Preclinical tests on non-human primates found that the potential vaccine, when given at a sufficient dose, could provide “complete protection against Sars-CoV-2” strains in different countries with minimal side-effects, Qin and his team wrote in a non-peer reviewed paper released on preprint service medRxiv.org on Sunday. Sars-CoV-2 refers to the virus that causes Covid-19.

Qin’s team based their potential vaccine on a strain isolated from a patient in Zhejiang. The province in eastern China has not been badly hit by the virus compared to other places – it has a population of nearly 60 million, but has reported about 1,200 cases and one death.

They then sought to test whether a vaccine based on this strain would work on others. According to their paper, the team analysed the whole genome sequence of the coronavirus in a global database, identifying major clusters of mutated strains across the world. They then isolated the strains that had the most typical mutations, based on 10 recently infected patients from China, Italy, Britain, Switzerland and Spain.

Tests on macaques had encouraging results – they developed antibodies to a level equivalent to those infected by the virus, the researchers said. The vaccinated macaques were then given “strains circulating worldwide” but the pathogens did not affect them, according to the paper.

The vaccine candidate’s safety and effectiveness is now being put to the test in human trials, but there is also the question of whether it can provide immunity for multiple strains.

The team did not have a strain from a patient in the United States, for instance, so instead used one from a Chinese patient that had a mutation similar to those prevalent in North America. The researchers also noted that they had not included new mutations from less reported areas including Latin America, the Middle East and India.

Qin did not immediately respond to a request for comment.

Coronavirus: vaccine with ‘incomplete’ immunity could offer a solution to pandemic, experts say

One of the study authors, Gong Xuejie from Sinovac Biotech, a Beijing-based company involved in the project, said the first volunteers in the trial were all healthy adults aged between 18 and 59.

“Safety checks on the first day after the vaccinations have been completed and preliminary results show the vaccine [candidate] is safe,” Gong told Shanghai news website Thepaper.cn on Friday.

She said two more clinical trials would follow and they would be larger scale and include children and elderly people but there was “no definite schedule”.

The potential vaccine is one of at least five being developed in China, and it is estimated that more than 70 are being developed around the world. Two other vaccine candidates are being tested on humans in China, and at least two more are undergoing clinical trials in the United States.

Coronavirus: green light for human trials on two more Chinese vaccine hopefuls

Experts say a vaccine could still be more than a year away, but a Chinese health official on Monday said the government may consider approving one earlier for emergency use.

Gao Fu, director of the Chinese Centre for Disease Control and Prevention, told official newspaper Beijing Daily that if the pandemic worsened, a vaccine candidate “may be given to some people at the end of the year, such as medical personnel”.

“This must be for use in an emergency situation, not for ordinary healthy people,” Gao said.