Potential Coronavirus vaccines head towards crucial third step

The race for a Covid-19 vaccine has taken on critical importance as the disease continues to charge through the global population, with almost 15 million confirmed cases and nearly 615,000 deaths.
The world hopes a vaccine can be a silver bullet out of the crisis, and new results from some of the teams leading development are showing early promising signs. But the real test lies ahead in the final-phase trials, experts say.
The new data out on Monday includes a vaccine candidate produced by a team at Oxford University, working in partnership with British firm AstraZeneca.
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The candidate was safe and induced strong immune responses in combined phase-one and phase-two trials, according to a study published in The Lancet scientific journal.
A candidate from Chinese biopharmaceutical company CanSino Biologics, produced in collaboration with the Chinese military, was also found to be safe and able to create an immune response in most candidates, according to results from phase-two trials, also published in The Lancet on Monday.
A second set of preliminary results for a vaccine candidate produced by United States company Pfizer and German partner BioNTech were released as non-peer-reviewed data on Monday. This candidate also produced a strong antibody response.
While all three candidates created some side effects, none were severe or life-threatening.
Mike Ryan, executive director of the World Health Organisation’s Health Emergencies Programme, welcomed the data release as “good news” in a press briefing on Monday. But he warned that “there is a long way to go” as candidates moved into “real-world, larger phase trials.”
Early-stage trials look to evaluate issues such as the safety, dosing and side effects of a vaccine candidate. They also check for the effectiveness in producing a potentially virus-neutralizing immune response.
Phase-three trials, the last phase before possible regulatory approval, continue to monitor for safety while evaluating how effective a vaccine is at protecting people from getting sick in their daily lives. These trials often aim to include people from diverse demographics and can have sample sizes in the tens of thousands.
Immunologist Kylie Quinn, a vice-chancellor’s research fellow at RMIT University in Australia, said the latest round of results, indicating that candidates were producing the immune response researchers were looking for, marked a “crucial hurdle” on the path towards a vaccine.
“When they can get over that hurdle, then it makes it worthwhile to do a phase-three trial to really test if (the candidates) can work in a general population,” she said.
But tempering expectations is also essential, Quinn said, as approved vaccines might not be able to protect people from the disease completely. But they could still “provide benefits in reducing disease severity and the transmission of the virus from person to person.”
Several phase-three trials are already ongoing or expected to begin this month. Predictions about when potentially approved vaccines could be ready for market range from the end of this year to mid-2021.
Two vaccine candidates produced by Chinese teams are in final-phase trials, with one by Chinese firm, Sinopharm, in trials in Abu Dhabi, and another by Sinovac Biotech’s being the subject of trials in Brazil. CanSino earlier this month said that it was in talks for its overseas phase-three trials.
Low numbers of infections in China have made clinical trials in the country difficult.
The vaccine candidate from Oxford University and AstraZeneca is already in phase-three trials in Brazil and South Africa, with enrolment open in the US for a large-scale test.
US company Moderna, working with the US National Institute of Allergy and Infectious Diseases, plans to start final-phase trials at the end of the month. The team last week published its phase-one results showing its product was safe and produced immune responses.
The Pfizer and BioNTech candidate may also enter late-stage testing this month, pending approval.
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