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How the Pfizer vaccine is different from CanSino’s in Pakistan trials

CanSino’s final clinical trials to conclude in January

SAMAA | - Posted: Nov 16, 2020 | Last Updated: 1 year ago
Editing & Writing | Usman Shahid
Posted: Nov 16, 2020 | Last Updated: 1 year ago

Photo: AFP

US pharma Pfizer, with its German partner BioNTech, announced on November 9 “90% efficacy” of their COVID-19 vaccine. But results are awaited from China’s CanSino Biologics, whose vaccine is undergoing final clinical trials in Pakistan

Despite having different compositions, all COVID-19 vaccines under development have to trick our body into thinking there is a pathogen in order to produce antibodies to fight it. They will leave the body with “memory cells” called B-lymphocytes and T-lymphocytes. These are special immune cells that will remember how to fight the pathogen in future.

Clinical trials in Pakistan

In September, Pakistan started its first-ever clinical trials of the Chinese COVID-19 vaccine, Ad5-nCoV. Phase three clinical trials are expected to conclude by January, 2021.

Of 40,000 volunteers from China, Russia, Chile, Mexico, Saudia Arabia, Argentina, 8,000 to 10,000 will be from Pakistan, according to Federal Minister for Planning Asad Umer.

Initial results are expected in four to six months.

Primary trial sites in Pakistan include:

-Aga Khan University Hospital (Karachi)
-Indus Hospital (Karachi)
-Shaukat Khanum Memorial Hospital
-University of Health Sciences (Lahore)
-Shifa International Hospital (Islamabad)

Here’s a look at how the Chinese vaccine under study in Pakistan is different from Pfizer’s.

CanSinBio’s Ad5-nCoV

What it is

Adenovirus type-5 vectored vaccine is based on recombinant technology in which an adenovirus is made deficient.

It uses a weakened version of the virus, with a gene from the SARS-CoV-2 (novel coronavirus) engineered into it. Adenovirus, which is a common cold virus, is generally used in these vaccines.


Once injected, the adenoviral vector sends genetic material to the cells to produce “spike” proteins, proteins that help the coronavirus invade cells. This works like a natural pathogenic invasion and causes our immune system to trigger a response and produce antibodies.

Our body builds T-lymphocytes and B-lymphocytes that spring into action when the virus strikes in future.


There were 508 subjects in the Phase 2 Chinese trials. They were monitored for 30 minutes after being injected for any adverse effects.

Twenty-eight days later, either T-cells or antibody responses were found in 95% of subjects in the high dose group and 91% in the low dose group.

The vaccine has already been approved in China and its safety is ensured, according to National Institute of Health Executive Director Major General Aamer Ikram.

Side effects

No severe adverse effects have been observed so far, according to CanSino’s Chief Scientific Officer Zhu Tao.

Mild reactions included fever, fatigue and sore injection site.

Pfizer’s BNT162b2

What it is

BNT162b2 is developed using the RNA-based technology. It contains messenger-RNA, a molecule that carries instructions for cells to start producing “spike” proteins of the SARS-CoV-2. But spike proteins in mRNA vaccines are synthetic and cause no serious harm to the body.


An mRNA vaccine trains our immune system and instructs it to produce antibodies against the virus that causes COVID-19. The synthetic spike proteins trick our immune system into thinking that a virus is present in the body.

Upon recognising this threat, our immune system is stimulated and starts making antibodies in a defensive response to fight the virus.


Pfizer says their vaccine showed 90% ability to prevent COVID-19. Of 43,538 volunteers, 38,955 received their second dose in the third clinical trials.

Immune responses were observed in the participants just seven days after the second dose, and 28 days after the first.

The subjects included 42% global and 30% US participants of racially and ethnically diverse backgrounds.

Side effects

No serious safety concerns have been observed, according to Pfizer.

Mild reactions included headache, chills, fatigue, and muscle and joints pain.

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Pakistan coronavirus vaccine, Pakistan covid, Pfizer coronavirus vaccine, CanSino vaccine

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