FILE - A member of the Philadelphia Fire Department prepares a dose of the Johnson & Johnson COVID-19 vaccine at a vaccination site setup in Philadelphia, on March 26, 2021. A government advisory panel is meeting Thursday, Dec. 16, to determine if any restrictions are needed to the Johnson & Johnson COVID-19 vaccine because of rare but serious blood clots. (AP Photo/Matt Rourke, File)

By Ashley Gallagher

Results of a separate analysis demonstrate that Johnson & Johnson’s booster generated a 41-fold increase in neutralising antibodies and a 5-fold increase in T-cells against omicron.

Johnson & Johnson (J&J) has announced preliminary results from the South African phase 3b Sisonke study, which showed that a homologous, or same vaccine, booster shot of the J&J COVID-19 vaccine demonstrated about 85% effectiveness against COVID-19-related hospitalisation.

The study, conducted by the South African Medical Research Council (SAMRC), showed that the booster shot reduced the risk of hospitalisation from COVID-19 among health care workers in South Africa after omicron became the dominant variant.

During the study months from mid-November 2021 to mid-December 2021, the frequency of the omicron variant increased to 98% from 82% of COVID-19 cases in South Africa, as reported by GISAID, which provides COVID-19 data. The results of a second, separate analysis of the immune response to difference vaccine regimens show that a heterologous, or a different type, booster of the J&J COVID-19 vaccine in individuals who initially received the BNT162b2 mRNA, or the Pfizer vaccine, generated a 41-fold increase of neutralizing antibodies by 4 weeks following the booster, as well as a 5-fold increase in CD8+ T-cells to Omicron by 2 weeks.

A homologous boost with the Pfizer vaccine generated a 17-fold increase in neutralizing antibodies by 4 weeks following the shot and a 1.4-fold increase in CD8+ T-cells by 2 weeks.

The increase in CD8+ T-cells generated by the J&J vaccine may be key to explaining the high levels of effectiveness against severe COVID-19 disease and hospitalisation, because the omicron variant has been shown to escape neutralizing antibodies.

“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,” Mathai Mammen, MD, PhD, global head of Janssen Research & Development, LLC, at J&J, said in a statement.

“We believe that the protection could be due to the robust T-cell responses induced by the Johnson & Johnson COVID-19 vaccine. Furthermore, these data suggest that omicron is not affecting the T-cell responses generated by our vaccine,” Mammen said.

The data have been submitted to the pre-print server medRxiv with anticipation of publication in peer-reviewed journals.

Data from the Sisonke 2 trial showed that when a booster shot was administered 6 to 9 months after the primary single dose, vaccine effectiveness increased over time from 63% at 0 to 13 days, to 84% at 14 to 27 days and 85% at 1 to 2 months post-boost.

Sisonke 2 was conducted in approximately 350 vaccination centres across all 9 provinces of South Africa.

The trial commenced just before the onset of the omicron wave, which allowed investigators to evaluate the effectiveness specifically against the omicron variant.

“Even before you factor in the increased infectiousness of omicron, we have to remember that health care workers on the frontlines are at a greatly increased risk of being affected by COVID-19 in the first place,” Glenda Gray, MBBCH, FCPaed (SA), president and CEO of the SAMRC, said in the statement. “We are therefore encouraged to see that boosting with the J&J COVID-19 vaccine regimen provides strong protection in a challenging real-world setting where there is an elevated risk of exposure, not just to COVID-19, but to the highly transmissible Omicron variant.” –

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