How does AstraZeneca compare with Pfizer-BioNTech?

ZURICH — Britain became the first country to approve AstraZeneca and Oxford University’s home-grown U.K. COVID-19 vaccine last week, adding an easy-to-manage shot to the arsenal of a nation desperate for pandemic relief.

Even so, scientists — and regulators in Europe, following the Brexit divorce — are skeptical, given confusion over trial results earlier that left experts questioning the robustness of the data.

HOW DOES THE ASTRAZENECA SHOT’S EFFICACY STACK UP TO OTHERS’?

The AstraZeneca/Oxford vaccine’s efficacy in preventing symptomatic infections was 70.4 per cent, according to interim data, after 30 of 5,807 people who got the two-dose vaccine developed COVID-19, compared with 101 of 5,829 people who got a placebo.

That compares with the 95 per cent efficacy of the twoshot vaccine from Pfizer/ BioNTech, the other vaccine approved in Britain.

While efficacy with any dose after one dose was pegged at 52.7 per cent, the U.K.’s Medicines and Healthcare products Regulatory Agency (MHRA) regulator also said an “exploratory analysis” of trial participants who got one full dose showed efficacy of 73 per cent from 22 days after the first shot.

The U.K. regulator recommends a booster shot four to 12 weeks after the first dose, because up to 80 per cent efficacy was reached with a three-month interval between shots, an official involved in the MHRA approval said.

“The first dose efficacy gives an indication of protection for a short period between the two doses, the second dose strengthens the immune response and is expected to provide a more durable immune response,” the University of Oxford, AstraZeneca’s partner, said.

Confusion over efficacy emerged after interim latestage trial results announced in late November when AstraZeneca acknowledged that people in its clinical trial accidentally got different doses.

Those who received a half dose of the vaccine, followed by a full dose, were shown to have 90 per cent protection, the company said initially, while two full doses offered only 62 per cent protection.

Now, however, the MHRA said the half-dose regimen’s results were not borne out in analysis.

“It’s all much more confusing because mistakes have been made, genuinely,” one European Medicines Agency (EMA) official told Reuters. “Mistakes that resulted in clinical data that was much more complex to interpret than Moderna’s and Pfizer’s. And on top of that the efficacy is lower.”

WHAT ARE THE OTHER DIFFERENCES?

Technology, price and storage.

The AstraZeneca shot is a “viral vector vaccine,” where a specially engineered virus that normally causes chimpanzees to get the common cold delivers genetic instructions to human cells to make the spike protein jutting out from the new coronavirus’s surface.

The Pfizer/BioNTech and Moderna vaccines use a new technology which packs messenger RNA (mRNA) inside tiny fat droplets to instruct cells to make the spike protein.

AstraZeneca pledged the vaccine would cost just a few dollars per dose and be sold without making a profit, whereas Pfizer’s vaccine costs US$18.40-$19.50 per dose.

A separate mRNA vaccine from Moderna, approved in the United States, costs up to US$37.

The AstraZeneca shot does not require deep freezing at -70 C like the mRNA vaccine from Pfizer and its German partner, BioNTech, and has already been produced by the millions of doses.

It can be kept in a standard refrigerator for six months.

It is also cheaper to make, bringing hope to developing countries largely left out of the early vaccine haul.