Americans are urged by health experts to get their COVID-19 vaccines and those who have completed their doses to have their booster shot amid the new increase in virus infections and hospitalizations and the threat of the new Omicron variant.

“Do not wait. Go get your booster if it’s time for you to do so,” said President Joe Biden at the White House recently. “If you are not vaccinated, now is the time to go get vaccinated and to bring your children to go get vaccinated.”

On Monday, the World Health Organization said Omicron posed “very high” global risk because of its mutation, despite that its transmissible potential has not yet been established yet, as well as its impact on the effectiveness of the vaccine and possibility of causing critical illness.

At present, vaccine manufacturers are having the vaccine’ effectiveness amid the concerns on the new variant. This week, it said that it intends to have changes in the vaccines, if needed, to tackle the Omicron variant. This left some of the people questioning the pressure to get a shot if those can be subjected to some tweaks.

“I would strongly suggest you get boosted now, and not wait for the next iteration of it, which we might not even need,” chief medical adviser to the White House Dr. Anthony Fauci told ABC News’ George Stephanopoulos Monday.

He said it is not recommended to wait. “We’ll find out reasonably soon whether higher levels of antibody against the original vaccine that we’ve used, whether or not that can spill over in protection against this.”

His statement was backed with several health experts who also appeal for the people to get vaccinated.

“We don’t have all the answers we want as of yet. In a few weeks, we will know a lot more,” Emory University School of Medicine’s associate professor of medicine in the division of infectious diseases Dr. Colleen Kelley told ABC News.

She said that with the first detected variant, a booster specifically targeting a variant is not necessary as long as the antibody levels were high.

“We hope that this will also be the case with omicron and that high levels of antibodies will maintain some level of protection, but don’t know for sure yet. So, my recommendation is to get boosted now,” Kelley said.

She added that we may not have time to wait for the omicron-specific booster to protect people” if the newly-found variant is proved to be highly infectious.

Omicron variant was not detected in the U.S. as of Tuesday but experts said it might be already in the localities.