New York, Jan 29 (IANS): Several scientists have claimed that a Covid variant-specific vaccine is not needed, and that the existing shots are well effective against all variants, including Omicron.

However, global vaccine makers have raced ahead to develop shots against the highly-mutated and transmissible Omicron variant.

This week, both pharmaceutical firm Pfizer and biotechnology company Moderna announced that they have initiated clinical trials in which they are dosing people with Omicron-based vaccines.

But according to public-health authorities and infectious-disease specialists, whether rolling out these jabs is necessary, or even practical, is unclear, Nature reported.

According to some, an Omicron-specific jab may not be worthwhile because cases could plummet before the manufacturers could finalise the vaccines.

Others point out that it's difficult to predict whether the next SARS-CoV-2 variant will be like Omicron, calling into question the utility of an Omicron-specific shot.

"We have a lot of confidence in the [current] vaccines, but we must now discuss whether to update the composition," Kanta Subbarao, who chairs the Technical Advisory Group on Covid-19 Vaccine Composition for the World Health Organization (WHO), was quoted as saying.

Even if Pfizer is able to meet its ambitious goal -- just months from strain identification to clinical trial results -- it might still be too late to be useful, added Paul Bieniasz, a virologist at Rockefeller University in New York City.

Omicron's dominance as a variant could be waning by then, Subbarao said.

Such a vaccine might work against the variant that dominates after Omicron -- especially if the virus continues on that genetic trajectory. But no one knows how the virus will evolve, Bieniasz noted.

Covid vaccine boosters are also proving useful against Omicron, but scientists say that endless boosting might not be a practical or sustainable strategy.

Meanwhile, several scientists, including from the US National Institute of Allergy and Infectious Diseases (NIAID) and the global Coalition for Epidemic Preparedness Innovations (CEPI), are funding research for developing a pan-coronavirus vaccine, the report said.

A pan-coronavirus vaccine can broadly protect against many strains of SARS-CoV-2 and other types of coronavirus.

The World Health Organization is also working to devise a central system to update Covid vaccines, much like the current process used for flu jabs.

The strategy emulates a system currently used to decide on "strain updates" for flu shots, which are updated every six months, The Telegraph reported.