Senior health authorities in the US on Tuesday proposed a "pause" in using the Johnson & Johnson Covid-19 vaccine as they look into any links between the jab and severe blood clots.

The Food and Drug Administration (FDA) and the Centers for Disease Control (CDC) said the recommended halt in the jab’s administration was "out of an abundance of caution".

The two said they were are evaluating the "potential significance" of 6 reported cases of a rare blood clot in patients who had received the Johnson & Johnson shot, tweeted FDA.

"Until that process is complete, we are recommending this pause," FDA posted on Tuesday.

Johnson & Johnson vaccine. PHOTO/COURTESY

The American regulator revealed that more than 6.8 million doses of the particular vaccine had already been administered within the US as of Monday.

"CDC & FDA are reviewing data involving 6 reported U.S. cases of a rare & severe type of blood clot in individuals after receiving the vaccine. Right now, these adverse events appear to be extremely rare," FDA added.

The pause, it said, would allow medics to better prepare adequately to deal with such cases.

CDC said it will plan an advisory meeting on Wednesday to probe the blood clot cases and their potential significance as the country as given 120 million Coronavirus 19 jabs so far.

This comes as Johnson & Johnson said it will delay the rollout of its Covid-19 vaccine in Europe due to reports that 6 women in the US had developed blood clots after vaccination.