US health regulators could approve a third Covid-19 shot for adults beginning at least six months after full vaccination, instead of the previously announced eight-month gap, the Wall Street Journal reported on Wednesday.

Approval of boosters for three Covid-19 shots being administered in the United States — those manufactured by Pfizer Inc and partner BioNTech SE, Moderna Inc, and Johnson & Johnson — is expected in mid-September, the report said, citing a person familiar with the plans.

Pfizer and BioNTech have already...