The CDC is investigating a "handful" of potential additional cases of severe side effects involving the Johnson & Johnson COVID-19 vaccine, the agency’s chief said Monday.

Use of the single-dose COVID-19 vaccine was halted in the US last week amid reports that six women in the country developed dangerous blood clots — including one who died — after receiving the immunization.

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CDC chief Dr. Rochelle Walensky — asked at a White House press briefing if there were any more reports of "severe adverse effects" involving J&J doses in the US — replied, "There have been a handful of cases — not an overwhelming number of cases.

"We’re going through and adjudicating them and verifying whether they do in fact reflect a true case," she said.

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Nearly 7 million Americans received the vaccine before the federal government urged that its use be halted, at least temporarily, until the CDC and FDA can further investigate.

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