New York, January 31 (RHC)-- Johnson & Johnson’s long-awaited vaccine appears to protect against COVID-19 with just one shot – not as strong as some two-shot rivals but still potentially helpful for a world in dire need of more doses.

J&J announced that in the United States and seven other countries, the single-shot vaccine was 66 percent effective overall at preventing moderate to severe illness, and much more protective – 85 percent – against the most serious symptoms.  There was also some geographic variation.  The vaccine worked better in the U.S. — 72 percent effective against moderate to severe COVID-19 – compared with 57 percent 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 news agency.  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 percent effective after two doses, at question is whether somewhat less protection is an acceptable tradeoff to get more shots in arms quickly.  The company said within a week, it will file an application for emergency use in the U.S., and then abroad.  It expects to supply 100 million doses to the US by June, and expects to have some ready to ship as soon as authorities give the green light.

These are preliminary findings from a study of 44,000 volunteers that are not 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 or these particularly nasty variants”, Mammen said.  When the vaccinated did become infected, they had a milder illness.

Defeating the scourge that has killed more than two 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 percent 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.

All COVID-19 vaccines train the body to recognise the new coronavirus, usually by spotting the spikey protein that coats it. But they are 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.