Here you can browse by country to view all challenge studies that, to our knowledge, are currently running public recruitment efforts.

Sign up below to join our volunteer base and you’ll be updated on studies happening in your area. If you do sign up for a study (even if you don’t eventually make it through screening!), please let us know — you can email us at


United Kingdom

United States

None (for now). Those in the Toronto area can visit this page to learn more about a proposed study for hepatitis C.

Jenner Insitute - COVID-19 (Oxford)

Researchers at the Oxford Jenner Institute would like to develop a safe human infection model (challenge model) where volunteers who have been vaccinated against Covid-19 are exposed to the Omicron BA.5 subvariant of SARS-CoV-2 virus in a controlled manner. Information gained from this initial study will enable future research that may help scientists understand what kind of immune response stops people from being infected with Covid-19 and the impact of the virus on the immune system. The study involves 4 visits and a 17 day stay in a quarantine unit over a period of around 6 months. Participants will be reimbursed approximately £4,935 for their time and travel. More information can be found on the study website.

Oxford Vaccine Group - Malaria (Oxford)

The purpose of this study is to investigate how the immune system responds to repeated malaria infection, and involves 1 vaccination and 3 malaria challenges. The study is recruiting healthy adults aged 18-45. There will be 88 to 95 visits over 20 months. Compensation  is between £9,325 to £9,955. To learn more visit the study website where you can where you can access the Participant Information Sheet, screening questions and register your interest.

hVivo - Respiratory viruses (London and Manchester, UK)

hVivo, a contract research organization, is continuously screening participants for the challenge studies that they run. Learn more at the FluCamp website.

Liverpool – Pneumococcus (Liverpool, UK)

The Liverpool School of Tropical Medicine is conducting challenge research on a bacteria called Pneumococcus, which is the main cause of pneumonia. They are looking for participants in the Liverpool area who are 18-50 years old, generally well, and non-smokers. The team says, “ In the study, you may receive a pneumococcal vaccine, you will have a small amount of bacteria put in your nose and samples taken to learn about the immune response to the bacteria. This will help us develop better vaccines to prevent pneumonia (as well as sepsis and meningitis).” To learn more, please visit the study website or contact the Respiratory Infection Team by calling 07740 410 290 or emailing You can also register for their general volunteer database here.

Imperial College London & Oxford University – COVID-19 (London and Oxford, UK)

Imperial College London is running a human challenge study for the Delta variant of SARS-CoV-2 so that researchers can learn more about the infection and test new vaccines and treatments in the future. They are looking for individuals aged 18-30 who have been vaccinated against COVID-19 and in good health. Participants will be given a dose of coronavirus and then monitored for a minimum of 10-14 days at the quarantine unit in London, with five follow up visits over the following year. Compensation is up to £4,470. You would need to pay for your own transportation to and from the trial site. If you are interested in this study opportunity, please visit their website and complete the pre-screening questionnaire online to find out if you might be eligible to take part.

Oxford University is also collaborating as a study site for the trial; you can sign up here.

Imperial College London - Respiratory Infection Registry (London, UK)

Imperial College London is looking for healthy, individuals aged 18-64 years to provide a blood sample every 3 months for up to 6 years, and potentially be recruited into future virus challenge and vaccine studies exploring respiratory illnesses. As part of the study, blood tests will be taken to measure your levels of immunity against different strains of influenza virus. Whether you are invited to participate in a future challenge or vaccine study will depend on your suitability, partly as a result of these tests. Compensation is £30 per visit. To learn more about this registry or register your interest, please visit its webpage.

University of Maryland Center for Vaccine Development —  Respiratory Registry (Baltimore, MD)

This is a registry study seeking to recruit healthy adults (18-64 years old) willing to be contacted in the future for participation in influenza virus challenge, vaccine and other respiratory studies. The study team will collect vaccination history, medical history, multiple blood, and other samples to understand immunity for new research studies. There will be 4 study visits per year for up to 6 years and compensation of $100 per visit.

Johns Hopkins — Dengue Vax/Zika Challenge (CIR 369) (Baltimore, MD)

The Zika human challenge study model was very recently established with pioneering work at Johns Hopkins. The purpose of this study is to test the effects of the Zika virus against a Dengue vaccine. For more information and to express interest, visit the study website.