SHANGHAI — Doubts have arisen around the efficacy of China's Sinopharm vaccine after Bahrain began recommending over-50s with comorbidities get a booster of Pfizer-BioNTech six months after their second Sinopharm shot, the Wall Street Journal reports.
The Sinopharm vaccine works by teaching our immune systems how to attack the coronavirus using inactivated viruses which can't replicate, according to the New York Times.
Once injected into a patient, inactivated virus particles are swallowed by antigen-presenting cells that break them up and present fragments of them on their surfaces.
From there, helper T cells can attach to the fragments and send signals to activate other parts of the immune system, including B cells and cytotoxic T cells, according to Encyclopaedia Britannica.
Cytotoxic T cells attach to infected cells and subsequently program them to die, according to the journal Immunobiology.
B cells create antibodies that attach to viruses to prevent them invading cells, according to the New York Times.
The idea behind the Sinopharm vaccine is that the body's immune system remembers this response using memory B cells.
It is then ready to help reproduce the same specific antibodies if it comes into contact with a functioning coronavirus, according to the New York Times.
The Washington Post reports Bahrain may have been prompted to recommend Pfizer-BioNTech booster shots after the country saw its worst wave of cases since the pandemic began in recent weeks.
This came despite having vaccinated almost half of its population, mostly with the Sinopharm vaccine.
Bahrain's undersecretary of health, however, pointed out to the Wall Street Journal that despite the recommendation, more than 90 percent of people hospitalized in his country's current COVID-19 wave had not been vaccinated, and insisted that Sinopharm offered a high degree of protection.