The US on Thursday authorised an extra dose of Covid vaccine for people with weakened immune systems, as the country struggles to thwart the Delta variant.
Emergency use authorisation for a third injection of the Pfizer-BioNTech and Moderna vaccines was granted by the US Food and Drug Administration (FDA) regulator.
“The country has entered yet another wave of the Covid-19 pandemic, and the FDA is especially cognisant that immunocompromised people are particularly at risk for severe disease,” said acting FDA commissioner Janet Woodcock in a statement.
“Other individuals who are fully vaccinated are adequately protected and do not need an additional dose of Covid-19 vaccine at this time,” she added.
The FDA said the additional dose was for solid organ transplant recipients or those with equivalent weakened immune systems.
US health authorities had been debating whether a third dose may be required, following a similar move by Israel.
More than 619,000 people have died in the US from Covid-19, with case numbers increasing sharply in recent months due to the spread of the Delta variant.
The country’s rapid vaccination programme has slowed particularly in politically conservative regions in the South and Midwest, and among younger people, those with lower income and racial minorities.