J&J’s COVID-19 Vaccine 66% Effective in Moderate, Severe Cases

Johnson & Johnson recently announced that a single-dose of its COVID-19 vaccine candidate, Ad26.COV2.S, was 66 percent effective at preventing moderate to severe coronavirus in a Phase 3 clinical trial. 

The Phase 3 ENSEMBLE trial enrolled 43,783 participants, of which 468 had symptomatic cases of COVID-19. The co-primary endpoints were measured 14 and 28 days after vaccination.

Efficacy against the virus increased over time, with no cases in vaccinated participants reported after Day 49, the company said. 

Ad26.COV2.S also significantly helped infected individuals requiring medical intervention, including hospitalization, ICU admission, mechanical ventilation, and extracorporeal membrane oxygenation, with no reported cases among participants who received the vaccine.

“These topline results with a single-shot COVID-19 vaccine candidate represent a promising moment. The potential to significantly reduce the burden of severe disease, by providing an effective and well-tolerated vaccine with just one immunization, is a critical component of the global public health response,” Paul Stoffels, MD, vice chairman of the executive committee and chief scientific officer at Johnson & Johnson, said in the announcement. 

“A one-shot vaccine is considered by the World Health Organization to be the best option in pandemic settings, enhancing access, distribution and compliance. It offers the hope of helping ease the huge burden placed on healthcare systems and communities,” Stoffels continued. 

The company noted that the safety profile was overall consistent with other vaccine candidates using Janssen’s AdVac technology. Any serious adverse events reported were more notable in participants who received placebo as compared to the vaccine candidate.  

Overall, Ad26.COV2.S was 85 percent effective in preventing severe disease across all regions studied. 

But while the vaccine was 72 percent effective in the US and 66 percent effective in Latin America, it was just 57 percent effective in South Africa, where a more contagious strain has been spreading. 

Ad26.COV2.S is not as effective as its competitors, including Pfizer-BioNTech’s COVID-19 vaccine, BNT162b2, and Moderna’s vaccine, mRNA-1273, which were both found to be over 90 percent effective in clinical trials in November. 

But experts have noted several advantages of the vaccine candidate compared to others being tested in clinical trials, including that it is a single dose and does not need to be frozen, which could ease manufacturing and distribution concerns. 

In mid-January, The New England Journal of Medicine released data from an interim Phase 1/2a study ofAd26.COV2.S, which showed that the candidate provided an immune response that lasted for at least 71 days in participants 18 to 55 years of age. 

Specifically, after a single vaccination, neutralizing antibodies against COVID-19 were detected in over 90 percent of study participants at Day 29 and 100 percent of participants at Day 57.

The ongoing randomized, double-blind trial aims to evaluate the safety, reactogenicity, and immunogenicity of Johnson & Johnson’s COVID-19 vaccine candidate at two dose levels, administered intramuscularly as single-dose or two-dose schedules, eight weeks apart. 

The full study results are expected later this year. 

“These results are a testament to the extraordinary efforts of everyone involved in our COVID-19 vaccine candidate clinical program, and we are extremely grateful to the clinical trial staff and trial participants for their invaluable contributions,” Mathai Mammen, MD, PhD, global head of Janssen research & development, said in the recent announcement. Janssen is a division of Johnson & Johnson.

“Changing the trajectory of the pandemic will require mass vaccination to create herd immunity, and a single-dose regimen with fast onset of protection and ease of delivery and storage provides a potential solution to reaching as many people as possible,” Mammen concluded.