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Data suggest Janssen single-dose vaccine has overall efficacy of 66%

The headline results from the latest Phase III trial of Janssen’s single-dose vaccine indicate that it is highly effective at preventing both moderate and severe COVID-19.

Data from ENSEMBLE, a randomised, double-blind, placebo-controlled, Phase III trial of Janssen’s single-dose vaccine, suggest an overall efficacy of 66%. The trial, which was launched in September 2020 and conducted in eight countries included 43,783 participants, of whom 14,672 (14%) were 60 years and older and 55% were male. As the trial was conducted across several countries, it enabled the inclusion of different ethnicities e.g., 9% were Black/African Americans and 3% Asian. In addition, 41% of participants had co-morbidities linked to an increased risk of progression to more severe disease including obesity (28.5%), type 2 diabetes (7.3%) and hypertension (10.3%). The study had a co-primary endpoint of COVID-10 cases at 14- and 28-days post-vaccination.

While the study results are not yet published, a press release by the parent company of Janssen, Johnson & Johnson, provides an overview of the study results and reports that the onset of protection was observed as early as day 14. Moreover, the level of protection against moderate to severe COVID-19, defined to include for example, evidence of pneumonia, deep vein thrombosis, shortness of breath, was 72% in the US, 66% in Latin America and 57% in South Africa, 28 days post-vaccination. Interestingly, the vaccine appeared to be effective against the COVID-19 variant, B.1.3521 which was first detected in South Africa.

The single-dose vaccine was also able to protect against severe COVID-19, defined to include: signs consistent with severe systemic illness, admission to intensive care and respiratory failure. In patients meeting these criteria, the vaccine demonstrated an 85% efficacy across all regions studied and that this efficacy increased over time so that there were no severe cases among vaccinated individuals reported after day 49. The vaccine also demonstrated complete protection against COVID-19-related hospitalisation and deaths, 28 days after vaccination. Protection was reported as being consistent across race, age groups (including those over 60 years of age, for which there were 13,610 participants). The press release also reports that the company intends to apply for emergency use authorisation in the US in early February 2021.

Johnson & Johnson press release.

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