An experimental Covid-19 vaccine the University of Oxford is developing with AstraZeneca Plc showed promising results in early human testing, a sign of progress in the high-stakes pursuit of a shot to defeat the pathogen.
The vaccine, called AZD1222 did not prompt any serious side effects and elicited antibody and T-cell immune responses, according to trial results published in The Lancet medical journal, reports Reuters.
Lead author of the study, Oxford University's Andrew Pollard said: "We hope this means the immune system will remember the virus, so that our vaccine will protect people for an extended period."
"However, we need more research before we can confirm the vaccine effectively protects against SARS-CoV-2 (Covid-19) infection, and for how long any protection lasts," he said.
AstraZeneca's is among the leading vaccine candidates against a pandemic that has claimed more than 600,000 lives, alongside others in mid and late-stage trials. These include shots being developed by China's Sinovac Biotech, another from state-owned Chinese firm Sinopharm, and one from the US biotech firm Moderna.
AstraZeneca has signed agreements with governments around the world to supply the vaccine should it prove effective and gain regulatory approval. The company has said it will not seek to profit from the vaccine during the pandemic.
Researchers said the vaccine caused minor side effects more frequently than a control group, but some of these could be reduced by taking paracetamol, with no serious adverse events from the vaccine.
Stimulating production of neutralizing antibodies is considered an important early step in testing. However, it doesn't prove a vaccine will be effective. Results from testing in animals had already shown the Oxford-AstraZeneca shot provoked an immune response.
The Phase 1 trial, which took place between April 23 and May 21, involved 1,077 healthy adults aged 18 to 55 with no history of Covid-19, reports Bloomberg.
A control group were given a meningitis vaccine as a placebo and 10 participants received two doses of the shot one month apart. The vaccine caused minor side effects, which could be reduced by taking paracetamol. There were no serious adverse events from the jab.
According to head of Oxford's Jenner Institute Adrian Hill, most of the participants in the study received a single dose of vaccine and Astra will prioritize a two-shot regimen in future testing.
"It gives higher titres of antibodies, which is important going forward," he said. Moderna will also test a two-dose regimen.
AstraZeneca said in a statement that a single dose of Oxford vaccine resulted in a four-fold increase in antibodies to the virus's spike protein in 95 percent of participants one month after injection .
SARS-CoV-2 uses the spike protein to enter cells. A T-cell response was induced in all participants who got the vaccine, peaking by day 14 after injection.
"It is good, not unexpected, but good to have it confirmed. The vaccine worked and developed the all-important neutralizing antibodies, in most cases after one shot and in all cases after 2 shots," said Ian Jones, professor of biomedical sciences at the University of Reading.
The Oxford shot is close to the front of the pack and has already begun final-stage tests among the other Covid-19 vaccine researches. AstraZeneca has said it may begin delivering doses to the UK as early as September.
"We want other companies to have vaccines that work as well because the world will get more vaccine sooner," Hill said.
"We just feel there is an advantage of having both arms of the immune system stimulated well."
AstraZeneca received a boost when the US pledged as much as $1.2 billion toward development. Under its agreement with the British drugmaker, the US could begin receiving supplies as early as October. The UK has also struck a supply agreement for the shot, but on Monday it secured access to other drugmakers' experimental vaccines to hedge its bets and garner enough doses to cover its population of 66 million. The UK government secured deals with Pfizer, BioNTech and Valneva SE.
Companies and universities are relying on an array of approaches in the fight against Covid-19. The Oxford team has developed a technology that can speed up the process by using a harmless virus to carry some of the pathogen's genetic material into cells to generate an immune response. The proposed vaccine is made from a weakened version of a common cold virus that's genetically changed to make it unable to grow in humans.
Oxford has inserted genetic material from the surface spike protein of the SARS-CoV-2 virus as a way of tricking the immune system into fighting back. The platform stimulates both antibodies and high levels of killer T-cells, a type of white blood cell that helps the immune system destroy infection.
"We are very encouraged," Hill said.
While the test doesn't prove the vaccine will work, an optimistic Hill added: "I think we ae a bit more confident it should work this week than last week."