Resuming the use of Johnson & Johnson's Covid-19 vaccine in the United States will require clear guidelines for the medical community on how to best treat patients that develop a rare type of blood clot, as well as alerting vaccine recipients to be aware of the telltale symptoms, according to heart doctors and other medical experts.

US health regulators recommended last week that use of the J&J vaccine be paused after six cases of rare brain blood clots, accompanied by low platelet levels, were reported in women following vaccination.

"My estimate is that we will continue to use it in some form," Dr Anthony Fauci, chief medical adviser to President Joe Biden, said on Sunday on NBC's "Meet the Press". “I do think that there will likely be some sort of warning or restriction or risk assessment."

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