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SARS CoV 2 InfectionPhase 3Sisonke BoostNCT05148845

Sisonke 2 - A COVID-19 Vaccine Boost Open Label Study.

A Phase 3 study testing Sisonke Heterologous mRNA-1273 boost after prime with Ad26.COV2.S in people with SARS CoV 2 Infection, run by Wits Health Consortium (Pty) Ltd at 31 sites in South Africa.

Completed

Finished. The study has ended and is not enrolling. Results may be posted on the official record.

Official record
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Trial summary

To evaluate the effectiveness of the single dose Ad26.COV2.S COVID-19 vaccine plus a homologous boostwith Ad26.COV2.S COVID-19 vaccine among Sisonke participants as compared to unboosted Sisonkeparticipants; vaccinated; and unvaccinated populations in South Africa Read more about this study

Who is it for?
Ages 18 years and olderHealthy volunteers can take part
Conditions the study is for
SARS CoV 2 Infection
What is being tested?
Sisonke Heterologous mRNA-1273 boost after prime with Ad26.COV2.S
Type of treatment
Vaccines
Could I receive a placebo?
No, everyone receives an active treatment
How many people
500,000 participants
Where
31 sitesSouth Africa
Study dates
10 Nov 2021to 30 Jun 2023
Phase
Phase 3
Are there results?
None posted in the registry

Key requirements

Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.

  • Ages 18 years and older
  • All sexes
  • Healthy volunteers accepted
  • Adult, Older adult

Who may be able to join

  • 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.

Who cannot join

  • 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

Trial locations and contacts

31 sites in 1 country.

31 sites in 1 country

South Africa31 sites

  • Josha Research

    Bloemfontein, Free State, 9300

  • Botha's Hill Clinical Research Site

    Bothas Hill, KwaZulu-Natal, 3660

  • TASK Applied Science, Delft Day Hospital Premises

    Cape Town, Western Cape, 7100

  • TASK Applied Science, Dr Ivans Toms Clinic Premises

    Cape Town, Western Cape, 7100

  • FAMCRU (Family Clinical Research Unit),

    Cape Town, Western Cape, 7505

  • TASK Applied Science, Brooklyn Chest Hospital Premises

    Cape Town, Western Cape, 7530

  • TASK Central

    Cape Town, Western Cape, 7530

  • TASK Clinical Research Centre

    Cape Town, Western Cape, 7530

  • Emavundleni Research Centre

    Cape Town, Western Cape, 7781

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

    Cape Town, Western Cape, 7925

  • Desmond Tutu Health Foundation - Masiphumelele Research Office

    Cape Town, 7975

  • CAPRISA eThekwini Clinical Research Site, Dr

    Durban, KwaZulu-Natal, 4001

  • Chatsworth Clinical Research Site

    Durban, KwaZulu-Natal, 4030

  • CAPRISA Vulindlela Clinical Research Site, Dr Disebo Makhaza

    Durban, KwaZulu-Natal

  • TASK Eden

    George, Western Cape, 6529

  • Perinatal HIV Research Unit (PHRU), SOWETO

    Johannesburg, Gauteng, 1862

  • Clinical HIV Research Unit (CHRU),

    Johannesburg, Gauteng, 2000

  • The Aurum Institute: Tembisa Clinical Research Centre

    Johannesburg, Gauteng - South, 1632

  • Perinatal HIV Research Unit Kliptown

    Johannesburg, Gauteng - South, 1809

  • The Aurum Institute Klerksdorp Clinical Research Centre

    Klerksdorp, North West, 2571

  • Qhakaza Mbokodo Research Clinic

    Ladysmith, KwaZulu-Natal, 3370

  • Mzansi Ethical Research Centre

    Middleburg, Mpumalanga, 1050

  • Nelson Mandela Academic Clinical Research Unit (NeMACRU)

    Mthatha, Eastern Cape, 5100

  • PHOENIX Pharma Pty Ltd

    Port Elizabeth, Eastern Cape, 6001

  • MeCRU Clinical Research Unit

    Pretoria, Gauteng, 0000

  • Setshaba Research Centre,

    Pretoria, Gauteng, 0152

  • The Aurum Institute Clinical Research Centre, Pretoria

    Pretoria, Gauteng, 2059

  • Ndlovu Research Centre

    Pretoria, Gauteng

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

    Rustenburg, 0299

  • Tongaat Clinical Research Site, Dr

    Tongaat, KwaZulu-Natal, 4400

  • South African Vaccine Initiative (SATVI)

    Worcester, Western Cape, 6850

Other trials in South Africa

About this study

Official title: Open-label, Single-arm Phase 3B Implementation Study to Evaluate the Effectiveness of the Homologous Boost of Ad26.COV2.S COVID-19 Vaccine Following the Prime Dose Among Sisonke Participants in South Africa(VAC31518COV30XX)

