Explainer: How does AstraZeneca’s vaccine compare with Pfizer-BioNTech?
Explainer-How does AstraZeneca’s vaccine compare with Pfizer-BioNTech?
ZURICH (Reuters) – Britain on Wednesday became the first country to approve AstraZeneca and Oxford University’s home-grown UK COVID-19 vaccine, 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 sceptical, 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 overall efficacy in preventing symptomatic infections was 70.4%, compared with the 95% efficacy of the shot from Pfizer/BioNTech, the other vaccine approved in Britain.
Single-dose efficacy was pegged at 52.7%, Britain said on Wednesday, in guidance to health workers, though a UK medical adviser also said that one AstraZeneca dose should be 70% effective after three weeks.
The UK regulator recommends a booster shot four to 12 weeks after the first dose, because up to 80% efficacy was reached with a three-month interval between shots, an official involved in the approval decision by the Medicines and Healthcare products Regulatory Agency (MHRA) said.
Confusion over efficacy emerged after interim late-stage trial results announced in late November when AstraZeneca acknowledged that people in its clinical trial accidentally got different doses.
A medical worker shows a dose of the Pfizer-BioNTech COVID-19 vaccine at the Regional Military Specialty Hospital in San Nicolas de los Garza, on the outskirts of Monterrey, Mexico December 29, 2020. REUTERS/Daniel Becerril
Those who received a half dose of the vaccine, followed by a full dose, were shown to have 90% protection, the company said initially, while two full doses offered only 62% 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.
FILE PHOTO: A small shopping basket filled with vials labeled “COVID-19 – Coronavirus Vaccine” and a medical sryinge are placed on a AstraZeneca logo in this illustration taken November 29, 2020. Picture taken November 29, 2020. REUTERS/Dado Ruvic/Ilustration
AstraZeneca pledged the vaccine would cost just a few dollars per dose and be sold without making a profit, whereas Pfizer’s vaccine costs $18.40-$19.50 per dose.
A separate mRNA vaccine from Moderna, approved in the United States, costs up to $37.
The AstraZeneca shot doesn’t require deep freezing at minus 70 degrees 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’s also cheaper to make, bringing hope to developing countries largely left out of the early vaccine haul.
NOW THAT THE UK HAS APPROVED THE VACCINE, WILL OTHER GOVERNMENTS FOLLOW?
When Britain signed off on Pfizer/BioNTech’s vaccine in early December, that pressured regulators elsewhere, and the United States and Europe followed in short order.
Moderna’s similar mRNA vaccine has also received U.S. approval.
