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Understanding Clinical Trials


Clinical trials are conducted in phases. Each phase has a different purpose.

Phase I:  All new experimental drugs or biologic agents are first tested in laboratories to find out if they meet basic safety standards. These early studies are called “preclinical” trials because they test the new agent in a lab, not in people. After a new agent has been found to meet basic laboratory safety standards, it can then be tested in people.  The first phase of testing new agents or new indications for FDA approved agents in people is called Phase I.

The purpose of a Phase I clinical trial is to find out if a new experimental agent or treatment is safe in healthy people. These trials are small, and usually involve up to 100 healthy volunteers.  During the Phase I trial, researchers learn about the agent’s safety, possible dosages to give people, and they also learn about possible side effects. Typically, it is important to first test new agents in healthy people. Sick people can have symptoms that could be confused with side effects, or they could become sicker. Therefore, they are not usually included in Phase I trials. There are some occasions when researchers do include sick people in Phase I trials, for example, when they are testing new cancer treatment agents, however, the CIR does not test these types of agents.

Phase II An experimental agent that has met basic safety standards in a preclinical trial, and that has also been studied in at least one Phase I trial, can then be tested in a Phase II trial.

Phase II trials test the new agent in a larger group of people to evaluate the effectiveness of the drug for a particular indication. These clinical trials look at the short-term side effects and risks associated with the agent.    The trials usually involve 100-300 volunteers. Volunteers can include both healthy people and sometimes, patients. Testing the new agent in a larger group of people allows researchers to define the proper dosage and to learn more about the agent’s safety and possible side effects. Researchers also learn about how well the agent actually works to prevent illness (efficacy).

Phase III The goal of a Phase III trial is to compare the experimental agent to commonly used treatment to see if it is safe and effective.

Phase III trials are large and complex.  They often involve two or more groups of study volunteers to compare the experimental agent to the standard treatment. Studies are usually conducted in a process called blinded. In these types of studies volunteers are randomized (like flipping a coin) to determine if they will receive the experimental agent, the current standard of treatment or a placebo.  A placebo is an inactive product like salt water or like a sugar pill that allows researcher to compare reactions between groups. The research team will not know which one the volunteer received. This helps to maintain the integrity of the information gathered from the study. Volunteers are told at the end of the study which one they received.

These trials involve huge numbers of volunteers from hundreds to thousands of people. By studying the agent in so many people researchers can learn even more about how well the agent really works to prevent or treat illness.  Because these studies are so large, they are often done in several research centers at the same time. This helps to show how well the agent works in people who live in different places. For example, does a vaccine work as well for people who live in India as it does for people who live in the United States? An agent that is equally effective among many people who live in many places would be useful in helping to prevent or treat illness. Researchers continue to gather more information about the agent’s side effects and how to use the agent as safely as possible.

An agent that successfully meets safety requirements, and that works well can be submitted for licensure. In the United States a company can submit a request to the Food and Drug Administration (FDA), the regulatory agency that protects health and safety.  The FDA reviews clinical trial data and will determine if the agent is safe and effective. Once approved, the agent will be available to the public by prescription or over-the-counter.

Phase IV: After a new agent is approved and is being used there is still more that can be learned. Studies that are done after an agent is already approved are called Phase IV clinical trials. Since these types of studies are done after the agent is already for sale, they are also called “post marketing studies”.  Sometimes new side effects or benefits are found which may only become apparent after widespread use. Researchers may also study certain groups of people who may have better results with the agent than others.

Phase IV studies are designed in several different ways.  In some studies new volunteers are enrolled and studied much like a phase III trial.  In other studies, researchers may only monitor or collect information from existing data and records.  By tracking outcomes in this way, the FDA can refine its recommendations about how the new agent can be used to help or protect the greatest number of people.

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Inpatient Studies at the Center for Immunization Research (CIR)

 At the Center for Immunization (CIR), we seek to find answers to important research questions about the prevention of infectious diseases through vaccine development.  This search for answers may require CIR researchers to conduct Phase I andPhase II clinical research trials in an inpatient setting.  The CIR Inpatient Isolation Unit provides the ideal setting for this vital research.

