Any adverse effects from Covid-19 vaccines are for national authorities to review, the World Health Organization  (WHO) said on Friday in response to questions about Britain warning people with a history of anaphylaxis to avoid the Pfizer-BioNTech shot. "But people should not be too anxious. Remember there are a number of vaccine candidates coming online at the same time," WHO spokeswoman Margaret Harris told a UN briefing in Geneva. "One vaccine may not be suitable for particular individuals, but you may well find another vaccine is."

On Tuesday, Britain became the first country to roll out the Pfizer-BioNTech shot. Its medicine regulator subsequently said anyone with a history of anaphylaxis to a medicine or food should not get the shot, after two reported incidents of the reaction.

A panel of outside advisers to the US Food and Drug Administration on Thursday voted overwhelmingly to endorse the emergency use of the vaccine, paving the way for the agency to authorize the shot for a nation that has lost more than 285,000 lives to Covid-19.

The WHO is reviewing data from phase 3 trials of many Covid-19 vaccine candidates, Harris said. The agency has not yet issued emergency use authorization for any vaccines, but "the primary thing we look at is safety", she added.

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