AstraZeneca defends coronavirus vaccine with new study

AstraZeneca and Oxford University on Monday said a new large-scale study had shown no safety concerns surrounding their COVID-19 vaccine.

The developers said the late-stage human trial study of more than 32,000 volunteers — across all age groups — revealed no safety concerns.

What did the vaccine developers say?

The UK-Swedish company said an independent safety committee had conducted a specific review of the blood clots based on the latest study.

The panel, with the help of an independent neurologist, also looked at cerebral venous sinus thrombosis (CVST), an extremely rare blood clot in the brain.

The trial involved 32,449 participants, with two-thirds actually receiving the jab rather than a placebo.

AstraZeneca said the panel found "no increased risk of thrombosis or events characterized by thrombosis among the 21,583 participants receiving at least one dose of the vaccine. The specific search for CVST found no events in this trial."

AstraZeneca said its vaccine was 79% effective at preventing symptomatic COVID-19 in the overall population.

It also said the vaccine was 100% effective at preventing severe disease and hospitalization.

Some 20% of the participants were 65 or older, and about 60% had health conditions associated with a higher risk, such as diabetes, severe obesity or heart disease.

"In many different countries and across age groups, the vaccine is providing a high level of protection against COVID-19 and we hope this will lead to even more widespread use of the vaccine in the global attempts to bring the pandemic to an end," said Oxford University Professor of Virology Sarah Gilbert. 

Those sentiments were echoed by Mene Pangalos, executive vice president of biopharmaceuticals research for AstraZeneca.

"We are confident this vaccine can play an important role in protecting millions of people worldwide against this lethal virus," said Pangalos.

What were the concerns?

The results come after numerous countries halted their use of the AstraZeneca jab.

More than a dozen countries, mostly in Europe, temporarily suspended the vaccine's use after reports it was linked to blood clots.

On Thursday, the European Medicines Agency (EMA) concluded that the vaccine did not raise the overall risk of blood clots. However, it could not rule out that the jab was connected to two very rare types of clots.

Many EU countries, including France, Germany and Italy have since resumed inoculations after the bloc's regulator said it was safe. However, the concerns about the vaccine appear to linger among many potential recipients.

Researchers at the Greifswald teaching hospital in northern Germany said last week that they had discovered the cause of the unusual blood clotting found in some recipients.

How does the vaccine work?

The vaccine shots are made with a harmless cold virus that normally infects chimpanzees and acts like a Trojan horse to carry the spike protein's genetic material into the body.

This in turn produces a harmless version of the spike protein, which primes the immune system to fight the real virus if it comes along.

Two other companies, Johnson & Johnson and China's CanSino Biologics, make COVID-19 vaccines that use the same idea but different cold viruses.

Confusion over early results

Scientists had been waiting for the results of the latest study in hope that it would clear up some of the confusion about the efficacy of the shot.

Britain first authorized the vaccine based on partial results from testing in the United Kingdom, Brazil and South Africa. These suggested the shots were only about 70% effective.

However, those results were clouded by a manufacturing error, meaning that some participants received only half a dose in their first shot. The mistake was not immediately acknowledged by the researchers.