To evaluate the effectiveness of the single dose Ad26.COV2.S COVID-19 vaccine plus a homologous boostwith Ad26.COV2.S COVID-19 vaccine among Sisonke participants as compared to unboosted Sisonkeparticipants; vaccinated; and unvaccinated populations in South Africa

Read the detailed description

Purpose To evaluate the effectiveness and safety of the single dose Ad26.COV2.S (Jansen) COVID-19 vaccine plus a homologous boost with Ad26.COV2.S (Janssen) COVID-19 vaccine among Sisonke participants as compared to unboosted Sisonke participants

In addition the investigators will continue to evaluate VE of the Sisonke Boost compared to:

  1. Vaccinated populations pre boosts ii) Unvaccinated populations in South Africa.

Study design Open-label, single-arm phase 3B vaccine implementation study

Rationale South Africa is severely affected by the global COVID-19 epidemic, and following the initial prime vaccination among HCWs in the first 4 months of 2021. New data has demonstrated the safety and effectiveness of a booster dose given two months or more after the initial Ad26.COV2.S. This provides the rationale and feasibility for the evaluation of a homologous booster vaccine dose to the cohort of vaccinated Sisonke participants to inform the larger vaccine rollout.

Study participants Sisonke participants age 18 and over working in the South African public and private health care sector (approx N=500 000) who were enrolled in Sisonke and have not subsequently had a further booster vaccine dose.

Study sites Department of Health Vaccine Administration Sites across South Africa supported by the Sisonke (Together) (VAC31518COV3012) Trial Research Site Investigators and Study Staff

Study duration Participants will receive a homologous Ad26.COV2.S (Janssen) booster dose of vaccine at least 6 months post the prime vaccination. The investigators will monitor outcomes utilising the DATCOV surveillance system and NHLS/NICD SARS COV-2 testing databases for up to 2 years post initial vaccination.

Study products Ad26.COV2.S by Janssen administered as a single dose followed by a single booster injection.

Primary objectives • To assess the effectiveness of Ad26.COV2.S vaccine as a homologous boost on severe COVID, hospitalizations and deaths in Sisonke participants as compared with the unboosted Sisonke populations.

Secondary objectives To assess the effectiveness of Ad26.COV2.S vaccine as a homologous boost on severe COVID, hospitalizations and deaths in Sisonke participants as compared vaccinated and unvaccinated populations of essential workers in South Africa.

  • To estimate the incidence of symptomatic SARS CoV-2 infections in Sisonke participants following a boost compared with the unboosted Sisonke populations and general vaccinated and unvaccinated population in South Africa
  • To estimate booster dose uptake among Sisonke participants in South Africa
  • To monitor the genetic diversity of breakthrough SARS CoV-2 infections.
  • To monitor safety in the case of homologous boosts in Sisonke participants.
Being tested
Sisonke Heterologous mRNA-1273 boost after prime with Ad26.COV2.S
Medical subject headings
COVID-19

What participants receive

What participants receive. In a randomised study each person is assigned to one group by chance.

  • Sisonke Heterologous mRNA-1273 boost after prime with Ad26.COV2.SBiological

    Also called Booster vaccine

    To evaluate the effectiveness and safety of the single dose Ad26.COV2.S (Jansen) COVID-19 vaccine plus a homologous boost with Ad26.COV2.S (Janssen) COVID-19 vaccine among Sisonke participants as compared to unboosted Sisonke participants

    In addition we will continue to evaluate VE of the Sisonke Boost compared to:

    1. Vaccinated populations pre boosts ii) Unvaccinated populations in South Africa.

  • Sisonke Heterologous mRNA-1273 boost after prime with Ad26.COV2.SDrug

    Sisonke Heterologous mRNA-1273 boost after prime with Ad26.COV2.S

Study groups in NCT05148845
Study groupRoleWhat they receive
Sisonke Heterologous mRNA-1273 boost after prime with Ad26.COV2.SOtherNot described
Receives: Biological: Sisonke Heterologous mRNA-1273 boost after prime with Ad26.COV2.S; Drug: Sisonke Heterologous mRNA-1273 boost after prime with Ad26.COV2.S

What is being measured

The primary outcome is the main question the study is designed to answer.

  1. To assess the effectiveness of Ad26.COV2.S (Janssen) boost vaccine on severe COVID, hospitalizations and deaths in Sisonke participants as compared to unboosted Sisonke participants (single Ad26 vaccine only)

    Rates of hospitalizations and deaths among boosted Sisonke participants versus unboosted Sisonke participants and unvaccinated populations in South Africa

    Measured: 24 Months

Secondary outcomes (5)

  1. To assess the effectiveness of Ad26.COV2.S (Janssen) boost vaccine on severe COVID, hospitalizations and deaths in Sisonke participants as compared to the vaccinated and unvaccinated populations (no vaccination) in South Africa.

