Sisonke trial shows J&J vaccine is highly effective against Delta variant

In a first, South African researchers show no booster shots are required for J&J vaccine recipients.



According to Professor Glenda Gray, who is the co-principal investigator of the Sisonke implementation study, booster shots are not required for those who have received Johnson & Johnson’s single-shot vaccine. “These results show there is no need for a booster yet,” said Gray during an address on Friday. According to Gray, in addition to demonstrating durability for eight months, the vaccine showed 71% efficacy against hospitalization and up to 96% efficacy against death. The latter was the trial’s primary endpoint, and as a result, enabled the researchers to conclude that the “vaccine protected health workers against death". The trial provides the first large-scale evidence that shows the vaccine is effective against the Delta variant, which has wreaked havoc across many parts of the world, including fuelling the third wave in South Africa.


The Sisonke study was launched in mid-February by Gray and Professor Linda-Gail Bekker, at a time when the country’s rollout was in disarray. To date, about 480,000 of the 8.3 million people who have been vaccinated in the country had received the J&J vaccine as part of the Sisonke study, which targeted healthcare workers between 17 February and 17 May. The J&J vaccine has been a key part of the country’s rollout programme. However, following reports of rare blood clots, SA temporarily paused the vaccine’s rollout earlier this year. The suspension was subsequently lifted following recommendations from the SAHPRA, which also requested stricter screening and monitoring. Further analysis of results from the Sisonke study is expected in the coming days.