Johnson & Johnson's single-dose vaccine is 72 per cent effective in preventing Covid-19 in the United States, but a lower rate of 66 per cent was observed globally in the large trial conducted across three continents and against multiple variants the drugmaker has confirmed today.
In the trial of nearly 44,000 volunteers, the level of protection against moderate and severe Covid-19 was 66 per cent in Latin America and just 57 per cent in South Africa, where a new variant of the virus is circulating.
Those results compare to the high bar set by two authorised vaccines from Pfizer Inc/BioNTech and Moderna, which were around 95 per cent effective in preventing symptomatic illness in pivotal trials when given in two doses. Those trials, however, were conducted mainly in the United States and before the broad spread of new variants now under the spotlight.
J&J's main study goal was the prevention of moderate to severe Covid-19, and the vaccine was 85 per cent effective in stopping severe disease and preventing hospitalisation across all geographies and against multiple variants 28 days after immunisation.
That level of prevention "will potentially protect hundreds of millions of people from serious and fatal outcomes of Covid-19," Dr Paul Stoffels, J&J's chief scientific officer, said in a statement.
The company plans to seek emergency use authorization from the US Food and Drug Administration next week.
Unlike the Pfizer/BioNTech and Moderna vaccines, J&J's does not require a second shot weeks after the first or need to be kept frozen, making it a strong candidate for use in parts of the world with weak transportation infrastructure and insufficient cold storage facilities.
Several studies have emerged this month showing that a South African variant has mutated in areas of the virus that are key targets of vaccines, reducing their efficacy.
"What we are learning is there is different efficacy in different parts of the world," Dr Stoffels said in a telephone interview.
Importantly, though, in a sub-study of 6,000 volunteers in South Africa, Dr Stoffels said, the J&J vaccine was 89 per cent effective at preventing severe disease. Ninety-five per cent of cases in the South Africa portion of the trial were infections with the South African variant.
A mid-stage trial of a Novovax Inc coronavirus vaccine in South Africa also showed lower efficacy in the country. It proved to be 60 per cent effective among volunteers who did not have HIV. In a separate, late-stage trial in the UK, the vaccine was 89.3 per cent effective.
In the J&J trial, which was conducted in eight countries, 44 per cent of participants were from the United States, 41 per cent were from Central and South America and 15 per cent were from South Africa. Slightly more than a third of the volunteers were over 60.
There were no serious adverse events among those who received the shot, the company said. Full results will be published in a peer-reviewed journal.
J&J's vaccine uses a common cold virus known as adenovirus type 26 to introduce coronavirus proteins into cells in the body and trigger an immune response.
The Pfizer/BioNTech and Moderna vaccines use a new technology called messenger RNA (mRNA) that requires it to be stored in a freezer.
J&J has said it plans to deliver 1 billion doses in 2021 and will produce the vaccine in the United States, Europe, South Africa and India.