New results from human trials for Covid-19 vaccines brought hope after researchers from US, Russia and UK claimed that their experimental shots are safe and induced antibodies in all trial participants.
Moderna Inc's experimental vaccine showed it was safe and provoked immune responses in all 45 healthy volunteers in an ongoing early-stage study, US researchers reported on Tuesday.
Volunteers who got two doses of the vaccine had high levels of virus-killing antibodies that exceeded the average levels seen in people who had recovered from Covid-19, the team reported in the New England Journal of Medicine.
No study volunteers experienced any serious side effects, but more than half reported mild or moderate reactions such as fatigue, headache, chills, muscle aches or pain at the injection site. These were more likely to occur after the second dose and in people who got the highest dose.
Experts say a vaccine is needed to put an end to the coronavirus pandemic that has sickened millions and caused more than 578,000 deaths worldwide.
Meanwhile, the Russian defence ministry said yesterday it had developed a "safe" coronavirus vaccine following clinical trials on a group of volunteers.
The ministry said 18 people had participated in the research and were discharged without "serious adverse events, health complaints, complications or side effects".
The results of the trials "allow us to speak with confidence about the safety and good tolerability of the vaccine", it said in a statement.
The defence ministry did not say whether the vaccine was in fact effective but a doctor working on the trials said the volunteers were now protected against the coronavirus, reports AFP.
"Their immunity is working well, antibodies are being created, they are protected against the coronavirus," researcher Svetlana Volchikhina said in a video released by the defence ministry.
Positive news on initial trials of the University of Oxford's potential Covid-19 vaccine that has been licensed to AstraZeneca could be announced as soon today, ITV's political editor Robert Peston said, citing a source.
The potential vaccine is already in large-scale Phase III human trials to assess whether it can protect against Covid-19, but its developers have yet to report Phase I results which would show whether it is safe and whether or not it induces an immune response.
The developers of the vaccine said this month they are encouraged by the immune response they have seen in trials so far and were expecting to be able to publish Phase 1 data by the end of July.
The data are expected to be published by The Lancet medical journal.
A spokeswoman for Oxford University told Reuters the team was awaiting confirmation from a scientific journal of a publication date and time for the data, but gave no further details. "(We) are not able to confirm when it will be released," she said.
Moderna was the first to start human testing of a vaccine for the novel coronavirus on March 16, 66 days after the genetic sequence of the virus was released.
Dr Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, whose researchers developed Moderna's vaccine candidate, called the results "good news," noting that the study found no serious adverse events and the vaccine produced "reasonably high" levels of virus-killing or neutralising antibodies.
"If your vaccine can induce a response comparable with natural infection, that's a winner," Fauci said in a telephone interview. "That's why we're very pleased by the results."
Moderna shares jumped more than 15% in after-hours trading on Tuesday.
The US government is supporting Moderna's vaccine with nearly half a billion dollars and has chosen it as one of the first to enter large-scale human trials. A successful vaccine could be a turning point for Cambridge, Massachusetts-based Moderna, which has never had a licensed product.
Moderna's shot, mRNA-1273, uses ribonucleic acid (RNA) - a chemical messenger that contains instructions for making proteins. When injected into people, the vaccine instructs cells to make proteins that mimic the outer surface of the coronavirus, which the body recognises as a foreign invader, and mounts an immune response against.
The results released Tuesday involved three doses of the vaccine, tested in groups of 15 volunteers aged 18-55 who got two shots, 28 days apart. The groups tested 25, 100 or 250 micrograms of the vaccine.
Adverse events after the second dose occurred in seven of the 13 volunteers who got the 25-microgram dose, all 15 participants who received the 100 microgram dose and all 14 who got the 250 microgram dose. In the highest-dose group, three patients had severe reactions such as fever, chills, headache or nausea. One of these had a fever of 103.28 Fahrenheit (39.6 C).
"We didn't see any events that are characterised as serious adverse events," said lead author Dr Lisa Jackson of Kaiser Permanente Washington Health Research Institute in Seattle, referring to reactions that require hospitalisation or result in death.
In June, Moderna said it selected the 100-microgram dose for its late-stage study to minimise adverse reactions.
At that dose, Moderna said the company is on track to deliver about 500 million doses per year, and possibly up to 1 billion doses per year, starting in 2021, from the company's internal US manufacturing site and strategic collaboration with Swiss drugmakerLonza.