Ruminations: The Many Puzzling Outcomes of COVID

"It seems that the Oxford-AstraZeneca vaccine initially induces higher levels of T-cells than the mRNA vaccines."
"These T-cells are important for long-term immune memory and also for inhibiting virus replication and killing infected cells once an infection becomes established."
"Since the AZ vaccine is slightly better at inducing these T-cells, the implication is that it may provide longer-term protection against hospitalization and death."
"I think this is the point that Dr.Soriot was making."
Eleanor Riley, professor of immunology and infectious disease, University of Edinburgh

A woman receives her covid-19 vaccination booster jab, London, UK Leon Neal/Getty Images

The chief executive of AstraZeneca, Pascal Soriot on Tuesday responded to a puzzle that scientists are mulling over. That while the defences of Europe are crumbling against COVID-19 with steadily mounting infections and deaths related to the coronavirus, Britain in contrast is managing to keep its serious cases relatively low in both hospitalizations and resulting deaths. The explanation he offered was that the Oxford vaccine produces a more durable T-cell response, which could be what is ensuring that older people in Britain are safer than their continental counterparts in the prevention of hospitalization and death.

Cases remain high in Britain, the country is struggling just like other parts of Europe, with rising numbers but hospitalization and death appears under a firmer control than elsewhere. The AstraZeneca vaccine has been hugely unpopular in Europe, viewed with great suspicion. Leading to France, Germany, Spain and Belgium restricting its use to those under 65 in the early roll-out stage. Suspicion was aroused that there was insufficient data to ensure it was effective in older people.

Now, Dr.Soriot suggests that data demonstrate the AstraZeneca shot offers long-term protection, with a response that appears more durable than the mRNA vaccines produced by Pfizer and Moderna. The data of which he speaks is not yet published and has not as a result been reviewed by any outside sources for whom it would be of consuming interest. T-cells, without a shadow of a doubt, have an important role to play in protection against COVID. Antibodies wane over time, but T-cells remain able to trigger powerful immune responses, and to directly destroy infected cells, as well to work against new variants.

Closed Christmas stands in the city centre, Vienna, Austria. Lisa Leutner/AP/Shutterstock

The University of Birmingham in April found five weeks following a first dose people over 80 given AstraZeneca or Pfizer showed similar antibody responses. In the AstraZeneca group, double T-cell response was observed. Along with the strength of the T-cell response held to be three times higher than for the Pfizer group. Oxford University researchers found, in mid-June a still robust T-cell response from AstraZeneca doses at six months that even with a single dose; antibody immunity drops aside.

Scientists from Oxford and Switzerland in July concluded that long-term immunity could be greater for adenovirus vaccines like AstraZeneca resulting from "cellular training camps" for T-cells that they create. On the other hand, in the long term, mRNA vaccines also produce strong T-cell responses, perhaps more so than AstraZeneca, according to more recent research. A new paper published in Nature found Pfizer produced close to a six times greater number of T-cells than AstraZeneca, some 18 to 42 days following the second dose.

Data collected in real-world situations consistently indicate that the mRNA vaccines gain a slight improvement in prevention of infection and avoidance of serious disease than does AstraZeneca, an inconsistency with claims better protection is provided by the Oxford vaccine. Another interpretation of the situation could be that Britain has had so much recent infection that COVID is near to becoming an endemic virus. In the United Kingdom the booster program began earlier so that at present over 12 million adults now have had their third, 'booster' dose, which is recognized as having prevented tens of thousands of deaths.