Johnson & Johnson Booster 85% Effective Against Omicron

Source: Freepik

A South African trial reported Johnson & Johnson booster as 85% effective at preventing Omicron hospitalizations.

Recently, researchers at the South African Medical Research Council conducted a trial evaluating the effectiveness of the Johnson & Johnson booster against Omicron. During the trial, Omicron cases increased from 82 to 98% in South Africa. Thus, the study provides evidence on vaccine efficacy from a period of high Omicron circulation.

The trial, called the Sisonke 2 study, administered a single J&J booster dose to healthcare workers 6-9 months after their primary dose. Researchers then compared hospitalization rates between the 69,000 boosted healthcare workers and unvaccinated individuals. Two months after the booster dose, vaccine effectiveness for hospitalization increased to 85%. The results of the study are available on the pre-print server medRxiv.

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.

Dr. Mathai Mammen, Johnson & Johnson

Generally, healthcare workers are at an increased risk of COVID-related hospitalization and deaths. Moreover, the continuously mutating virus poses further risks to these frontline workers. Therefore, the Sisonke 2 trial provides encouraging data on the effectiveness of the COVID vaccine against the new coronavirus variants.

This data should reassure healthcare workers who have not taken their booster to get vaccinated as soon as possible.

Dr. Nicholas Crisp, Deputy Director General of the South African National Department of Health

Although Johnson & Johnson has shown promising results in clinical trials, the adenovirus vaccine has also been associated with some adverse reactions. Multiple reports of vaccine-induced immune thrombotic thrombocytopenia (VITT) have occurred among vaccine recipients. Thus, the increased risk of blood clots has led the CDC to recommend Pfizer and Moderna shots over Johnson & Johnson. However, the pharmaceutical company has maintained that their vaccine remains an effective and safe candidate against COVID-19.


Gray, Glenda E, et al. “Vaccine Effectiveness against Hospital Admission in South African Health Care Workers Who Received a Homologous Booster of ad26.cov2 during an Omicron covid19 Wave: Preliminary Results of the Sisonke 2 Study.” 2021, doi:10.1101/2021.12.28.21268436.


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