Human trial in Chinese vaccine shows promise
The result of CanSino’s Phase 1 trial, reported in The Lancet on Friday, is the first to be published in a peer-reviewed journal.
A vaccine for the coronavirus disease (Covid-19), developed by researchers at China’s CanSino Biologics was found to be safe and effective in its first test on humans, becoming the latest trial that raises hope for an early candidate that could help make people immune to the viral pandemic.
The result of CanSino’s Phase 1 trial, reported in The Lancet on Friday, is the first to be published in a peer-reviewed journal. The other experimental vaccines that have shown to work – Moderna’s and Oxford University’s -- are yet to be peer reviewed and complete data regarding their trials are unavailable.
The Chinese researchers reported that their experimental vaccine produced neutralising antibodies – the type of immune cells that kill infected cells -- and the rapid immune responses crucial for the body to mount its varied counter-attack. The trials were carried out with 108 healthy participants from Wuhan, the epicentre of the Covid-19 outbreak, who were never infected by the Sars-Cov-2, the virus which causes Covid-19.
“We found that the Ad5 vectored Covid-19 vaccine is tolerable and immunogenic in healthy adults... (it triggered) responses against Sars-CoV-2 (that) peaked at day 28 post-vaccination, and rapid, specific T-cell responses were noted from day 14 after one shot of the vaccine,” the researchers said in the paper.
One of the authors described the results as an important milestone. “The trial demonstrates the vaccine produces virus-specific antibodies and T cells in 14 days, making it a potential candidate for further investigation,” said professor Wei Chen from the Beijing Institute of Biotechnology in Beijing in a statement, news agency AFP reported.
“However ... the ability to trigger these immune responses does not necessarily indicate that the vaccine will protect humans from Covid-19,” the researcher said, adding that there was still a long way to go before “the vaccine is available to all”.
The results are based on antibody and immune cell concentrations seen within 28 days of the vaccine being given to the participants in a low, medium or a high dose. The ones given the high dose had the strongest immune response but also suffered from the most side-effects, such as high fever, fatigue and headache.
There are more than 100 vaccines in development worldwide, with at least eight having started or set to start clinical trials in humans where they are judged for how safe and effective they are. These trials will also determine which platform – the way a vaccine will train the body – works best.
CanSino’s candidate uses an inactivated adenovirus – one of the viruses that cause the common cold -- to deliver DNA into human cells, prompting them to produce a key protein found on the surface of SARS-CoV-2. This is meant to train the immune system into recognising the virus.
Moderna’s vaccine works by a code, called a messenger RNA, to prompt the body into making the same protein, the S spike protein that the Sars-Cov-2 virus uses to infect a person.
Researchers say both technologies are quickly scalable for mass development but aren’t as proven as traditional vaccines.
Clinical trials usually involve three or more phases, in which the tests are first carried out on healthy people, before being widened and randomised to rule out any externalities that could influence the findings.
In the case of the CanSino candidate, the trial has now entered the second phase. Inclusion of the people above the age of 60 and how they react to the vaccine will be crucial, the researchers noted. “In this trial, no participants were older than 60 years and only 16% were older than 50 years, providing limited information on the capability of generating a potent response in the older population. Since age has also been identified as an independent risk factor… there is a possibility that an even lower immune response might be found in the older population,” the authors warned.