Almost a month ago, President Joe Biden announced a plan to make coronavirus booster shots available to most adults in the United States eight months after they received their second dose.

US booster policy is in flux as studies add to dissent

The United States has authorised an extra dose of Covid vaccine for people with weakened immune systems, as the country struggles to thwart the Delta variant. "The country has entered yet another wave of the Covid-19 pandemic, and the FDA is especially cognizant that immunocompromised people are particularly at risk for severe disease," said acting Food and Drug Administration Commissioner Janet Woodcock in a statement.

US authorises Covid booster jabs for those with weak immune systems to thwart Delta variant

Calling for a halt on COVID-19 vaccine boosters until at least the end of September, WHO chief Tedros Adhanom Ghebreyesus has said that ''we cannot accept countries that have already used most of the global supply of vaccines using even more of it.

Halt the boosters: WHO says it is 'unacceptable' that some countries are using most of vaccine's global supply