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Data from the SISONKE Study confirms good safety profile of the single-shot Johnson and Johnson COVID-19 vaccine

SisonkeCape Town | Data from the Sisonke Study has confirmed that the single-dose Ad26.COV2.S vaccine (Johnson and Johnson COVID-19 vaccine) had a good safety profile. This follows the publication of the Sisonke safety report in this week’s issue of PLoS Medicine, a peer-reviewed weekly medical journal covering the full spectrum of the medical sciences.

These latest developments support the continued use of this vaccine in large COVID-19 vaccination rollout programmes.

Led by the South African Medical Research Council (SAMRC) and conducted in collaboration with the National Department of Health, the Sisonke study aimed to assess the effectiveness and safety of the JnJ vaccine among 477,234 healthcare workers across all South African provinces who received the vaccine between 17 February and 17 May 2021. The effectiveness results have since been published in The LANCET and the New England Journal of Medicine (NEJM)  – to date this is the largest safety analysis of the JnJ COVID-19 vaccine from a low- or middle-income country.

Adverse events, serious adverse events, and adverse events of special interest were collected through self-reports and active case finding. An adverse event is any untoward medical occurrence in a study participant who has received a vaccine regardless of whether it is caused by the vaccine or not. Reactogenicity events, which are expected to occur after vaccination are also included as adverse events.

Overall, the occurrence of adverse events was low. The majority of adverse events reported, about 81%, were reactions commonly experienced after vaccination (reactogenicity). These self-limiting reactogenicity events occur soon after vaccination and include symptoms such as pain, headache, fever, chills and rigors, muscle aches and weakness, joint pains, tiredness. Serious adverse events were rare (1.4% of all adverse events) and occurred at lower than the expected population rates and were successfully managed with prompt identification. There were two serious adverse events known as thrombosis with thrombocytopenia syndrome (a blood clotting disorder) in two participants both of whom recovered fully. Four participants had an allergic reaction deemed an anaphylaxis to the vaccine, and all recovered fully. In additional analysis, the Sisonke study did not identify any unexpected deaths in the vaccinated population compared to the general population.

Dr Simba Takuva, lead medical monitor on the study said vaccination is very effective at preventing COVID-19-related severe disease, hospitalization and death. “The Sisonke analysis confirms the safety of the Ad26.COV2.S vaccine at population level,” he said. Emphasizing the importance of vaccine safety, SAMRC President and CEO, Professor Glenda Gray who is also the Sisonke Study’s Co-Principal Investigator, said “Data on the safety of vaccines are critical for public trust. Our data from this large data-set help inform the use of this vaccine in Africa”.

Overall, the Sisonke Study results provide additional real-world evidence that the JnJ vaccine is safe, well tolerated, and that its benefits far outweigh the risks, thus supporting its continued use in COVID-19 vaccination programmes.


About the Sisonke Study:

The Sisonke study is a collaboration between the National Department of Health, South African Medical Research Council, Desmond Tutu Health Foundation, CAPRISA, Janssen and Johnson & Johnson. This open label, single-arm Phase 3b vaccine clinical trial of the investigational single-dose Janssen COVID-19 vaccine candidate aims to monitor the effectiveness of the investigational single-dose Janssen vaccine candidate at preventing severe COVID-19, hospitalizations and deaths among healthcare workers as compared to the general unvaccinated population in South Africa. Health workers who received a Sisonke vaccine will be followed for a period of two years.


The Sisonke Study team acknowledges the SAMRC for the sponsorship and oversight, Janssen Vaccines and Prevention for the supply and transportation of the study product to South Africa, Right to Care for providing the safety monitoring and reporting infrastructure, Discovery Health for supporting data acquisition, and the National Department of Health. We thank all the healthcare workers who participated in this study, the investigators and staff members at the vaccination centers and clinical research sites, the protocol team, the protocol safety review team, and the members of the Independent Data and Safety Monitoring Committee.

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Tendani Tsedu
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