Johnson & Johnson's (J&J's) long-awaited coronavirus vaccine appears to protect against COVID-19 with just one shot — though not as strong as some two-shot rivals, it's still potentially helpful for a world in dire need of more doses.
"If it's a single-dose vaccine, then a billion vaccine doses would translate into a billion people vaccinated," Dr Dan Barouch of Harvard Medical School, who helped develop the vaccine said.
Another advantage is that the J&J shot is expected to cost as little as US$10 ($13) and doesn't require cold storage like some rival vaccines do.
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J&J said on Friday, in the US and seven other countries, the single-shot vaccine was 66 per cent effective overall at preventing moderate to severe illness, and much more protective — 85 per cent — against the most serious symptoms.
There was some geographic variation.
The vaccine worked better in the US — 72 per cent effective against moderate to severe COVID-19, compared to 57 per cent in South Africa, where it was up against an easier-to-spread mutated virus.
"Gambling on one dose was certainly worthwhile," Dr Mathai Mammen, global research chief for J&J's Janssen Pharmaceutical unit, told The Associated Press.
"The level of protection against moderate and severe COVID-19 infection was 72 per cent in the US, 66 per cent in Latin America and 57 per cent in South Africa, 28 days post-vaccination."
With vaccinations off to a rocky start globally, experts had been counting on a one-dose vaccine that would stretch scarce supplies and avoid the logistics nightmare of getting people to return for boosters.
But with some other competing vaccines shown to be 95 per cent effective after two doses, a question is whether somewhat less protection is an acceptable trade-off to get more shots in arms quickly.
The company said within a week, it will file for emergency use authorisation from the US Food and Drug Administration and expects to supply 100 million doses to the US by June.
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Level of protection
The findings are currently preliminary from a study of 44,000 volunteers that isn't completed yet.
Researchers tracked illnesses starting 28 days after vaccination – about the time when, if participants were getting a two-dose variety instead, they would have needed another shot.
After day 28, no one who got vaccinated needed hospitalisation or died regardless of whether they were exposed to "regular COVID-19 or these particularly nasty variants," Dr Mammen said.
When the vaccinated did become infected, they had a milder illness.
Defeating the scourge that has killed more than 2 million people worldwide will require vaccinating billions, and the shots being rolled out in different countries so far all require two doses a few weeks apart for full protection.
Early data is mixed on exactly how well all the different kinds work, but shots made by Pfizer and Moderna appear to be about 95 per cent protective after the second dose.
But amid shortages, some countries have advised delaying the second dose of certain vaccines with little data on how that would affect protection.
"A vaccine that's inexpensive, that's a single dose, and that has no cold chain requirements — that's pretty good," Dr Anthony Fauci, director of the US National Institute of Allergy and Infectious Diseases told CNN.
Dr Fauci said the results would look even better if J&J did not have to compete against the 94 per cent and 95 per cent efficacy seen in trials of the Pfizer and Moderna vaccines.
"You know what the problem is? If this were out there and we didn't have the Moderna 94-95 per cent — we would have said wow, a 72 per cent effective vaccine that's even more effective against severe disease is really terrific," he said.
"It has a very good efficacy against severe disease."
How is it made?
All COVID-19 vaccines train the body to recognise the new coronavirus, usually by spotting the spikey protein that coats it. But they're made in very different ways.
J&J's shot uses a cold virus like a Trojan horse to carry the spike gene into the body, where cells make harmless copies of the protein to prime the immune system in case the real virus comes along.
Rival AstraZeneca makes a similar cold virus vaccine that requires two doses.
Both the AstraZeneca and J&J vaccines can be stored in a refrigerator, making them easier to ship and to use in developing countries than the frozen kind made by Pfizer and Moderna.
It's not clear exactly how well the AstraZeneca version, being used in Britain and several other countries, works.
Tests in Britain, South Africa and Brazil suggested two doses are about 70 per cent effective although there are questions about how much protection older adults get. An ongoing US study may provide more information.
J&J said its vaccine works consistently in a broad range of people: A third of participants were over age 60, and more than 40 per cent had other illnesses putting them at risk of severe COVID-19, including obesity, diabetes and HIV.
J&J said the vaccine is safe, with reactions similar to other COVID-19 shots such as fever that occur when the immune system is revved up.
While it released few details, the company said there were no serious allergic reactions.
But occasionally other COVID-19 vaccines trigger such reactions, which can be reversed if promptly treated – and authorities have warned people to be on the lookout regardless of which type of vaccine is used.
J&J had hedged its bets with a study of a two-dose version of its vaccine, which is still underway.
Friday's interim results come on the heels of another vaccine in final testing.
Novavax reported this week that its vaccine appears 89 per cent effective in a UK study and that it also seems to work, though not as well, against new mutated versions of the virus circulating in Britain and South Africa.
A larger study in the US and Mexico is still enrolling volunteers.
