A World Health Organization (WHO) advisory group on Thursday recommended that this year's Covid-19 booster shots be updated to target one of the currently dominant XBB variants.

The advisory group said that new formulations should aim to produce antibody responses to the XBB.1.5 or XBB.1.16 variants.

It adds that other formulations or platforms that neutralise antibody responses against XBB lineages could also be considered.

The group suggested no longer including the original Covid-19 strain be included in future vaccines, based on data that the original virus no longer circulates in human beings.

As such, shots targeting the original strain produce "undetectable or very low levels of neutralising antibodies" against currently circulating variants.

Covid-19 vaccine makers like Pfizer/BioNtech, Moderna Inc and Novavax Inc are already developing versions of their respective vaccines targeting XBB.1.5 and other currently circulating strains.

The US Food and Drug Administration is also set to hold a meeting of outside experts in June to discuss the strain compositions of Covid-19 shots for later this year.

Vaccine manufacturers must also update their shots once the strains are selected.

The bivalent booster shots developed and distributed last year targeted two different strains - the Omicron variant and the original virus.

WHO's advisory group, which recommends if changes are needed to the composition of future Covid-19 shots, said approved vaccines should continue to be used by the agency's recommendations.

In late March, WHO revised its Covid vaccination recommendations and suggested that healthy children and adolescents might not necessarily need a shot.

However, older and high-risk groups should get a booster between six and 12 months after their last vaccine.

The latest recommendations come about two weeks after WHO ended the global emergency status for Covid-19.

- Reuters