J&J's single-dose COVID-19 vaccine 66% effective

Johnson & Johnson reported top-line results Friday showing that its investigational single-dose vaccine candidate Ad26.COV2.S met all primary and key secondary endpoints of the Phase III ENSEMBLE study, with an overall efficacy rate of 66% at preventing moderate-to-severe COVID-19, 28 days after vaccination. The interim analysis also demonstrated that the vaccine was 85% effective when it came to preventing severe disease, while it completely protected against COVID-related hospitalisation and death, 28 days post-vaccination.

Johnson & Johnson said it plans to seek US emergency-use authorisation for the vaccine, which employs its AdVac viral vector technology, in early February, adding it expects to have product available to ship immediately after receiving the green light. "The potential to significantly reduce the burden of severe disease, by providing an effective and well-tolerated vaccine with just one immunisation, is a critical component of the global public health response," remarked Paul Stoffels, chief scientific officer at Johnson & Johnson.

ENSEMBLE was launched in September, and assessed how well Ad26.COV2.S, also known as JNJ-78436735, could protect against moderate-to-severe COVID-19 versus placebo at 14 days and 28 days after one dose, the study's co-primary endpoints. The trial was conducted at sites in the US, South Africa and Latin America. The interim data are based on 43,783 participants 18 years and older accruing 468 symptomatic cases of COVID-19, with Johnson & Johnson saying the vaccine demonstrated onset of protection as early as day 14. The drugmaker noted that protection was "generally consistent" across race and age groups, including adults over 60 years of age, while efficacy against severe disease increased over time.

Efficacy varied by region

The study also shed light on the potential of Ad26.COV2.S to confer immunity against emerging viral mutations. Johnson & Johnson said the level of protection against moderate-to-severe COVID-19 infection was 72% in the US, dropping to 66% in Latin America and 57% in South Africa. "What we are learning is there is different efficacy in different parts of the world," Stoffels said, although he suggested that the vaccine was 89% effective at preventing severe disease in participants in South Africa. Johnson & Johnson noted that in South Africa, 95% of cases of COVID-19 in the trial were due to infection with a SARS-CoV-2 variant from the B.1.351 lineage, which has shown evidence of being less susceptible to previous antibodies.

Meanwhile, the study's data and safety monitoring board did not report any significant safety concerns related to Ad26.COV2.S. The company said its vaccine was "generally well tolerated," with fever rates at 9% overall, while serious cases of fever only occurred at a rate of 0.2%. Overall, serious adverse events were more frequent among participants who received placebo, and no cases of anaphylaxis were reported. Results showed that there were no deaths related to COVID-19 in the vaccine group, while five deaths in the placebo group were related to the coronavirus. Johnson & Johnson said the data will be submitted to a peer-reviewed journal in the coming weeks.

Advantages over Pfizer, Moderna vaccines

The two coronavirus vaccines currently authorised for emergency use in the US are Pfizer and BioNTech's BNT162b2 and Moderna's mRNA-1273. While both mRNA vaccines have shown roughly 95% efficacy rates against symptomatic disease, as well as high levels of protection against severe illness, they also have drawbacks, including more complex storage requirements and the fact that they have to be administered as two doses. By contrast, Johnson & Johnson says its single-dose vaccine can remain stable for two years at -20°C, at least three months of which can be at temperatures of 2°C to 8°C. The company noted that it also plans to ship Ad26.COV2.S using the same cold chain technologies it already uses to transport other medicines.

Moreover, the Pfizer/BioNTech and Moderna vaccines underwent clinical testing last summer prior to the emergence of COVID-19 variants. Mathai Mammen, global head of R&D at Johnson & Johnson's Janssen unit, remarked "they did run the vaccine at a period that was simpler… These variants are particularly tricky as they can be more virulent [and] a little bit harder to protect from."

Moderna said recently that it is weighing different strategies on how to combat emerging mutations of SARS-CoV-2, including developing an updated version of mRNA-1273 that would be protective against the South African strain. Novavax also plans to begin testing candidates against new strains in the second quarter, after data from two trials showed its COVID-19 vaccine NVX-CoV2373 was more than 89% effective against the fast-spreading UK variant, but much less so against the South African strain.

100 million doses by mid-year

Meanwhile, Johnson & Johnson anticipates being able to honour its 2021 supply commitments, with a spokesman saying the company expected to supply 100 million doses of Ad26.COV2.S to the US government in the first half of the year. According to a Government Accountability Office report released this week, Johnson & Johnson will deliver about 2 million doses of its COVID-19 vaccine when it receives an emergency-use authorisation in the US.

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