Washington, Sep 25 : The US Centers for Disease Control and Prevention (CDC) Director Rochelle Walensky, in an unusual decision overruled her agency's recommendation and endorsed Covid booster shots for people who work in healthcare, schools and other settings where they are at higher risk of exposure to the Covid-19 virus.

"This was a scientific close call," said Walensky, defending her decision, during a press briefing of the White House coronavirus task force on Friday.

"I want to be very clear that I did not overrule an advisory committee," she added.

Walensky's recommendation, however, deviated from the advice of the CDC's Advisory Committee for Immunization Practices (ACIP), who in a four-part vote, unanimously voted to give Pfizer-BioNTech's Covid-19 shot to people aged 65 and older and long-term care facility residents. They recommended the additional jabs for Americans aged between 50 and 64 with underlying medical conditions by a vote of 13-2.

A third Covid dose was also recommended for people between ages 18 and 49 with pre-existing conditions, by a vote of 9-6.

However, the committee voted against recommended use for those at risk due to an 'occupational or institutional settings', the Daily Mail reported.

According to the members, there wasn't enough data to suggest that those who live in institutional settings that increase their risk of exposure, such as prisons or homeless shelters, as well as healthcare workers, teachers and grocery store employees, are at heightened risk.

"In that situation, it was my call to make. ...if I had been in the room, I would have voted ayes'," Wallensky said.

"As CDC Director, it's my job to recognise where our actions can have the greatest impact. In a pandemic, we most often take steps with the intention to do the greatest good even in an uncertain environment, and that is what I'm doing with these recommendations," she added.

In August, the US had approved boosters shots for immunocompromised Americans who received either the Pfizer or Moderna vaccine based on data that they were less likely to develop high antibody levels after two doses.

But many scientists, including senior officials at the FDA, disagreed with booster shots due to lack of data on the potential side effects, especially for younger adults who may be at risk for heart inflammation.

"Overall, data indicate that currently US-licensed or authorised Covid-19 vaccines still afford protection against severe Covid-19 disease and death in the United States,' the FDA scientists wrote in a briefing document last week.

Scientific call: CDC chief overrules panel endorses Covid boosters for front-line workers