A second dose of the Johnson & Johnson vaccine protected health-care workers in the Sisonke study from severe disease and hospitalisations, by up to 82% in the first two months, compared to unvaccinated populations.

The study, which is one of the first real world studies on vaccine effectiveness against the Omicron variant, was published in the New England Journal of Medicine earlier this month.

Senior author and Sisonke Co-Lead Professor Linda-Gail Bekker said the vaccines available in South Africa’s rollout are proving to offer protection against the Omicron variant.

“There is great utility of a single dose of the J&J vaccine in emergency situations, but it is very reassuring in this study to see two doses of J&J performs equally well to two doses of the Pfizer vaccine,” she said.

Earlier this year, the Sisonke team published a study in the Lancet, showing that one dose of the J&J vaccine was up to 83% effective in preventing Covid-19 deaths and 67% effective in preventing Covid-19 related hospitalisations.

In the latest study, researchers examined the effectiveness of a second J&J dose in health-care workers.

More than 240 000 Sisonke study participants received their second jabs in November and December 2021, which was around the same time when the Omicron variant caused the fourth wave in the country.

The study defined severe Covid-19 as a patient having to be hospitalised or admitted to an intensive care unit (ICU).

Lead author of the study and Co-Principal Investigator Professor Glenda Gray said that evaluating the vaccine among health-care workers was critical, as they are seven times more likely to have severe Covid-19 infection.

“The Sisonke study has contributed globally to data, on both safety and effectiveness, even against current variants of concern, and forms the backbone of the rollout of the Ad26.COV.2 vaccine,” she said.

Since the rollout began to the general public in May last year, a total of 35.4 million vaccines have been administered to about 19.7 million people in South Africa.

More than 8.6 million Johnson & Johnson vaccines have been administered in South Africa, while 26.8 million shots of the Pfizer vaccine two-dose regimen have been administered.

The Sisonke study shows real world vaccine effectiveness against Omicron. https://t.co/mqDUVesOjR pic.twitter.com/vgcgJfBp3W
— SAMRC (@MRCza) May 16, 2022

#sisonke-trial

Second jab of J&J is 82% effective against severe disease, says Sisonke study