J&J Booster Found 85% Effective Against Severe Disease During Peak Omicron Case Load

The J&J booster shot given to health care workers in South Africa between mid-Nov and mid-Dec 2021 was highly effective against Omicron infection.


A booster dose of the Johnson & Johnson COVID-19 vaccine showed 85% efficacy against COVID-19-related hospitalization among health care workers in south Africa, according to a company statement. The phase 3b Sisonke 2 trial was conducted by the South African Medical Research Council from mid-November to mid-December, a time during which the proportion of cases linked to the SARS-CoV-2 Omicron variant increased from 82 to 98% of all cases in the region.

A second separate analysis evaluating immune response to different vaccine regimens conducted by the Beth Israel Deaconess Medical Center found that a heterologous J&J booster shot generated a 41-fold increase in neutralizing antibodies against the Omicron variant and a 5-fold increase in T-cell response.

Given evidence that the omicron variant can evade neutralizing antibodies, the significant efficacy of the J&J booster against severe disease and hospitalization may be related to the increase in CD8+ T-cells generated by the vaccine, according to comments from a company research executive.

“Data from the Sisonke 2 study confirm that the Johnson & Johnson COVID-19 booster shot provides 85 percent effectiveness against hospitalization in areas where Omicron is dominant. This adds to our growing body of evidence which shows that the effectiveness of the Johnson & Johnson COVID-19 vaccine remains strong and stable over time, including against circulating variants such as Omicron and Delta,” said Mathai Mammen, MD, PhD, global head, Janssen Research & Development, LLC, Johnson & Johnson, in the press statement.

“We believe that the protection could be due to the robust T-cell responses induced by the Johnson & Johnson COVID-19 vaccine.”

Further, according to Mammen, the findings underscore the resistance of the vaccine t-cell response specifically to the Omicron variant. 

The Sisonke 2 trial (n=227 310) was conducted among healthcare workers from 350 South African vaccine centers who received the single-shot J&J COVID-19 vaccine as a primary dose. The booster increased vaccine effectiveness (VE) against hospitalization to 85%. When given at 6 to 9 months after the primary single dose, a booster was associated with an increase in VE over time, from 63% (95% CI, 31-81%) at 0-13 days, to 84% (95% CI, 67-92%) at 14-27 days, and 85% (95% CI, 54-95%) at 1-2 months post-boost.

Data from the South African study have been submitted to the pre-print server medRxiv and authors anticipate publication in peer-reviewed journals in the near future.

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