How Cold Viruses Are Being Used in COVID-19 Vaccine Candidates

Modified common cold viruses are being used to create COVID-19 vaccine¹ candidates in China and Russia. Such viruses have been studied for over 30 years, but are still not widely used. They are now driving the vaccine research from Russia's Gamaleya Institute and China's CanSino Biologics.

Adenovirus type 5 (Ad5)

The COVID-19 vaccine candidates are called adenovirus vector vaccines². They use modified adenovirus type 5, or Ad5, viruses. Unlike most viruses, modified viruses will not cause infection because they cannot reproduce on their own.

Ad5 viruses can be used as vectors to carry genes⁴ from the virus that causes COVID-19 into the body. The human cells will then create proteins to activate⁵ the body's natural defenses to guard against the virus.

Has Ad5 been successful in the past?

In the 1970s, Frank Graham of Canada was the first researcher to work with Ad5 viruses. At the time, he was working at a laboratory in The Netherlands.

Graham planned to use the viruses to study natural processes responsible for cancer. He also wanted to provide the human kidney cell line that makes them, called HEK293, to researchers all over the world.

"The cells became tremendously widespread and popular" among researchers, said Graham, who is now retired⁷ and lives in Italy.

In early gene³ therapy, Ad5 vectors were tested to replace a missing or damaged gene. Researchers stopped using them after an 18-year-old died in 1999 when the patient's natural defense⁶ system overreacted. The patient had received a large dose of Ad5 vectors during a gene therapy test. However, they believe much smaller doses would have been a good choice to use in developing a vaccine.

At McMaster University in Canada, Graham and other researchers developed several Ad5 vectors, including one for a rabies vaccine used on wild raccoons. They began developing an Ad5-based vaccine against Severe Acute Respiratory Syndrome⁸ (SARS) in 2003 and published early test results. The project was set aside when the SARS outbreak ended.

COVID-19 vaccine with Ad5 in China, Russia

In 2011, CanSino Biologics developed an experimental tuberculosis⁹ vaccine based on Ad5 from the McMaster researchers. The Chinese company then turned its attention to an Ad5-based Ebola vaccine at the request of the Chinese military. The Ebola vaccine was approved for military use in 2017.

In June of this year, the Chinese military approved emergency use of CanSino's COVID-19 vaccine without Phase 3 testing. Under Phase 3 trials, an experimental vaccine is tested on tens of thousands of volunteers to measure its effectiveness.

The Gamaleya Research Institute, which developed Russia's coronavirus vaccine, also used Ad5 vectors to develop an Ebola vaccine. The institute said that vaccine has been given to about 2,100 people.

For COVID-19, Russian researchers are combining Ad5 with another modified adenovirus called Ad26.

On August 11, Russian President Vladimir Putin announced that his country was the first to approve a vaccine for COVID-19. The approval came less than two months after the start of human testing of the vaccine. And the treatment has yet to complete Phase 3 trials.

Scientists around the world have questioned whether its quick approval without extensive testing will lead to a safe vaccine.

I'm Jonathan Evans.

Words in This Story

modify - v. to change some parts of something while not changing other parts

vector - n. a virus that carries germs that cause disease

therapy - n. the treatment

dose - n. the amount of medicine or drug taken at one time

outbreak - n. a sudden start or increase of disease

1 vaccine   

n.牛痘苗，疫苗；adj.牛痘的，疫苗的

参考例句：

• The polio vaccine has saved millions of lives.脊髓灰质炎疫苗挽救了数以百万计的生命。
• She takes a vaccine against influenza every fall.她每年秋季接种流感疫苗。

2 vaccines   

疫苗，痘苗( vaccine的名词复数 )

参考例句：

• His team are at the forefront of scientific research into vaccines. 他的小组处于疫苗科研的最前沿。
• The vaccines were kept cool in refrigerators. 疫苗放在冰箱中冷藏。

3 gene   

n.遗传因子，基因

参考例句：

• A single gene may have many effects.单一基因可能具有很多种效应。
• The targeting of gene therapy has been paid close attention.其中基因治疗的靶向性是值得密切关注的问题之一。

4 genes   

n.基因( gene的名词复数 )

参考例句：

• You have good genes from your parents, so you should live a long time. 你从父母那儿获得优良的基因，所以能够活得很长。 来自《简明英汉词典》
• Differences will help to reveal the functions of the genes. 它们间的差异将会帮助我们揭开基因多种功能。 来自英汉非文学 - 生命科学 - 生物技术的世纪

5 activate   

vt.使活动起来，使开始起作用

参考例句：

• We must activate the youth to study.我们要激励青年去学习。
• These push buttons can activate the elevator.这些按钮能启动电梯。

6 defense   

n.防御，保卫；[pl.]防务工事；辩护，答辩

参考例句：

• The accused has the right to defense.被告人有权获得辩护。
• The war has impacted the area with military and defense workers.战争使那个地区挤满了军队和防御工程人员。

7 retired   

adj.隐退的，退休的，退役的

参考例句：

• The old man retired to the country for rest.这位老人下乡休息去了。
• Many retired people take up gardening as a hobby.许多退休的人都以从事园艺为嗜好。

8 syndrome   

n.综合病症；并存特性

参考例句：

• The Institute says that an unidentified virus is to blame for the syndrome. 该研究所表示,引起这种综合症的是一种尚未确认的病毒。
• Results indicated that 11 fetuses had Down syndrome. 结果表明有11个胎儿患有唐氏综合征。

9 tuberculosis   

n.结核病，肺结核

参考例句：

• People used to go to special health spring to recover from tuberculosis.人们常去温泉疗养胜地治疗肺结核。
• Tuberculosis is a curable disease.肺结核是一种可治愈的病。