pre-existing health conditions are more at risk of severe illness. 1

A: COVID-19 can affect anyone, regardless of their race or ethnicity. However, data show that it is disproportionately impacting Black/African American, Latinx, and American Indian/Alaska Native/Native Hawaiian populations. This is largely due to social and structural factors that impact some communities more than others. These factors include poverty, poor housing conditions, challenges with accessing medical care, and limited resources, among others.

A: No. Antibiotics help stop bacterial infections and are not effective against viruses such as SARS-CoV-2.1

A: No. Some people who do get SARS-CoV-2, the virus that causes COVID-19, experience flu-like symptoms. COVID-19 currently has a higher death rate than the flu and appears to be more contagious than the flu.2 We do not know yet whether COVID-19 will change with the seasons like influenza. In the US, the CDC recommends that everyone aged 6 months and over receive an influenza vaccine every year.

A: Yes. Scientists have found that people who have SARS-CoV-2 and have no symptoms (i.e., asymptomatic) can still pass along SARS-CoV-2 to others.2 In fact, people infected with SARS-CoV-2 seem to be most infectious before they even show signs and symptoms.

A: The U.S. Food and Drug Administration (FDA) is reviewing many drugs as potential treatments, but nothing has yet been approved to treat or prevent COVID-19. The FDA is also identifying treatments, such as Remdesivir, to help ease the symptoms and help people recover more quickly.3

A: Face masks can reduce your chances of getting SARS-CoV-2, but the primary purpose of face masks is to protect others from you in case you are infected, especially if you are not showing symptoms. It is recommended that the public wear cloth masks, including homemade masks, to help prevent transmitting the virus to other people.4

A: To date there is no information or evidence to suggest that SARS-CoV-2 can be transmitted by mosquitos. This disease is a respiratory virus spread primarily through droplets when an infected person coughs, sneezes or has discharge from the nose.1

A: Vaccines against other diseases do not offer protection against SARS-CoV-2. This is a new virus that will need its own vaccine, and researchers are working on developing a safe and effective one.4

A: SARS-CoV-2 can be transmitted in all areas, including hot/humid and cold climates.1

A: While gargling with warm saltwater can make a sore throat feel better, it has no effect on SARS-CoV-2.5

A: There are simple things you can do to help keep yourself and others healthy. Wash your hands often with soap and water for at least 20 seconds, especially after blowing your nose, coughing, sneezing, going to the bathroom, and before eating or preparing food.

When in public, wear a cloth face mask that covers your mouth and nose. Avoid touching your eyes, nose, and mouth with unwashed hands. Stay home when you are sick. Cover your cough or sneeze with a tissue, then throw the tissue in the trash.2 Stay 6 feet apart from other people when you are out in public.

A: No. You can help stop COVID-19 by knowing the signs and symptoms, which can include:

  • Fever
  • Cough
  • Shortness of breath
  • Chills
  • Sore throat
  • New loss of taste and/or smell

Seek medical attention immediately if you or someone you have been exposed to has emergency warning signs, including:

  • Trouble breathing
  • Persistent pain or pressure in the chest
  • New confusion or not able to be woken up (from sleep)
  • Bluish lips or face

This list of symptoms is NOT all inclusive and is being updated as new information becomes available. Please consult your medical provider for any other symptoms that are severe or concerning.2

General FAQs

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A: We’re here to help. If you still have questions after reading the above FAQs, please contact us at, or call (206) 667-2001. Due to the large volume of inquiries, our response may be significantly delayed. We will prioritize responding to questions that are not addressed in these FAQs. Please note:

  • The COVID-19 Prevention Network does not provide personal medical advice or diagnoses.
  • If you live in the U.S. and are experiencing a medical emergency, call 911 and notify the operator if you think you might have COVID-19.
  • If you think you have been exposed to COVID-19 and develop a fever and symptoms such as a cough or difficulty breathing, call your healthcare provider immediately for medical advice.


  1. World Health Organization, Coronavirus advice for the public: Myth busters
  2. Centers for Disease Control and Prevention (CDC), Coronavirus COVID-19
  3. Centers for Disease Control and Prevention (CDC), Key Facts
  4. U.S. Food and Drug Administration, Coronavirus (COVID-19) Update: FDA Continues to Facilitate Development of Treatments
  5. Johns Hopkins Bloomberg School of Public Health, COVID-19 Myths vs. Realities
  6. Johns Hopkins Medicine, Coronavirus Disease 2019: Myth vs. Fact

Interested in volunteering for a COVID-19 Prevention Clinical Study?

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