ClinicalTrials.gg
Active, not recruitingNCT05745987SMARTUpdated Aug 12, 2026

Smallpox Vaccine for Mpox Post-Exposure Prophylaxis: A Cluster RCT

A Phase 4 interventional study of Bavarian Nordic smallpox vaccine and Typhoid VI Polysaccharide Vaccine Injectable Solution in Monkeypox, sponsored by McMaster University. Active, not recruiting at 10 sites in 3 countries. Open to participants aged 2 Years and older, including healthy volunteers. Per ClinicalTrials.gov, last updated 2026-08-12.

Sponsored by McMaster University · Phase 4, Interventional, and Prevention

Phase
Phase 4
Study type
Interventional
Enrollment
3,000
Allocation
Randomized
Ages
2 Years and older
Sex
All
01

Study summary

A cluster randomized controlled trial to determine if smallpox vaccine reduces secondary cases and symptom severity in persons exposed to mpox.

Read the detailed description

A pragmatic, adaptive, multi-site, cluster randomized trial where households with one or more persons confirmed to have mpox will be randomized to smallpox vaccine or control. The co-primary outcomes are RT-PCR confirmed mpox and symptom severity.

02

Conditions studied

  • Monkeypox

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Keywords

  • mpox
03

In context

Mpox, Monkeypox

72 studies on the registry are indexed under Mpox, Monkeypox; 30 are open to participants now.

This study's planned enrollment of 3,000 is above the median of 305 across 36 interventional studies indexed under Mpox, Monkeypox.

Browse Mpox, Monkeypox studies →

Lead sponsor

McMaster University is the lead sponsor of 741 studies on the registry; 127 are open to participants now.

Of its 7 completed or terminated interventional studies of FDA-regulated products, 3 (43%) have results posted.

Counted across the registry records on this site, refreshed daily.

04

Who can participate

Ages eligible
2 Years and older
Sexes eligible
All
Accepts healthy volunteers
Yes

Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.

Inclusion criteria

  1. Household member of person with laboratory confirmed mpox
  2. Age ≥ 2 years
  3. Within 14 days of onset of illness in mpox index case

Exclusion criteria

Exclusion Criteria:

  1. Pregnancy
  2. Breastfeeding
  3. Past serious allergic reaction to study vaccine components
  4. Previous smallpox vaccination
  5. Current or planned use of another drug at any point during study participation
Terms in these criteria, in plain language(1)

Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.

Investigational drug or device

A drug or device being studied in a clinical trial.

It may be new, or already approved and being studied for another use, dose or form. Criteria often leave out people who took part in another study of one within a recent period, commonly 30 days or five half-lives.

05

Study design

Phase
Phase 4
Primary purpose
Prevention
Allocation
Randomized
Intervention model
Parallel assignment
Masking
Triple (Participant, Investigator, Outcomes assessor)
Enrollment
3,000 participants (estimated)

Study arms

  • Experimental
    Smallpox vaccine

    Participants will receive the Bavarian Nordic smallpox vaccine 0.5 ml single-dose

    Drug: Bavarian Nordic smallpox vaccine

  • Active comparator
    Typhoid vaccine

    Participants will receive the Typhim Vi® typhoid vaccine 0.5 ml single-dose

    Drug: Typhoid VI Polysaccharide Vaccine Injectable Solution

Interventions

06

What researchers measure

Primary outcomes

  1. PCR-confirmed Mpox

    To evaluate if smallpox vaccine vs control prevents RT-PCR confirmed mpox

    Time frame: 8 weeks

  2. Symptom severity

    To evaluate if smallpox vaccine vs control affects symptom severity

    Time frame: 8 weeks

Secondary outcomes

  1. Resolution of skin lesions

    To assess the time to resolution (i.e. a new skin layer has formed) of any skin lesion

    Time frame: 8 weeks

  2. Number of skin lesions

    To assess the number of skin lesions for any participants who develop mpox

    Time frame: 8 weeks

  3. Self-reported Quality of Life

    To assess the QOL of participants using the World Health Organization Quality of Life Scale

    Time frame: 8 weeks

  4. Mpox complications

    To assess longitudinal complications for any participants who develop mpox

    Time frame: 8 weeks

  5. Mpox Pain

    To assess pain using an adapted Zoster Brief Pain Inventory

    Time frame: 8 weeks

  6. Hospitalization

    To determine all cause hospitalization over the study period

    Time frame: 8 weeks

  7. Mortality

    To determine all cause mortality over the study period

    Time frame: 8 weeks

Other outcomes

  1. Safety (SAEs, AESI)

    Solicited SAE and AESIs will be followed at 4 months and 6 months

    Time frame: 6 months

07

Study locations

10 sites
08

References and documents

Individual participant data

Plan to share: No

No publications or documents are linked to this record.

09

Updates

Tracking since Sep 25, 2026
No changes since tracking began. The registry record was last updated on Aug 12, 2026, before this site started recording changes on Sep 25, 2026. Its history is on ClinicalTrials.gov ↗
10

Registry details

Key details

Study ID
NCT05745987
Responsible party
Sponsor
First posted
Feb 27, 2023
Start date
Sep 17, 2024
Primary completion
Apr 22, 2026
Completion
Oct 20, 2026 (estimated)
Last update
Aug 12, 2026

Study contacts

Mark Loeb, MD
principal investigator · McMaster University

Oversight

Data monitoring committee
Yes
FDA-regulated drug
No
FDA-regulated device
No
View the source record on ClinicalTrials.gov ↗

Not currently enrolling

This study is active, not recruiting, as verified in Aug 2026. You cannot join it, but the record below documents what was studied.

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Discussion

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Studies of the drug tested here: MVA-BN smallpox vaccine

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