Two COVID-19 Vaccines Are Entering Phase 2 Human Testing

There are currently two promising candidates that are providing us with encouraging early data while numerous vaccines are racing towards phase 2 human testing. The very first peer-reviewed and published data from a phase 1 human trial of a COVID-19 vaccine have been seen in a new article in The Lancet. The first of the two vaccines is known as Ad5-nCoV and it is undergoing development by CanSino Biologics – a Chinese drug-maker.

The phase 1 vaccine trials are aimed at ensuring safety in healthy human subjects. Efficacy is determined by examining how well the vaccine is capable of stimulating the body’s immune response – measured using the levels of T-cells and neutralizing antibodies. Wei Chen from the Beijing Institute of Biotechnology said, ‘The trial demonstrates that a single dose of the new adenovirus type 5 vectored COVID-19 (Ad5-nCoV) vaccine produces virus-specific antibodies and T cells in 14 days, making it a potential candidate for further investigation.’

However, there are some potential issues with this vaccine. Feng-Cai Zhu from Jiangsu Provincial Center for Disease Control and Prevention in China said, ‘Our study found that pre-existing Ad5 immunity could slow down the rapid immune responses to SARS-CoV-2 and also lower the peaking level of the responses. Moreover, high pre-existing Ad5 immunity may also have a negative impact on the persistence of the vaccine-elicited immune responses.’

Michael Mina from Harvard’s T.H. Chan School of Public Health said, ‘If you already have seen a virus or have some pre-existing immunity to it … you run the risk of having your immune response get skewed and picking up primarily the thing you’re already immune to or that you’ve already seen and not focusing so much on the new aspect, which in this case would be the coronavirus proteins that were placed onto the adenovirus vector.’

Another vaccine that is proving to be promising and is making progress towards advanced clinical trials is known as ChAdOx1 nCoV-19. It is undergoing development by scientists at Oxford University. The vaccine has already been administered to more than 1,000 subjects as a part of its first safety phase testing. Phase 2 of the trial will be using 10,000 subjects while increasing the demographics. No data has been published as of yet other than a pre-print study that claimed successful results from running initial animal studies.

Syringe. Disposable plastic medical syringe surrounded by sealed medication vials.

The head of the Oxford Vaccine Group, Andrew Pollard said, ‘The clinical studies are progressing very well and we are now initiating studies to evaluate how well the vaccine induces immune responses in older adults and to test whether it can provide protection in the wider population. We are very grateful to the huge support of the trial volunteers in helping test whether this new vaccine could protect humans against the pandemic coronavirus.’

There are about seven other vaccines that are in the early stages of human testing. We hope that these scientists can pull off a breakthrough as soon as possible.