Two potential coronavirus vaccines prove safe and effective in humans

Vaccines being developed in Britain and China have proven both safe and effective in developing immune resistance to the virus that causes Covid-19 in humans, according to research published Monday. Researchers warned Tuesday that there were no guarantees of availability this year.

Results of two early-stage trials of coronavirus candidate vaccines published in medical journal The Lancet on Monday showed signs of training the immune system to recognise and fight the virus without serious side effects. REUTERS - Dado Ruvic

Results of two early-stage trials of coronavirus candidate vaccines published in medical journal The Lancet on Monday showed signs of training the immune system to recognise and fight the virus without serious side effects.

Just added to The Lancet's #COVID19 Resource Centre—Safety and immunogenicity of two COVID-19 vaccine trials: ChAdOx1 https://t.co/qzlBcVGaGj and adenovirus type-5 vectored https://t.co/X0TmwFTxBd plus linked Comment https://t.co/wAfiTSqAEU pic.twitter.com/3eEANYlvpa

— The Lancet (@TheLancet) July 20, 2020

One of the vaccines is being developed at Oxford University in the UK and the other at a centre in Wuhan, China, the epicentre of the first Covid-19 epidemic in January.

Both found production of neutralising antibodies and T-cell responses in the majority of test subjects, with side effects including mild fatigue, headaches and pains treatable by common painkillers. 

The journal noted the studies now have to be tested on larger populations in order to better understand their effectiveness and safety, but that the early similar results were promising.

Several steps before widespread availability

Sarah Gilbert, part of the team working at Oxford, warned Tuesday there was no certainty as to when the vaccine would be widely available.

“The end of the year target for getting vaccine rollout, it’s a possibility, but there’s absolutely no certainty about that,” she told BBC Radio. 

The vaccine needs to work in late-stage trials involving thousands of subjects, there need to be large quantities manufactured and regulators would have to agree quickly to license it for emergency use. 

“All of these three things have to happen and come together before we can start seeing large numbers of people vaccinated,” Gilbert said. 

Antibodies in 90 percent of participants

The study at Oxford involved 1,077 healthy adults aged 18-55. It found neutralising antibodies generated in more than 90 percent of participants and T-cell responses induced in all of them.

The vaccine uses a weakened version of a common-cold virus that encodes instructions for making proteins from the SARS-CoV-2 virus, which causes the coronavirus disease, to build immunity.

The World Health Organization previously said the Oxford vaccine, which is licensed to British-Swedish multinational company AstraZeneca, was one of the leading candidates.

Late stage trials are currently underway in Britain, Brazil and South Africa and are due to start in the United States, with Mexico also in talks to run trials. Data is expected by August or September, with first doses expected between September and October.

Safety for elderly to be confirmed

The Chinese study involved 508 participants aged 18-83, and reported antibodies in 85 percent and T-cell responses in 90 percent of participants.

Authors of the Chinese study said the safety of the vaccine would need to be verified for elderly patients – the age group most vulnerable to Covid-19. 

The vaccines’ staying power is not yet known, nor is their effectiveness for specific groups including the elderly, people with chronic health problems and ethnic groups. It is also unclear whether they could increase the risk of more serious infection.

More than 20 candidate vaccines are currently being tested on humans.