US may approve Astrazeneca vaccine amid concerns over blood clot risks

• Independent monitors are analysing data from the 32,000-person US study to determine whether the vaccine is safe and effective.
• Independent monitoring boards periodically review data during clinical trials to make sure no safety problems crop up.
• AstraZeneca vaccine has been authorised for use in EU and many countries based on separate trial data.

CHICAGO:  A top US health official has stated that the US may approve the use of AstraZeneca Plc's coronavirus vaccine for emergency use in April after the trial is reviewed by independent monitors.

The independent monitors are analysing data from the 32,000-person US study to determine whether the vaccine is safe and effective. If the results are positive and all goes well, the US Food and Drug Administration would review the data and issue the authorization, Dr Francis Collins, director of the National Institutes of Health (NIH), said in an interview.

Collins estimates that the FDA would need about three weeks to analyse the trial data, after which an expert advisory panel will meet and vote on whether to recommend authorisation.

Read more: AstraZeneca issues statement after concerns raised over blood clot risks from COVID-19 vaccine

"We expect data from our US Phase III trial to be available soon, and we plan to file for emergency use authorisation shortly thereafter," AstraZeneca spokeswoman Michele Meixell said in a statement.

Independent monitoring boards periodically review data during clinical trials to make sure no safety problems crop up, and can halt studies early if it determines a drug or vaccine is likely to fail or is clearly going to be a success.

The AstraZeneca vaccine, developed with the University of Oxford, has been authorised for use in the European Union and many countries based on separate trial data. US regulators have been waiting for the US data.

Several EU countries have halted administering the AstraZeneca vaccine after reports from Denmark and Norway of possible serious side effects, including bleeding and blood clots.

Read more: WHO calls AstraZeneca coronavirus vaccine safe as countries suspend rollout

Asked about those issues, Collins said he has not personally seen the data but has been "pretty reassured" by statements from European regulators that the problems could be occurring by chance, and are not related to the vaccine.

With so many people being vaccinated, Collins said, some are bound to experience a blood clot around the same time they receive a vaccine.

"It's not clear at all" that people who receive the vaccine get blood clots at an increased rate, Collins said, adding "there may be a bit of an overreaction to something that is unrelated to the vaccine itself."

A World Health Organisation expert said on Monday he sees no association between reports of blood clots and the AstraZeneca vaccine and urged people not to panic.

Read more: WHO greenlights Johnson & Johnson's coronavirus vaccine

Asked about the emergence of more contagious viral variants that could evade vaccine protection, Collins said studies so far suggest that currently authorised vaccines from Pfizer Inc , Moderna Inc and Johnson & Johnson will be protective.

"We do not feel that we are in a difficult situation that requires immediate action in the US, but we've got to watch this really closely," said Collins, a geneticist who has led the NIH since 2009.

COVID-19 vaccine makers have already started work on booster doses of their shots that specifically target a concerning variant first discovered in South Africa. Those would be ready by the end of 2021 or early 2022.

It will not be clear until this summer or fall whether a booster dose is necessary, Collins said.

"I really hope that doesn't happen, but I think we would be foolish not to plan for that just in case, and so planning is happening," he said.