Washington, Dec 16 (IANS): Existing vaccines and booster shots against Covid are sufficient to prevent Omicron infections, said top infectious disease expert Dr Anthony Fauci, as he advised against changing the vaccines to fight the new, highly contagious strain of the virus at this time.

It has been known that Omicron evades efficacy from the current two-dose shots. A study from South Africa showed that protection from the two-dose vaccine against infection dropped to 33 per cent compared with 80 per cent before the emergence of Omicron.

However, two doses are still 70 per cent effective at preventing hospitalisation in Omicron patients in South Africa, Fauci told the public during a White House Covid update on Wednesday, the CNBC reported.

"Our booster vaccine regimens work against Omicron. At this point, there is no need for a variant-specific booster.

"Obviously, this is significantly down but there is the maintaining of a degree of protection against hospitalisation," Fauci said.

As a result, a booster dose has been advised by several countries. A booster dose increases protection against symptomatic disease to 75 per cent, Fauci said, citing data from the UK Health Security Agency, the report said.

"And so the message remains clear. If you are unvaccinated, get vaccinated, and particularly in the arena of Omicron if you are fully vaccinated, get your booster shot," he said.

The unvaccinated are eight times more likely to end up in the hospital and 14 times more likely to die compared with people who are fully vaccinated, said White House Covid response coordinator Jeff Zients, citing data from the US Centers for Disease Control and Prevention.

According to CDC Director Rochelle Walensky, 36 states in the US have detected Omicron so far, and the variant makes up about 3 per cent of Covid cases nationwide. However, Omicron infections are likely much higher in New York and New Jersey, she said, making up about 13 per cent of cases.

"Early data suggests that Omicron is more transmissible than delta with a doubling time of about two days," Walensky said.

Sixty-one per cent of Americans are fully vaccinated against Covid and 27 per cent of them have received a booster shot, according to CDC data.

About 68,000 Americans are hospitalised with Covid-19, according to a seven-day average of Department of Health and Human Services data as of Tuesday, up 9 per cent over the previous week and 21 per cent over the last two weeks.