Singapore, Dec 2 The new Covid variant Omicron will likely "overwhelm the whole world" in the coming months, warned a Singapore-based infectious disease doctor.

According to Dr. Leong Hoe Nam of Mount Elizabeth Novena Hospital, vaccines against the strain can be developed quickly, but they need to be tested over three to six months to prove that they can provide immunity against the variant, CNBC reported.

"But frankly, omicron will dominate and overwhelm the whole world in three to six months," he was quoted as saying on CNBC's "Street Signs Asia".

All major drug makers including Pfizer, Moderna, Johnson and Johnson, and AstraZeneca have said that they are working to quickly investigate and adapt their shots to a new and highly mutated strain of the virus.

Moderna CEO Stephane Bancel on Monday said it will take months to develop and ship a vaccine that specifically targets the Omicron variant, and Pfizer CEO Albert Bourla added that shots could be ready in less than 100 days, or slightly over three months.

"Nice idea, but honestly, it is not practical," Leong said of a vaccine that specifically targets Omicron.

"We won't be able to rush out the vaccines in time and by the time the vaccines come, practically everyone will be infected with Omicron given this high infectiousness and transmissibility," he added.

Experts don't know exactly how contagious the highly mutated omicron variant is, but the virus' spike protein -- which binds to human cells -- has mutations associated with higher transmission and a decrease in antibody protection.

"The profile of the mutations strongly suggest that it's going to have an advantage in transmissibility and that it might evade immune protection that you would get," US infectious disease expert Dr Anthony Fauci was quoted as saying to NBC.

Leong agreed that a three-dose vaccine regimen would likely protect against severe disease, but pointed out that many countries still have low vaccination rates.

He said Omicron is "threatening the whole world" with a sudden surge in cases, and health-care systems could be overwhelmed, even if only 1-2 per cent of the cases end up in hospital".

Omicron was first detected in South Africa and was designated a variant of concern by the WHO last week. It has since been reported in 23 nations.

For now, however, Leong said we should continue to roll out vaccinations, keep our distance, wear masks, and not be overly concerned.

Omicron may dominate, overwhelm world in 3-6 months: Singapore Doc