    Rates of hospitalizations and deaths among boosted Sisonke participants versus unboosted vaccinated and unvaccinated populations in South Africa

    Measured: 24 Months

  2. To estimate the incidence of symptomatic SARS CoV-2 infections among boosted Sisonke ppts.

    Incidence rate of SARS CoV-2 infection as indicated by self-report and validation in national laboratory records.

    Rates of severe disease in Sisonke participants who are found to be RT-PCR positive at any time up to 2 years post prime vaccination

    Measured: 24 months

  3. To monitor the genetic diversity of breakthrough SARS CoV-2 infections

    Genetic diversity of breakthrough infection virus as determined by whole genome sequencing. This will be recovered from national laboratories.

    Measured: 24 Months

  4. To estimate booster vaccine uptake among Sisonke participants in South Africa

    Proportion of Sisonke participants approached for study participation taking part in the boost study and receiving the booster vaccine

    Measured: 24 Months

  5. To monitor safety in homologous boosts

    All SAEs and events of special interest will be collected and reported.

    Measured: 24 Months

Timeline

From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.

  1. First posted8 Dec 2021
  2. Study start10 Nov 2021
  3. Primary completion31 Jan 2022
  4. Study completion30 Jun 2023

Resources

More details

For doctors and researchers: how the study is designed, who runs it, and its registry IDs.

Study design
Study type
Interventional
Phase
Phase 3
Primary purpose
Prevention
Allocation
Non-randomised
Intervention model
Single group
Model description
Open-label, single-arm phase 3B vaccine implementation study
Masking
None (open label)
Enrolment
500,000 participants (actual)
IDs, dates and publications
ClinicalTrials.gov ID
NCT05148845
Sponsor's protocol ID
Sisonke Boost Open Label Study
Acronym
Sisonke Boost
Status last verified
Aug 2026
First submitted
9 Nov 2021
Last updated
1 Sep 2026
Results posted
No
Data monitoring committee
Yes
FDA-regulated drug
No
FDA-regulated device
No
Individual data sharing
Yes: All study team scientists will disseminate the trial results as broadly as possible. Data will be shared with JNJ prior to release to the public. The study data will be published consistent with normal scientific practices. The results from this research may also be disseminated through presentations at scientific institutions/ meetings, and/or publication in scientific journals. All publications will be uploaded to a publication repository. After sharing the results with study participants, they will be presented to communities from which participants are recruited, following Good Participatory Practice guidelines. The results will also be shared with global and local policy makers. Summary results of the trial will be made publicly available through the clinical trial registry. Any datasets used for analysis in publications can be requested by investigators via an online request to the organisation. Measures will be taken to protect identifiable information in the datasets

Publications

  • Takalani A, Robinson M, Jonas P, Bodenstein A, Sambo V, Jacobson B, Louw V, Opie J, Peter J, Rowji P, Seocharan I, Reddy T, Yende-Zuma N, Khutho K, Sanne I, Bekker LG, Gray G, Garrett N, Goga A; Sisonke Study Team. Safety of a second homologous Ad26.COV2.S vaccine among healthcare workers in the phase 3b implementation Sisonke study in South Africa. Vaccine. 2024 Feb 27;42(6):1195-1199. doi: 10.1016/j.vaccine.2024.01.066. Epub 2024 Jan 25.

    PubMed 38278629

Questions about this trial

What is this clinical trial studying?

A Phase 3 study testing Sisonke Heterologous mRNA-1273 boost after prime with Ad26.COV2.S in people with SARS CoV 2 Infection, run by Wits Health Consortium (Pty) Ltd at 31 sites in South Africa.

The full registered description is in the About this study section and the official record.

Who may be eligible to take part?

The sponsor lists 6 inclusion and 4 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.

Is this clinical trial currently recruiting?

The record says: finished, as of the sponsor's last update on 1 Sep 2026. Status can change between updates, so confirm with the study contact before making plans.

Where is the study taking place?

The record lists 31 sites in South Africa. Whether a site is taking part right now should be confirmed with that site. See every site.

What are the possible benefits and risks?

They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.

What does this phase mean?

Phase 3 studies compare the treatment with the current standard treatment or a placebo in a large group, to confirm how well it works and watch for side effects.

Not every study follows the same path, and some studies (observational studies, device studies) have no phase.

Are results available for this study?

The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.

How can a doctor refer a patient or contact the research team?

The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.

What does the primary outcome measure?

To assess the effectiveness of Ad26.COV2.S (Janssen) boost vaccine on severe COVID, hospitalizations and deaths in Sisonke participants as compared to unboosted Sisonke participants (single Ad26 vaccine only) (time frame: 24 Months). It is what the study was designed to measure, not a finding.

Where can I read the original study information?

On the ClinicalTrials.gov record for NCT05148845, which also lists 1 linked publication.

Does a listing mean the treatment is approved or proven to work?

No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.

How often is this information updated?

AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 1 Sep 2026.

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