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

Canadian Center for Vaccinology — Whooping Cough (Halifax, NS, Canada)

The Canadian Center for Vaccinology is conducting a challenge study for whooping cough at IWK Health Centre that could help develop new, better vaccines. The main goal of the first study is to determine the amount of B. pertussis (dose) that results in only mild symptoms (similar to a common cold) among 70-90% of those who received that dose. All participants will receive appropriate antibiotic treatment to prevent severe illness. The study is looking for healthy volunteers aged 18-40 who would be able to stay in the challenge unit for the full 16-21 days and nights. Challenge study participants receive $350 per day/night spent inside the challenge unit and $50 per follow-up visit. Contact the trial team at or 902-266-6510 or visit their website for further details.

University of Maryland Center for Vaccine Development — Influenza Positive Donors (Baltimore, MD, USA)

If you have been diagnosed with laboratory-confirmed influenza infection and have had an onset of influenza-like symptoms (fever ≥100.2°F and cough or sore throat) in the past 48 hours, you may qualify to participate in CVD’s flu-transmission study as a flu donor. This flu transmission study is designed to examine the person-to-person transmission of community-acquired influenza in healthy adults aged 18 to 59. This study involves up to a 5-day stay in a hotel research quarantine unit, one outpatient clinic visit, and one telephone visit. Compensation is up to $1,900. To reach the trial team, call 410-706-8800 (8am-4pm).

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

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.

University of Maryland Center for Vaccine Development — Shigella (Baltimore, MD, USA)

The purpose of this study is to test the effectiveness of an investigational oral phage product gainst shigella. They are recruiting healthy participants aged 18-50. Study duration will be approximately 8 months. Volunteers will complete 5 outpatient visits and have a 9 to 11-day inpatient stay. Compensation is up to $4,100. For more information and to express interest, call 410-706-8800 or visit the study website 

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

This is a registry for future influenza transmission studies in a quarantine research facility with a risk of influenza infection. Healthy adults aged 18 to 49 may remain on the registry for up to 5 years and will be contacted to participate in future flu transmission studies in a quarantine research facility. See more details here.

Johns Hopkins — ETEC Challenge Study (Baltimore, MD, USA)

The purpose of this study is to learn about how many people will get diarrhea after a dose of wild type enterotoxigenic E. coli  (ETEC). They are recruiting healthy participants aged 18-50. The study is six months long and includes 1-2 screening visits, 1 10-day inpatient stay, 1 follow up visit, and 1 follow up phone call. Compensation is up to $3860. For more information and to express interest, visit 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.

Oxford Vaccine Group – Paratyphoid (Oxford, Birmingham, Liverpool, and Southampton, UK)

The purpose of this study is to investigate whether a novel vaccine can prevent paratyphoid fever. The study is recruiting healthy participants aged 18 to 55, The total study participation time is 14 months, during this time you will be required to attend your local trial site for regular study visits and the coordinating centre in Oxford for 3 specific study visits; transport to Oxford from your local study site will be provided. Compensation will cover time, inconvenience, and travel. To learn more or express interest, visit the website where you can find contact information for each study site.

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.

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 – 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.