LONDON – Two candidate vaccines, including a closely watched one being developed at the University of Oxford, showed positive trial results Monday against the virus that causes COVID-19, making it more likely that a safe, effective vaccine can be developed quickly.
They add to two small, previous studies on different vaccine candidates in the U.S. that also appeared to be relatively safe and to trigger appropriate immune responses in study subjects.
Early stage trials explore only safety and dosing and cannot determine a vaccine’s effectiveness, but signs indicate that all four candidate vaccines are leading to immune responses similar to those experienced by people infected with the SARS-CoV-2 virus.
About 17 candidate vaccines are being tested in people around the world.
The new results showed Oxford University and drug company AstraZeneca’s candidate vaccine, AZD-1222, led to strong immune responses for nearly two months in a trial that continues to track more than 1,000 healthy adults. A second dose, given to 10 patients, seems to have boosted their immune response further without adding significant side effects, according to a paper published Monday in The Lancet.
“I think it’s very exciting,” Barry Bloom, an immunologist and global health expert at the Harvard T.H. Chan School of Public Health, said Monday on a call with media. “The unlikely possibility that we will have vaccines ready for approval and large-scale distribution by the end of the year – which seemed utterly crazy seven months ago – may well be a real possibility.”
He and others Monday emphasized that the process is being sped up not by cutting corners on safety but by conducting research steps simultaneously that are typically done sequentially. Oxford-AstraZeneca’s trial is considered a Phase 1-2, and the pair is already getting ready to launch a large-scale Phase 3 trial within a few weeks.
Pascal Soriot, CEO of AstraZeneca, said Monday that he was pleased with the results.
“So far so good in terms of the data we’ve produced,” he said. “All this needs to translate into clinical protection. People need to be protected from infections, and that’s what we want to demonstrate in our Phase 3 program.”
Ideally, several candidate vaccines will eventually prove safe and effective. “It’s important to bet on all the technologies,” Soriot said. “Ultimately, hopefully, we have different vaccines and they may have advantages or disadvantages.”
Half the volunteers in the Oxford-AstraZeneca trial were given the SARS-CoV-2 vaccine and half were given a meningitis vaccine. The so-called AZD-1222 vaccine caused more side effects considered minor than the meningitis one, but acetaminophen relieved most of the effects, the study found.
Dr. Anthony Pollard, professor of pediatric infection and immunity at the University of Oxford and chief investigator on the study, told reporters on a call that the results were “an important milestone on the path to a development of a vaccine.”
The results in various clinical trials cannot be compared against one another, but the fact that all have shown strong immune responses suggests “that we might have multiple hits on target,” Pollard said.
He and other scientists leading the study stressed much more work needed to be done, including gauging how well the vaccine could ultimately potentially protect the general population from falling ill. Indications of that will come only with further trials on a larger group of people.
The next stage of trials in Britain will involve 10,000 people. In the U.S., 30,000 people will take part. And in Brazil and South Africa, about 7,000 people will test the efficacy and safety of the vaccine. If everything goes to plan, the vaccine could be rolled out widely by early next year, according to the Oxford Vaccine Group.
Soriot expects 50,000 will be vaccinated in clinical trials this calendar year.
“Our hope is we can start delivering vaccine (more widely) before the end of the year,” Soriot said. How soon, he said, depends on the infection rate in places where their studies are underway. Trials need enough people to become infected in order to see whether their candidate vaccine is effective.
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The Oxford-AstraZeneca vaccine uses a weakened chimpanzee cold virus to carry a protein from SARS-CoV-2 into human cells. Once there, it triggers the person’s cells to produce the spike protein found on the surface of SARS-CoV-2, causing the immune system to recognize and attack the virus.
Nearly a month after receiving a shot, 32 of 35 participants tested showed they had developed neutralizing antibodies to SARS-CoV-2 – the kind of immune response that is believed essential to provide protection. None of the participants had COVID-19, so it’s not clear whether they were actually protected against it. Only a larger, Phase 3 trial, several of which are set to start this summer, will show actual protection.
About 70% of participants in the Oxford-AstraZeneca trial suffered fatigue and headache after the AZD-1222 shot, compared with only 41%-48% of those who received the meningitis vaccine. Among the 10 people who received an extra dose of the COVID-19 vaccine, side effects were less common after the second dose.
The study’s authors recommended that the vaccine should now be tested in older adults, who have weaker immune systems and are more vulnerable to severe cases of COVID-19.
Adrian Hill, another researcher, said it would be useful to compare different vaccine results being produced in labs around the world and even to test those vaccines in the same lab. He said this would help greater understanding of how to assess the interim successes of researchers.
The second study published Monday in The Lancet looked at a Chinese vaccine candidate tested in more than 500 people, including a small number older than 55. The goal of the study was to evaluate the immune response and safety of the vaccine and determine a dose that would be used in a larger Phase 3 trial.
Of the 508 participants, 253 received a high dose, 129 received a low dose and 126 a placebo.
The Chinese vaccine candidate works almost the same way as the Oxford-Astra Zeneca one, but it uses a weakened version of the human common cold virus – rather than a chimp virus – to deliver the SARS-CoV-2 protein. Half of the trial participants were already immune to the human cold virus, which is expected to limit the vaccine’s effectiveness.
The trial found that 95% of those who received a high dose of the candidate vaccine and 91% of those who received a low dose showed an immune response 28 days after the shot. Nearly 60% showed a neutralizing antibody response, which is believed to be essential to provide protection against SARS-CoV-2.
Academic researchers who specialize in vaccine development said Monday that both studies are promising, but they’re waiting for more results before declaring victory over COVID-19.
Dr. Peter Hotez, dean of the National School of Tropical Medicine at Baylor College of Medicine, said there were “too few patients to really make conclusions.” But he said the results were promising enough to keep pursuing the vaccine in larger studies.
“Right on folks!” was how Dr. William Schaffner, a professor of preventive medicine and health policy at Vanderbilt University in Nashville, responded to the new results. Schaffner said the two studies, plus one on a vaccine candidate being developed by Moderna, have given him more confidence that it will be possible to develop an effective vaccine quickly without sacrificing safety.
“I’m clearly more confident, but my confidence is a cautious confidence,” Schaffner said. “I would like to let everyone know that I and my colleagues are going to bring our usual skepticism and hard, tough noses to this issue. We won’t let anything be released in my relatives or yours prematurely.”
Contact Weintraub at kweintraub@usatoday.
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This article originally appeared on USA TODAY: University of Oxford coronavirus vaccine candidate shows early promise