Over the past several months, AstraZeneca has struggled to win broad support for its vaccine, which it jointly developed with Oxford University. In the past several months, a series of bruising headlines have put the company on the defensive, forcing the company to issue a series of statements answering questions over its vaccine data.
The AstraZeneca vaccine will likely be the fourth to be authorized in the U.S. There is “a growing body of evidence that shows this vaccine is well tolerated and highly effective against all severities of COVID-19 and across all age groups,” said Mene Pangalos, executive vice president, biopharmaceuticals R&D at AstraZeneca in a statement on data from its U.S. clinical trial.
Several health authorities ranging from the WHO to the U.K.-based Medicines and Healthcare products Agency have supported the vaccine’s safety and efficacy.
AstraZeneca did not immediately respond to a request for comment for this story.
November 2020: A mistake in dosing prompts questions
The company admitted it had made a dosing error when administering the first vaccine dose to some clinical trial recipients. That mistake, however, was fortuitous as it seemed to optimize the vaccine’s efficacy.
The news that the vaccine appeared to be 90% effective in recipients who received a half dose for the first vaccine shot would put it on a similar footing to the vaccines from rivals Pfizer and Moderna. But one dosing regimen led to a trial efficacy rate of 62%, and the average efficacy was 70%.
The varied results and other irregularities led some experts to question the early trial results. “I think that they have really damaged confidence in their whole development program,” Geoffrey Porges, an SVB Leerink analyst, told The New York Times.
However, the independent Data Safety Monitoring Board concluded based on the trial results from Brazil and the U.K. that the vaccine appeared to meet its primary endpoint of demonstrating protection from COVID-19 14 days after the second dose.
February 2021: South Africa suspends AstraZeneca vaccine use
South Africa decided not to use the AstraZeneca COVID-19 vaccine after a small study showed it was only about 10% in protecting against a variant circulating there. NEJM recently published more details from that study.
February 2021: Several EU countries question vaccine efficacy in people over 65
Also in February, several European countries decided to recommend that older adults avoid AstraZeneca’s vaccine, citing the need for more clinical trial data involving adults over 65. The prime minister of France, Emmanuel Macron, even stated that the vaccine was “quasi-ineffective” for people over 65 before changing his mind and endorsing its use for older adults. He later said he would gladly accept the vaccine if it were offered to him.
The E.U. nations’ worries related to a lack of data. Only two patients over 65 in the AstraZeneca trial developed symptomatic COVID-19, making it difficult to reach firm conclusions about its performance in older adults.
As more data became available, E.U. countries such as France and Germany authorized its use for people over 65.
A number of healthcare workers in Europe resisted the AstraZeneca vaccine over reports that it led to significant side effects. Authorities in France recommended staggering doses of the vaccine, and two regions in Sweden paused the use of the vaccine. In Germany, some essential workers have refused the vaccine, according to Reuters.
The company has stressed that there have been no confirmed serious adverse events linked to the vaccine.
March 2021: E.U. countries suspend use of AstraZeneca over blood-clot worries
Several countries in Europe and elsewhere suspended the use of the AstraZeneca COVID-19 vaccine over fears that it could cause blood-clotting problems in isolated cases. The company issued a statement concluding that it found “no evidence of an increased risk of pulmonary embolism, deep vein thrombosis (DVT) or thrombocytopenia, in any defined age group, gender, batch or in any particular country.”
Following that news, two separate research groups in Germany and Norway concluded that the AstraZeneca vaccine could cause an autoimmune reaction, which in turn causes thrombosis in a small number of patients. The findings have not yet been peer-reviewed.
In separate news, members of the data and safety monitoring board overseeing the AstraZeneca trial reached out to the federal government with concerns about data the company recently announced about the AZD1222 vaccine.
The news prompted AstraZeneca to confirm that the data were “based on a pre-specified interim analysis with a data cut-off of 17 February,” adding that it plans to release results from the primary analysis within 48 hours.