A news report by Science and Technology Daily:

Good news. On July 20th, The Lancet published two papers online at the same 
time, revealing the results of clinical trials for two COVID-19 vaccines. From 
China and the United Kingdom respectively, the two stars on the track of 
adenovirus vector vaccine display a one-on-one competition.

What are the similarities and differences between the two vaccines in terms of 
clinical trial design and results despite that they have taken the same R&D 
approach? What are the characteristics of Chinese vaccines' R&D? How to 
perceive the potential of Oxford's vaccine?

Two-dose Protection or Single-dose immunity, which is more effective?

Led by Chen Wei, academician at China Academy of Engineering and researcher at 
Academy of Military Medical Sciences, Ad5-nCoV is the first COVID-19 vaccine 
around the globe to enter Phase II clinical trial. The most important feature 
of the trial is that eligible participants over 60 years old are involved, 
consisting 13% of the 508 total participants.

CanSino Biologics Inc. (CanSinoBIO) is in partnership with Chen's team 
regarding vaccine development. The president of CanSinoBIO, Yu Xuefeng, 
received interview by Science and Technology Daily. He noted, "From the 
perspective of trial design, the two trials share the same mechanism, namely 
inducing balanced humoral and cellular immune responses. There are also 
differences. We hope that a single-dose can be effective in the time of 
pandemic whereas the Oxford team further testes a "two-dose" protection."

According to news from Oxford website, Professor Andrew Pollard, head of the 
Oxford Vaccine Group, said: "We saw the strongest immune response in the 10 
participants who received two doses of the vaccine, indicating that this might 
be a good strategy for vaccination." 

Yu held a different view. He thought that the "fastest would be a single-dose 
injection" under the trend of the pandemic. The result of Chinese Vaccine's 
Phase II clinical trial showed that 95% of the participants in the high-dose 
group and 91% in the low-dose group showed either cellular or humoral immune 
responses at day 28 after vaccination.

"This means that single-dose vaccine not only takes effect quickly, but also 
has potential to be  effective of vaccination." 

One thing to note is that the elderly participants have a higher tolerability 
for the vaccine whereas they also display a lower level of immune response.

Chen's idea is widely quoted by the media. Once infected by the virus, the 
elderly is faced with high risks of severe diseases or even death. Therefore, 
they are an important target population for the COVID-19 vaccine.

Yu pointed out that with an additional dose, the immune response will be 
effectively intensified. The effect of two-dose vaccination was demonstrated  
in the clinical trial for the Ebola vaccine developed by CanSinoBIO with the 
same technology. For clinical trials in the future, how to achieve better 
protection for the elderly can be explored.

Chimpanzees or human being, which vector is safer?

Except for their efficacy, what about the safety of the two vaccines?

The AZD1222 vaccine by Oxford and AstraZeneca combines a weakened version of a 
common cold virus (adenovirus) that causes infections in chimpanzees and the 
genetic material of the SARS-CoV-2 virus. 

According to Yu, Ad5-nCoV uses adenovirus type 5 as vector, a weakened version 
of common adenovirus that can result in the infection of human beings rather 
than chimpanzees. "Although some participants may have 'existing immunity' due 
to their infection of adenovirus type 5 and impact the immune response, 
Ad5-nCoV ensures safety to the greatest extent from the source of the 
adenovirus vector."

Currently, the two vaccines are almost equally safe in terms of "safety 
evaluation" observed by public information from the media. Andrew Pollard and 
colleagues report their phase 1/2 randomized trial of one injection of 
chimpanzee adenovirus-vectored COVID-19 vaccine. Local and systemic adverse 
events such as fatigue, headache, and local tenderness occurred commonly in 
COVID-19 vaccines, but were tolerable and mostly ameliorated by paracetamol. No 
serious adverse events occurred. 

Chen and colleagues reported results from a phase 2 randomized trial of 
single-dose immunization schedule of Ad5-vectored COVID-19 vaccine. Most 
injection site and systemic solicited reactions from the participants in China 
were mild or moderate. Adverse reactions occurred in this study includes fever, 
fatigue, headache, and injection site pain.

According to the comment article written by Professor Naor Bar-Zeev and 
Professor William J Moss, "Overall, the results of both trials are broadly 
similar and promising, notwithstanding differences in the vector, in the 
geographical locations of the populations studied, and the neutralization 
assays used. These COVID-19 vaccine trials are small so inferential caution is 
warranted, but the explorations are laudable. Ethnic diversity in both these 
trials was very limited."

"Equal Global Access to COVID-19 Vaccine": China and UK's Common Goal and 
Commitment

"It is good news," Dr. Mike Ryan, executive director of the WHO's emergencies 
program, said at a press conference at the organization's Geneva headquarters 
shortly after the data was published in The Lancet. "In generating T-cell 
responses and generating neutralizing antibodies, this is a positive result. 
But again, there is a long way to go. We now need to move into larger-scale 
real-world trials."

He noted that once one of the vaccines is proven effective, the next challenge 
will be ensuring that there are enough doses to distribute globally.

"CanSinoBIO has always been in a strategic partnership with Academician Chen's 
research team and the Oxford University research team respectively. However, 
CanSinoBIO chose to cooperate with Chen's research team in the early stage of 
COVID-19 vaccine development," Yu said. "But it is undeniable that the 
cooperation between the Oxford team and AstraZeneca has potential advantages in 
the recruitment of volunteers for the Phase III clinical trial."

Although the vaccine developed by Oxford team still lags behind CanSinoBIO 
regarding the level of adenovirus vaccine production line, its developing 
progress is expected to be "accelerated" with the aid of huge funding and the 
support of the global vaccine distribution network, and eventually achieve 
large-scale production after the results of its Phase III clinical trial are 
revealed.

Author: Fang Linlin  Translated by Long Yun & Lu Zijian

SOURCE: Science and Technology Daily