Prospective Study for the FOLLOW-UP of Human Monkeypox Cases and Smallpox Vaccinees at Risk (POQS-FU PLUS)

March 17, 2026 updated by: Institute of Tropical Medicine, Belgium

Prospective On-site and Questionnaire Study for the FOLLOW-UP of Mpox Cohort at ITM PLUS Evaluation of the Longevity of B- and T-cell Immune Responses in Former Mpox Patients and Vaccine Recipients

The goal of this observational study is to describe possible physical and psychological sequelae after an mpox infection and to evaluate the longevity of B- and T-cell immune responses in former mpox patients and vaccine recipients.

The main questions it aims to answer are:

  • Are there any physical or pschological sequelae after mpox infection?
  • Is the humoral and/or cellular immune response to MPOX (or vaccinia) virus) durable?
  • Do the patients develop strong local immunity in comparison to systemic immunity?
  • How long is the virus still detectable in semen, saliva or the ano-rectal region?

Participants will answer a questionnaire, samples with blood, saliva and semen as well as anal swabs will be collected. Follow-up visits 8, 16 and 24, 36, 48, and 60 months after infection or vaccination are planned.

A healthy control group will be recruited in our HIV-PrEP clinic.

Study Overview

Status

Recruiting

Conditions

Detailed Description

Long-term problems or sequelae after an acute viral infection are described. The study aim is to investigate if long-term symptoms and sequelae can be found in the ITM human mpox infection cohort previously diagnosed and confirmed by PCR at the Institute of Tropical Medicine in Antwerp during the mpox outbreak 2022 in Belgium. The immune response after a natural mpox infection and after a smallpox vaccination will additionally analysed over time.

Consented participants Mpox patients, acute infection (n=169, 21% assumed smallpox vaccination in childhood) Mpox patients for follow-up (n=95, 20% assumed smallpox vaccination in childhood) Smallpox vaccinees, two intradermal doses (n=100) Smallpox vaccinees, two subcutaneous doses (n=100) Healthy unvaccinated controls (n=50)

Design This prospective longitudinal study has the main objectives to describe possible physical and psychological sequelae after an mpox infection and to evaluate the longevity of B- and T-cell immune responses in former mpox patients and vaccine recipients. Participants are being followed up 8, 16 and 24 months after infection or vaccination.

Sample collection Anal eSwabs from patients, controls and vaccinees Saliva (Omnigene-oral and dry swabs) from patients, controls and vaccinees Serum from patients, controls and vaccinees Optional semen samples from patients PBMC samples from a sub-group of patients, controls and vaccinees

Laboratory analysis MPXV-PCR on saliva, anorectal and optional semen samples of former mpox patients, vaccinated individuals and healthy controls Mpox-specific antibody profiling from serum Mucosal immunity (IgA, IgG) mpox-specific/reactive from anal swabs and/or saliva Enumeration of MPXV-specific effector-memory T cells via flow cytometry-based AIM or ICS assays (peptide pool stimulation or HLA-restricted multimer-based capture assays) Enumeration of MPXV-specific memory B cells or plasma cells via flow cytometry-ased AIM or ICS assays (recombinant antigen stimulation or HLA-restricted multimer-based capture assays)

Study Type

Observational

Enrollment (Estimated)

345

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

  • Name: Study Coordinator
  • Phone Number: +32(0)33455672
  • Email: bsmekens@itg.be

Study Locations

  • Belgium
      • Antwerp, Belgium, 2000
        • Recruiting
        • Institute of Tropical Medicine
        • Contact:

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Adult
  • Older Adult

Accepts Healthy Volunteers

No

Sampling Method

Non-Probability Sample

Study Population

Former mpox patients ≥18 years, diagnosed by PCR at ITM since May 2022 Smallpox vaccine recipients vaccinated at ITM since August 2022 Healthy HIV-PrEP users

Description

Mpox patients for immunological study

Inclusion criteria

  • PCR-confirmed mpox infection since May 2022
  • ≥18 years
  • Willingness to provide written informed consent
  • Willingness to follow the study schedule

Exclusion criteria

  • Any vaccination 2 weeks before or after the visits (4 weeks for life-vaccines)
  • Any immune-compromising drugs or diseases (treated and controlled HIV-infection is no exclusion criteria)
  • Any mpox reinfection since study start

Smallpox vaccinees for immunological study

Inclusion criteria

  • At least two smallpox vaccinations.
  • ≥18 years
  • Willingness to provide written informed consent
  • Willingness to follow the study schedule

Exclusion criteria

  • Any vaccination 2 weeks before or after the visits (4 weeks for life-vaccines)
  • Any immune-compromising drugs or diseases (treated and controlled HIV-infection is no exclusion criteria)
  • Any mpox infection in the past

HIV-Prep patients

Inclusion criteria

  • On HIV-PrEP and a patient from ITM
  • ≥18 years
  • Willingness to provide written informed consent
  • Willingness to follow the study schedule

Exclusion criteria

  • Born before 1976
  • Any documented or remembered smallpox vaccination or typical scar for a smallpox vaccination
  • Any vaccination 2 weeks before or after the visits (4 weeks for life-vaccines)
  • Any immune-compromising drugs or diseases
  • Any mpox infection in the past

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

Cohorts and Interventions

Group / Cohort
mpox patients
mpox cohort diagnosed and confirmed by PCR at the Institute of Tropical Medicine (ITM) in Antwerp during the recent mpox outbreak May-October 2022, 95 consented patients for follow-up
Smallpox vaccine recipients
sub-group 1: 100 participants routinely vaccinated with two subcutaneous 3rd generation smallpox vaccines sub-group 2: 100 participants routinely vaccinated with two intradermal 3rd generation smallpox vaccines
Healthy controls
50 controls recruited during HIV-PrEP consultation (no former mpox infection, no smallpox vaccination)

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Proportion of individuals with a positive mpox serology in both groups
Time Frame: 2 years
To compare the MPXV-specific serological response in naturally infected mpox male patients 8, 16 and 24 months after onset of symptoms with the MPXV-specific serological response in routinely (=2 either subcutaneous (SC) or intradermal (ID) vaccinations with an interval of 4-8 weeks) vaccinated men against smallpox 8 months after the first vaccination
2 years
Proportion of long-term problems or sequelae in mpox patients
Time Frame: 2 years
To describe any possible long-term problem or sequela after an acute human mpox infection diagnosed and confirmed by PCR at ITM since the beginning of the mpox outbreak End of May 2022
2 years

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
longevity of humoral and/or cellular immune response to mpox or vaccinia virus
Time Frame: 2 years
B-cell and T-cell characteristics in former mpox patients and smallpox vaccinees 8, 16, 24 months after symptom
2 years

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Institute of Tropical Medicine, Belgium

Investigators

  • Principal Investigator: Nicole Berens-Riha, PhD, Institute of Tropical Medicine
  • Study Director: Laurens Liesenborghs, PhD, Institute of Tropical Medicine

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

October 6, 2022

Primary Completion (Estimated)

October 1, 2027

Study Completion (Estimated)

June 1, 2028

Study Registration Dates

First Submitted

May 19, 2023

First Submitted That Met QC Criteria

May 19, 2023

First Posted (Actual)

May 30, 2023

Study Record Updates

Last Update Posted (Actual)

March 19, 2026

Last Update Submitted That Met QC Criteria

March 17, 2026

Last Verified

March 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • 1628/22

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

UNDECIDED

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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