Washington (AFP)

Two experimental vaccine trials against Covid-19 will be able to resume in the United States after apparent false alerts, increasing the chances of having one or more vaccines authorized by the start of 2021, in addition to two others American projects.

One, developed by the British University of Oxford and the AstraZeneca group, has already resumed in the United States, after more than six weeks of interruption in the country.

And the other, led by Johnson & Johnson, is expected to do so soon, after the green light from the independent committee that assessed the case of an unexplained illness that occurred in a participant in October.

A total of ten European, American, Chinese and Russian vaccines are being tested around the world in large-scale trials, including tens of thousands of participants each time, and intended to verify efficacy and, just as crucially, l safety.

The fear of regulators is that vaccines trigger serious side effects.

If a participant becomes ill, the trials can therefore be suspended until they understand whether the vaccine is involved.

For the experimental AstraZeneca / Oxford vaccine, the UK concluded after a few days that it was safe and cleared for resuming, followed in the following weeks by South Africa, Brazil and Japan.

In the United States, on the other hand, the authorities prolonged the suspense, without explanation.

Testing was suspended on September 6.

"The Medicines Agency (FDA) today authorized the resumption in the United States, following the resumption of trials in other countries in recent weeks," said AstraZeneca.

"The FDA has reviewed the safety data set from the global trials and concluded it is safe to resume trials."

The results of the trial are expected this year, the group confirmed, although it depends on the pace of the outbreak where the vaccine is being tested.

Many countries rely on this vaccine.

AstraZeneca has pre-sold hundreds of millions of doses on several continents, and signed partnerships with other producers to have the doses produced locally, the expected demand amounting to billions of doses.

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Johnson & Johnson announced on Friday that an independent committee had recommended the resumption of the Phase 3 trial, which will include 60,000 people and began in late September, and that preparations are underway.

"After a thorough assessment of a serious medical event in one participant, no definite cause was identified," the group said.

"The company found no evidence that the vaccine candidate caused the event."

The advantage of this vaccine is that it is only done in one dose, instead of two in most competitors, which saves three or four weeks for evaluation.

"If all goes well, we anticipate that the test could go quite quickly," said US official Paul Mango.

The Trump administration is increasingly confident that a vaccine will be available before the end of December, and logistics are being put in place for mass distribution.

The two leading candidates are those of Pfizer and Moderna: the American companies plan to apply for an authorization in the second half of November;

the FDA did not specify how soon it would then give its opinion, but that could happen well before the end of December.

"By the end of the year, we should be able to immunize our most vulnerable citizens," said Paul Mango.

"By the end of January, we think we will be able to vaccinate all seniors, and by March or April, all Americans who wish."

© 2020 AFP