Sisonke Study

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

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Short for Sisonke Heterologous mRNA-1273 boost after prime with Ad26.COV2.S, the SHERPA Study’s primary objective is to evaluate the effectiveness of the heterologous mRNA-1273 (Moderna) boost against COVID-19 infections and severe COVID-19 disease among health care workers.

The study aims to enroll up to 15 000 Sisonke participants who have received either a single or two doses of Ad26.COV2.S. This will allow the study team to investigate the effectiveness of the Moderna COVID-19 vaccine booster against the new variants in South Africa, as well as provide the South African Health Products Regulatory Authority (SAHPRA) with additional data on this vaccine for potential licensing.


Who can enroll?

    • •  Anyone who has received either a single or two doses of Ad26.COV2.S through the Sisonke study and you are 18 years or older
    • •  If you are pregnant or breastfeeding at the time of enrolment you can join the study.
    • •  You must be willing and able to comply with the vaccination plan and other study procedures.
    • •  You must be capable and willing to provide informed consent

You may NOT enrol

  • •  If you have received any COVID-19 vaccines other than one or two doses of Ad26.CoV2.S through other means (for example, another mRNA booster dose).
  • •  If you are currently participating in any other research studies (other than Sisonke) that would interfere with the objectives of this study.
  • •  If you have had COVID-19 or a COVID-19 illness within 14 days of enrolment
  • •  If you have a history of heparin-induced thrombocytopenia, or thrombosis and thrombocytopenia syndrome.
  • •  If you have a history of severe adverse reaction associated with a vaccine and/or severe allergic reaction (e.g., anaphylaxis) to any component of mRNA-1273.

How to enroll?
Contact your nearest SHERPA site if you receive the SMS about the SHERPA study or click on the link

SHERPA Resources



•  Participants Information and Consent Form - An example of an information    sheet and consent form. (Please note that the information and consent process will    occur at each clinical research site)

•  SHERPA study Frequently Asked Questions

•  Participant letter -  7 Oct 2022 

Contact us


Sisonke desk: 0800 014 956


Oversight ethics committee:
South African Medical Research Council, Human Research Ethics Committee


If you have questions about this study you should first discuss them with the Clinical Research Site team, or the Sisonke Safety Desk, or the related Ethics Committee. If you have not been provided with answers to your satisfaction, you should write to the South African Health Products Regulatory Authority (SAHPRA) who provides regulatory approval for the study at: South African Health Products Regulatory Authority, Department of Health, Private Bag X828; PRETORIA; 0001