How does AstraZeneca’s vaccine compare to Pfizer-BioNTech?

ZURICH – Britain on Wednesday became the first country to approve the UK’s own-produced COVID-19 vaccine from the University of Oxford and AstraZeneca, adding an easy-to-administer injection to the arsenal of a nation desperate for relief from the pandemic.

Still, scientists – and regulators in Europe, following the Brexit divorce – are skeptical, given the confusion over the results of previous trials that left experts questioning the robustness of the data.

How does the effectiveness of AstraZeneca injection compare to others?

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

That compares with the 95% efficacy of the two-shot vaccine from Pfizer / BioNTech, the other vaccine approved in Britain.

While efficacy at any dose after a dose was set at 52.7%, the UK’s Medicines and Healthcare Products Regulatory Agency (MHRA) regulator also said that an “exploratory analysis” of trial participants found received a full dose showed an efficacy of 73% from 22 days after the first shot.

The UK regulator recommends a booster injection four to 12 weeks after the first dose, because efficacy of up to 80% was achieved with a three-month interval between injections, said an official involved in the approval of the MHRA.

“The efficacy of the first dose 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,” said AstraZeneca partner Oxford University.

Confusion about efficacy arose after interim results from the late-stage trial were announced in late November, when AstraZeneca acknowledged that people in its clinical trial accidentally received different doses.

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 results of the half-dose regimen were not confirmed in the analysis.

“Everything is much more confusing because mistakes have been made, really,” an official from the European Medicines Agency (EMA) told Reuters. “Errors that resulted in clinical data much more complex to interpret than Moderna and Pfizer. And besides that, the efficiency is lower. “

What are the other differences?

Technology, price and storage.

The AstraZeneca injection is a “viral vector vaccine,” in which a specially engineered virus that normally causes chimpanzees to contract the common cold sends genetic instructions to human cells to produce the spike protein that protrudes from the surface of the new one. coronavirus.

The Pfizer / BioNTech and Moderna vaccines use a new technology that packages messenger RNA (mRNA) into tiny droplets of fat to instruct cells to produce spike protein.

AstraZeneca promised that the vaccine would cost only a few dollars per dose and would sell without making a profit, while Pfizer’s vaccine costs between $ 18.40 and $ 19.50 per dose.

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

The AstraZeneca injection does not require deep freezing to minus 70 degrees like the mRNA vaccine from Pfizer and its German partner, BioNTech, and has already been produced by millions of doses.

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

It is also cheaper to manufacture, giving hope to developing countries that were largely left out of the first vaccination campaigns.

Now that the UK has approved the vaccine, will other governments follow?

When Britain approved the Pfizer / BioNTech vaccine in early December, that put pressure on regulators elsewhere, and the United States and Europe followed in no time.

Moderna’s similar mRNA vaccine has also received US approval.

Britain’s movement now to support AstraZeneca injection prioritizes getting as many people vaccinated quickly, before all the answers on efficacy and optimal dosage are available.

With no safety concerns, British regulators may be making a compromise between expecting perfection and making do with what they have.

“Rapid emergency approval means taking risks of less (or) shorter efficacy than can be achieved with mRNA vaccines,” said Claire-Anne Siegrist, director of vaccines and immunology at Geneva University Hospitals.

While an EMA official said this week that the injection is unlikely to be approved before the end of January, a senior German vaccine official said on Wednesday that he was still waiting for a “swift decision” from Europe, as his ongoing review is well under way.

The EU drug watchdog is conducting a review for conditional market approval, rather than the UK’s faster emergency use approval.

India’s drug regulator is also discussing the emergency approval of the AstraZeneca vaccine, which is being done in partnership with the Serum Institute of India.

Who will get what vaccine?

The National Health Service in England will not give people a choice of vaccinations.

But with several now available, countries must decide who should receive which vaccine, as some people may prefer injections more effectively.

The experts said the differences between the efficacy rates are significant, leading to difficult decisions.

“In countries where mRNA and AstraZeneca vaccines would be available, who do you decide to give the least effective vaccine to?” Siegrist said.

Thomas Mertens, director of STIKO, Germany’s panel of experts on the use of vaccines, told Reuters his group plans to tackle this problem “in the near future” as it hopes to devise a strategy that will have the greatest impact with limited supplies. .

However, some experts said that the election may be a luxury that countries cannot afford.

“Right now, we don’t have vaccines in sufficient quantities to reach all those who need them,” said Thomas Klimkait, a professor and researcher at the University of Basel who is working on a Swiss project for a vaccine against SARS-CoV-2.

“I would say at this point that all vaccines with a relatively good efficacy, that is, at least 60 or 70%, should be put to use, when they have an adequate safety profile.”

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