A booster dose of Johnson & Johnson’s single-dose COVID-19 vaccine was 84% effective at preventing hospitalisation of South African healthcare workers who became infected as the Omicron variant spread, the Sisonke 2 study has found.
The real-world study which has not yet been peer-reviewed, was based on a second dose of the J&J vaccine administered to 69,092 workers between November 15 and December 20.
An initial course of inoculation has been shown to offer only greatly reduced protection against infection by Omicron, which has spread quickly through many countries after first being identified in late November in Southern Africa and Hong Kong, reports Reuters.
However, several studies have suggested that a booster dose provides significant protection against severe illness from the variant.
The SA study, published in MedRxiv, showed the J&J vaccine’s effectiveness at preventing hospitalisation rose from 63% shortly after a booster was administered to 84% 14 days later. Effectiveness reached 85% at one to two months after the booster shot was administered.
“It reassures us that COVID-19 vaccines continue to be effective for the purpose they were designed, which is to protect people against severe disease and death,” said Linda-Gail Bekker, the study’s co-lead investigator.
“This is yet another piece of evidence that we have not lost that impact even in the face of a very mutated variant.”
Bekker said the jury was “still out” on the issue of further boosters of the J&J shot.
“What we are showing is that two doses really restore full protection, and I don’t think we can extrapolate from this that we are going to need a third or a fourth boost at all.”
Researchers said their analysis had several limitations, including short follow-up times, which averaged eight days for healthcare workers who had received their boost within the previous 13 days, or 32 days for those boosted one to two months earlier, and which could skew overall vaccine effectiveness.
In a company statement, Dr Mathai Mammen, Global Head, Janssen Research & Development, Johnson & Johnson, said: “Data from the Sisonke 2 study confirm that the J&J COVID-19 booster shot provides 85% effectiveness against hospitalisation in areas where Omicron is dominant. This adds to our growing body of evidence which shows that the effectiveness of the J&J COVID-19 vaccine remains strong and stable over time, including against circulating variants such as Omicron and Delta. We believe that the protection could be due to the robust T-cell responses induced by the Johnson & Johnson vaccine. Furthermore, these data suggest that Omicron is not affecting the T-cell responses generated by our vaccine.”
Another SA-based study by Discovery Health, published in MedicalBrief on 15 December, showed that a first round of inoculation with two doses of Pfizer-BioNTech's COVID-19 vaccine had been less effective at keeping people infected with the virus out of hospital since the Omicron variant emerged.
Vaccine effectiveness against hospital admission in South African health care workers who received a homologous booster of Ad26.COV2 during an Omicron COVID-19 wave: Preliminary Results of the Sisonke 2 Study
Glenda Gray, Shirley Collie, Nigel Garrett, Ameena Goga, Jared Champion, Matt Zylstra, Tarylee Reddy, Nonhlanhla Yende, Ishen Seocharan, Azwi Takalani, Ian Sanne, Fatima Mayat, Jackline Odhiambo, Lesley Bamford, Harry Moultrie, Lara Fairall, Linda-Gail Bekker.
Following the results of the ENSEMBLE 2 study, which demonstrated improved vaccine efficacy of a two-dose regimen of Ad26.COV.2 vaccine given 2 months apart, we expanded the Sisonke study which had provided single dose Ad26.COV.2 vaccine to almost 500 000 health care workers (HCW) in South Africa to include a booster dose of the Ad26.COV.2. Sisonke 2 enrolled 227 310 HCW from the 8 November to the 17 December 2021. Enrolment commenced before the onset of the Omicron driven fourth wave in South Africa affording us an opportunity to evaluate early VE in preventing hospital admissions of a homologous boost of the Ad26.COV.2 vaccine given 6-9 months after the initial vaccination in HCW. We estimated vaccine effectiveness (VE) of the Ad26.COV2.S vaccine booster in 69 092 HCW as compared to unvaccinated individuals enrolled in the same managed care organization using a test negative design. We compared VE against COVID19 admission for omicron during the period 15 November to 20 December 2021. After adjusting for confounders, we observed that VE for hospitalisation increased over time since booster dose, from 63% (95%CI 31-81%); to 84% (95% CI 67-92%) and then 85% (95% CI: 54-95%), 0-13 days, 14-27 days, and 1-2 months post-boost. We provide the first evidence of the effectiveness of a homologous Ad26.COV.2 vaccine boost given 6-9 months after the initial single vaccination series during a period of omicron variant circulation. These data are important, given the increased reliance on the Ad26.COV.2 vaccine in Africa.
MedRxiv article – Vaccine effectiveness against hospital admission in South African health care workers who received a homologous booster of Ad26.COV2 during an Omicron COVID-19 wave: Preliminary Results of the Sisonke 2 Study (Open access)
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