There are two main reasons clinical research trials are done in an isolated inpatient setting at the CIR: 1) To protect the study participant:   Some study agents, usually challenge products, can make some people quite sick.  Study participants stay on the inpatient unit to receive 24 hour nursing care during these types of studies. Participants stay on the isolation unit until their laboratory test show they are no longer shedding the infectious agent.  2) To protect the public:  An infectious study agent that is given to a study participant may be harmful to the general public’s health.  Therefore, study participants stay on the inpatient unit until the possibility of giving the infection to someone else has passed. Recent studies conducted in an inpatient setting at the CIR include:

  •  ETEC (enterotoxigenic E. coli) challenge studies
  •  HMPV (human metapneumovirus) challenge study
  • Avian Influenza vaccine studies (live-attenuated nasal spray vaccines)

The CIR Inpatient Isolation Unit, completed in 2010, is located on the 4th floor of the 301 Mason Lord Drive building, on the Bayview campus of Johns Hopkins.  It is a state-of-the-art, 30-bed, Bio-safety Level (BSL) 2 facility.The design of the CIR Inpatient Isolation unit was made to ensure the safety and comfort of the study participant.  Each room has large windows for natural light. The common areas provide a relaxing atmosphere that includes large screen televisions, game tables and inviting lounge areas. Meals are provided during your stay on the isolation unit. Participants have the option of choosing menus from various caterers or preparing meals in the fully-equipped kitchen. In addition, a structured, yet relaxed schedule of activities, including optional exercise classes, arts and craft activities, and evening games is provided daily for participants. During your stay on the unit, research activities may include physical exams, vital signs (i.e. blood pressure, temperature), blood draws, urine samples, health surveys and interviews.For more information about the types of  inpatient studies, please visit our protocol synopsis page. 

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Outpatient Studies at the Center for Immunization Research (CIR) 

The Center for Immunization Research (CIR) is a world renowned clinical trial research clinic. The CIR offers Inpatient and Outpatient vaccine clinical trials. Primarily we conduct Phase I/II trials to look at the safety, efficacy and immunogenicity of vaccines for diseases such as Dengue, West Nile, Malaria, Traveler’s Diarrhea and Respiratory viruses.

What is an Outpatient Vaccine Trial?

An outpatient vaccine trial is a study that does not require an overnight stay in the hospital or research clinic. Outpatient studies are usually 6-12 months long and are conducted in the CIR Outpatient Clinic. Participants are given an investigational agent and have scheduled clinic visits to monitor how well they tolerate the investigational agent. Most studies require the clinic staff to follow up with subjects on a daily, weekly or monthly schedule.  Clinic visits can range from 2 to 4 hours, depending on the study and the type of visit.

If you’re interested in volunteering for one of our investigational vaccine studies, click here. You can also call us at 877-863-1374 or e-mail us at You will be contacted by a study team member and information about our studies and currently enrolling studies will be given to you at that time. If a study that you are interested in is full, you have the option of completing a pre-screening assessment or you may add your name to our email list to be contacted for future vaccine studies.

Pre-screening/Phone assessment:  The purpose of the pre-screening/phone assessment is to find out information about your general health. During the assessment, you will be asked questions about your health history, current medications, military service, travel history, past participation in other research studies, and demographic information.  After your pre-screening assessment is complete and you meet the screening evaluation requirements, you will be given an appointment to come to the clinic for a screening evaluation.

Screening Evaluation:  The screening evaluation process is often completed in two separate visits.  However, in some cases, additional visits may be needed. The purpose of these visits is to obtain your informed consent to participate, collect medical history and demographic information and laboratory specimens (i.e. blood, urine) that will determine your eligibility to be enrolled into one of our investigational vaccine research studies. We will also use this visit to assess your availability to participate in an investigational vaccine clinical trial. For more information about the CIR screening process click here.

It is important for you to tell the study staff about any upcoming medical procedures, vaccinations, and any medications that you will need during the study period.

 The study staff will inform you if you are NOT eligible to participate in a vaccine clinical trial.

