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Can a second janssen shot cut severe COVID-19 in south africa?

NCT ID NCT05148845

Vaccine Sponsor: Wits Health Consortium (Pty) Ltd Source: ClinicalTrials.gov ↗

What the study statuses mean

This study's is highlighted.

Recruitment status, easiest to join first

Recruiting now
This trial is taking on new participants right now.
Not yet recruiting
Registered, but not yet taking participants.
By invitation only
Not open to general applications. Only people the study team invites can take part.
Paused
Paused for now. It may or may not start again.
Ongoing
Running, but no longer taking on new participants.
Completed This study
The trial has finished. Results may not be published yet.
Stopped early
Stopped early, before it reached the end. That can be for many reasons, including safety.
Cancelled
Cancelled before anyone took part.

Expanded access (not trials)

Expanded access
Not a trial. This treatment can be requested outside a study, case by case, for people who qualify.
Expanded access (paused)
Not a trial. The treatment can normally be requested outside a study, but is unavailable right now.
Expanded access (ended)
Not a trial. The treatment could once be requested outside a study, but no longer can.
Approved
The treatment has been approved, so it is available normally rather than through this programme.

When the status isn't known

Details not published
The full record has not been published yet, so there is little to show here.
Status unknown
This status has not been confirmed recently, so it may be out of date.

First seen Sep 01, 2026 · Last updated Sep 02, 2026 · Updated 1 time

Summary

This study tests whether a booster dose of the Janssen COVID-19 vaccine lowers the risk of severe COVID-19, hospitalizations, and deaths in adults who received a single Janssen shot at least six months earlier. Researchers will compare boosted participants with those who were not boosted, as well as with vaccinated and unvaccinated groups in South Africa. The trial enrolls around 500,000 adults from the earlier Sisonke study, including pregnant and breastfeeding women.

What this could mean

Our plain-language read of the trial. This is informational only, not medical advice or a prediction.

Active substance
A booster dose of the Janssen (Ad26.COV2.S) COVID-19 vaccine given to people who already received a single Janssen shot at least six months earlier.
What this could lead to
If the booster works, it could offer a practical way to strengthen protection against severe COVID-19 for millions of people who received a single-dose vaccine.
What could go wrong
This is an open-label study without a placebo group, so results may be influenced by who chooses to get boosted. The vaccine may also provide less protection against new variants.

This is an AI summary of the original study and may miss details. Read our disclaimer.

Study facts

What this study's own registry entry says, in plain language.

Phase

Phase 3

Large-scale testing in a bigger group. Usually the last step before a treatment can be approved.

Participants

500,000 people

The number who actually took part.

Started

Nov 2021

Finished

Jun 2023

Lead sponsor

Other sponsor

The registry's catch-all category, for sponsors it does not file as a company, a government agency, or a research network.

Who can take part

This study's own entry requirements. Only the study team can say for certain whether you qualify.

Ages

18 years and older

Sex

Anyone

Healthy volunteers

Accepted

You do not need to have the condition being studied to take part.

Show the full entry requirements

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria * Age 18 and older * All Sisonke participants * Received a priming Ad26.SARS.COV.2.S vaccination as part of the Sisonke study at least 6 months prior * Participants who are pregnant or report breastfeeding at the time of enrolment may be included. * Willingness and ability to comply with vaccination plan and other study procedures. * Capable of giving electronic or personal signed informed consent as described in Appendix 5, which includes compliance with the requirements in this protocol. Exclusion Criteria: * Participants who have received boosting vaccination through other means. * Any significant acute or chronic medical condition, situation or circumstance that in the opinion of the PI/designee makes the participant unsuitable for participation in the study, or jeopardises the safety or rights of the participant * Current participation in any other research studies that would interfere with the objectives of this study. The determination of whether participation in another study would be exclusionary for a given participant will be made by the PI/designee. * Participants with a history of heparin-induced thrombocytopenia or TTS

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Conditions

The condition(s) this trial relates to.

COVID-19 prevention target

As listed by the trial registrant

The condition terms exactly as the trial's registrant entered them.

SARS CoV 2 infection

Contacts and locations

Locations

  • Botha's Hill Clinical Research Site

    Bothas Hill, KwaZulu-Natal, 3660, South Africa

  • CAPRISA Vulindlela Clinical Research Site, Dr Disebo Makhaza

    Durban, KwaZulu-Natal, South Africa

  • CAPRISA eThekwini Clinical Research Site, Dr

    Durban, KwaZulu-Natal, 4001, South Africa

  • Chatsworth Clinical Research Site

    Durban, KwaZulu-Natal, 4030, South Africa

  • Clinical HIV Research Unit (CHRU),

    Johannesburg, Gauteng, 2000, South Africa

  • Desmond Tutu Health Foundation - Masiphumelele Research Office

    Cape Town, 7975, South Africa

  • Desmond Tutu Health Foundation CTU J52 Old Main Building Groote SchuurHospital

    Cape Town, Western Cape, 7925, South Africa

  • Emavundleni Research Centre

    Cape Town, Western Cape, 7781, South Africa

  • FAMCRU (Family Clinical Research Unit),

    Cape Town, Western Cape, 7505, South Africa

  • Josha Research

    Bloemfontein, Free State, 9300, South Africa

  • MeCRU Clinical Research Unit

    Pretoria, Gauteng, 0000, South Africa

  • Mzansi Ethical Research Centre

    Middleburg, Mpumalanga, 1050, South Africa

  • Ndlovu Research Centre

    Pretoria, Gauteng, South Africa

  • Nelson Mandela Academic Clinical Research Unit (NeMACRU)

    Mthatha, Eastern Cape, 5100, South Africa

  • PHOENIX Pharma Pty Ltd

    Port Elizabeth, Eastern Cape, 6001, South Africa

  • Perinatal HIV Research Unit (PHRU), SOWETO

    Johannesburg, Gauteng, 1862, South Africa

  • Perinatal HIV Research Unit Kliptown

    Johannesburg, Gauteng - South, 1809, South Africa

  • Qhakaza Mbokodo Research Clinic

    Ladysmith, KwaZulu-Natal, 3370, South Africa

  • Setshaba Research Centre,

    Pretoria, Gauteng, 0152, South Africa

  • South African Vaccine Initiative (SATVI)

    Worcester, Western Cape, 6850, South Africa

  • TASK Applied Science, Brooklyn Chest Hospital Premises

    Cape Town, Western Cape, 7530, South Africa

  • TASK Applied Science, Delft Day Hospital Premises

    Cape Town, Western Cape, 7100, South Africa

  • TASK Applied Science, Dr Ivans Toms Clinic Premises

    Cape Town, Western Cape, 7100, South Africa

  • TASK Central

    Cape Town, Western Cape, 7530, South Africa

  • TASK Clinical Research Centre

    Cape Town, Western Cape, 7530, South Africa

  • TASK Eden

    George, Western Cape, 6529, South Africa

  • The Aurum Institute Clinical Research Centre, Pretoria

    Pretoria, Gauteng, 2059, South Africa

  • The Aurum Institute Klerksdorp Clinical Research Centre

    Klerksdorp, North West, 2571, South Africa

  • The Aurum Institute: Rustenburg Clinical Research Centre, Dr Lawrence

    Rustenburg, 0299, South Africa

  • The Aurum Institute: Tembisa Clinical Research Centre

    Johannesburg, Gauteng - South, 1632, South Africa

  • Tongaat Clinical Research Site, Dr

    Tongaat, KwaZulu-Natal, 4400, South Africa

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