Source: How the Sinopharm Vaccine Works | The Herald
Jonathan Corum and Carl Zimme
In early 2020, the Beijing Institute of Biological Products created an inactivated coronavirus vaccine called BBIBP-CorV.
Clinical trials run by the state-owned company Sinopharm showed that it had an efficacy rate of 79 percent. China approved the vaccine, and soon began exporting it to other countries.
A Vaccine Made From Coronaviruses
BBIBP-CorV works by teaching the immune system to make antibodies against the SARS-CoV-2 coronavirus. The antibodies attach to viral proteins, such as the so-called spike proteins that stud its surface.
To create BBIBP-CorV, the Beijing Institute researchers obtained three variants of the coronavirus from patients in Chinese hospitals. They picked one of the variants because it was able to multiply quickly in monkey kidney cells grown in bioreactor tanks.
Killing the Virus
Once the researchers produced large stocks of the coronaviruses, they doused them with a chemical called beta-propiolactone. The compound disabled the coronaviruses by bonding to their genes. The inactivated coronaviruses could no longer replicate. But their proteins, including spike, remained intact.
The researchers then drew off the inactivated viruses and mixed them with a tiny amount of an aluminum-based compound called an adjuvant. Adjuvants stimulate the immune system to boost its response to a vaccine.
Inactivated viruses have been used for over a century. Jonas Salk used them to create his polio vaccine in the 1950s, and they’re the bases for vaccines against other diseases including rabies and hepatitis A.
Prompting an Immune Response
Because the coronaviruses in BBIBP-CorV are dead, they can be injected into the arm without causing Covid-19. Once inside the body, some of the inactivated viruses are swallowed up by a type of immune cell called an antigen-presenting cell.
The antigen-presenting cell tears the coronavirus apart and displays some of its fragments on its surface. A so-called helper T cell may detect the fragment. If the fragment fits into one of its surface proteins, the T cell becomes activated and can help recruit other immune cells to respond to the vaccine.
Making Antibodies
Another type of immune cell, called a B cell, may also encounter the inactivated coronavirus. B cells have surface proteins in a huge variety of shapes, and a few might have the right shape to latch onto the coronavirus. When a B cell locks on, it can pull part or all of the virus inside and present coronavirus fragments on its surface.
A helper T cell activated against the coronavirus can latch onto the same fragment. When that happens, the B cell gets activated, too. It proliferates and pours out antibodies that have the same shape as their surface proteins.
Stopping the Virus
Once vaccinated with BBIBP-CorV, the immune system can respond to an infection of live coronaviruses. B cells produce antibodies that stick to the invaders. Antibodies that target the spike protein can prevent the virus from entering cells. Other kinds of antibodies may block the virus by other means.
Remembering the Virus
Sinopharm’s clinical trials have demonstrated that BBIBP-CorV can protect people against Covid-19. But no one can yet say how long that protection lasts. It’s possible that the level of antibodies drops over the course of months. But the immune system also contains special cells called memory B cells that might retain information about the coronavirus for years or even decades.
Vaccine Timeline
January, 2020 Sinopharm begins developing an inactivated vaccine against the coronavirus.
June Researchers report the vaccine produces promising results in monkeys. A Phase 1/2 trial shows that the vaccine doesn’t cause any serious side effects and enables people to make antibodies against the coronavirus.
July A Phase 3 trial begins in the United Arab Emirates.
August Phase 3 trials begin in Morocco and Peru.
Sept. 14 The U.A.E. gives emergency approval for Sinopharm’s vaccine to use on health care workers. Government officials and others begin to receive it.
November The chairman of Sinopharm says almost a million people in China have received Sinopharm vaccines.
Nov. 3 The ruler of Dubai, Sheikh Mohammed bin Rashid al-Maktoum, announces he received the vaccine.
Dec. 9 The U.A.E. gives full approval to BBIBP-CorV, announcing it has an efficacy rate of 86 percent. But the government did not release any details with their announcement, leaving it unclear how they had come to their conclusions.
Dec. 13 Bahrain also approves the vaccine.
Dec. 30 Sinopharm announces that the vaccine has an efficacy of 79.34 percent, leading the Chinese government to approve it. The company has yet to publish detailed results of their Phase 3 trial.
Jan. 3, 2021 Egypt authorizes the vaccine for emergency use.- The New York Times
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