A new warning has emerged over a COVID-19 variant that ripped through a Kentucky nursing home and infected 46 people, most of whom were vaccinated.

Three people died in the cluster, the Louisville Courier-Journal reported.

The March spike has now been attributed to a variant of the virus that emerged in Japan and had evolved to circumvent the protection given by existing vaccines, according to Newsweek.

An investigation by the Kentucky Department of Public Health revealed that one staff member, who was not vaccinated, infected others.

Former Harvard Medical School professor William Haseltine wrote in Forbes that the new variant is called R.1.

After first being document, R.1 has infected more than 10,000 people around the world.

The variant includes five mutations.

“R.1 is a variant to watch,” Haseltine wrote. “It has established a foothold in both Japan and the United States.

“In addition to several mutations notably in the spike and nucleocapsid protein in common with variants of concern, R.1 has a set of unique mutations that may confer an additional advantage in transmission, replication, and immune suppression.”

Dr. Kevin Kavanagh, chairman of the nonprofit health advocacy organization Health Watch USA, told the Courier-Journal that as more variants develop and spread, vaccination will not be a cure-all to ward off the disease. The delta variant, which is now infecting people across America, is an example of one variant that spread rapidly.

A federal Centers for Disease Control and Prevention report written on the incident said that “Although the R.1 variant is not currently identified as a CDC variant of concern or interest, it does have several mutations of importance.”

The CDC report said that four potential reinfections were identified, “providing some evidence of limited or waning natural immunity to this variant.”

White House adviser Dr. Anthony Fauci said this week that the potential of a so-called “monster variant” exists, the New York Daily News reported.

“There’s always a risk of, as you get more circulation of the virus in the community, that you’ll get enough accumulation of new mutations to get a variant substantially different than the ones we’re seeing now,” he said.

“You’re vaccinating now to prevent the next mutant coming, the next variant from coming.”

But he admitted that emerging variants could be immune to the vaccines.

“Then it would in many respects negate some of the very positive protection that you get from the vaccines,” Fauci said.