How to Participate in an Outpatient Vaccine Trial

Informed Consent:   You will be given a copy of the Informed Consent to read. The Informed Consent contains information about the investigational agent used in the study, the process and procedures for participating in the vaccine clinical trial, the number of required study visits, and compensation.   After you have read the Informed Consent form, the study staff will review the details of the study. Please feel free to ask questions. You will be given a quiz to make sure that you understand the Informed Consent form.  Don’t panic – the quiz is “open book” meaning you will be able to use the Informed Consent form to answer the questions. After you have passed the quiz and if you agree to participate in the vaccine study, you will be given a copy of the Informed Consent form to sign and date.  You will be given a copy of the Informed Consent form to keep for your records. Please take time to read it and write down any questions that you would like to ask the study staff at your next visit.

You may withdraw your participation in the study at anytime.

Laboratory evaluations:  You must meet certain eligibility criteria to participate in a vaccine clinical trial. You will be asked to give samples such as blood and urine to help determine if you are eligible to participate in the study. Some studies may require additional samples.  Copies of your laboratory tests will be given to you upon your request. 

Clinical evaluations: A physical exam is another method used to determine if you are healthy and if you meet eligibility criteria to participate in the vaccine clinical trial.  Participants will have a physical exam that includes vital signs (ie. height, weight, blood pressure, medical history). A pregnancy test is required for all females consenting to participate in the study.  Depending on the study, other evaluations may be required.

Vaccination and Enrollment:  After we receive your laboratory test results and your screening information is reviewed by the study team, you will be contacted by a study staff member to schedule your next appointment. The eligibility criteria for the vaccination/challenge study will be reviewed, and additional blood and/or urine may be collected if needed.

Once you are found to be eligible for enrollment into the vaccine study, you will be scheduled for vaccination.  Depending on the study, the amount of time for study vaccination visit in the clinic is approximately 2-3 hours. The CIR offers light refreshments during these visits.

Before receiving your vaccination the following procedures are usually completed to ensure your continued eligibility:

  • Medical history updated and reviewed for any changes from your last visit
  • Vital signs collected and recorded
  • Physical examination repeated
  • Blood collected
  • Urine collected from all females for pregnancy testing
  • Confirmation of continued eligibility to receive the vaccine

After receiving the investigational agent you must remain in the clinic for a minimum of 30 minutes to monitor your reaction to the vaccine. During this time, you will be provided with a printed study schedule, your next appointment time, after-care instructions (if applicable), and study staff contact information.  If you receive the investigational product by injection, we will inspect your injection site before you leave the clinic.  For many of our studies, we may ask you to measure and record your temperature and any medical concerns that may arise between your clinic visits.  

It is very important for you to notify study staff of any problems that you may have after vaccination. The study staff is available to you by phone 24 hours a day. If you have  questions or concerns, we encourage you to call  at any time.

After vaccination, follow-up visits are typically scheduled. These visits are approximately 15-20 minutes and may include the following:

  • Review of recorded temperature or diary card
  • Review of any problems experienced
  • Review of any new or changed medications
  • Vital signs
  • Inspection of injection site (if applicable)
  • Physical exam or physical evaluation
  • Blood drawing
  • Repeat pregnancy test for females
  • Receive any samples that were collected by the participant

If you’re having any problems, additional samples may be collected from you for testing if requested by the investigator of the study. You may also be asked to make additional study visits. Please refer to your Informed Consent for any additional compensation for extra clinic visits.

Your safety is our most important concern! Therefore, it is very important to come to every study visit as planned so that we can collect the necessary information to monitor your health throughout the study period.   It is important for us to contact you during the study period, so please keep your contact information updated with your study coordinator. If you need to re-schedule a visit, cancel an appointment or if you are running late – please call your study coordinator as soon as possible.

Compensation for your time and travel during the study will be provided.  Ask your study coordinator at the study-specific screening when you can expect to receive your compensation.

You may withdraw from the vaccine study at any time and for any reason. If you do decide to withdraw, please contact the Principal Investigator or Study Coordinator immediately.

Your study team members are experienced, dedicated, and passionate research professionals who are committed to delivering to you a positive research experience.  We value our volunteers’ participation. For more information about vaccine research studies here at the CIR, click here.

We hope to hear from you soon!

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