Top US infectious disease expert Dr Anthony Fauci says an additional Covid-19 booster shot will be recommended for previously vaccinated people with weakened immune systems, Reuters quotes him as telling the NBC News during an interview.

He said that he expects the booster recommendation to come imminently.

The infectious expert says that "inevitably there will be a time when we will have to get boosts because no vaccine, at least not within this category, is going to have an indefinite amount of protection."

Fauci says for other vaccinated groups, such as the elderly, data is being collected to determine if or when their protection goes below a critical level and that’s when you’re going to be hearing about the implementation of boosters for others.