(NEXSTAR) – The World Health Organization has identified another coronavirus variant that may have the ability to evade vaccine protections.

The B.1.621 variant, also known as the “mu” variant, was first identified in Colombia in January 2021. WHO officially labeled mu as a variant of interest (VOI) on Aug. 30, according to its Weekly Epidemiological Update published Tuesday.

“The Mu variant has a constellation of mutations that indicate potential properties of immune escape,” the organization wrote, noting that vaccinated individuals appear to show a “reduction in neutralization capacity” against mu. WHO added that these “potential properties” may have similarities to those observed in the beta variant.

As of Tuesday, WHO indicated there were only “some” reports of larger outbreaks of mu, specifically in South America and Europe, along with “a few sporadic reports of cases.”

In total, WHO says the variant has been reported in 39 countries. But its prevalence has “consistently increased” in Colombia and Ecuador, despite reports of sequenced cases dropping globally overall.

WHO said further studies are needed to determine the characteristics of the mu variant.

As an official variant of interest (VOI), mu joins WHO’s list of variants that have been determined to exhibit “genetic changes that are predicted or known to affect virus characteristics” including transmissibility, immune escape, disease severity or resistance to treatment. VOIs are also defined as variants that can cause significant transmission in multiple countries with “increasing number of cases over time,” among other properties.

Other VOI being monitored by WHO include eta, iota, kappa and lambda.

Variants of concern (VOC), meanwhile, include the alpha, beta, gamma and delta variants. According to WHO, a VOC is a variant that meets the criteria for a VOI, but is associated with either an increase in virulence, a decrease in effectiveness of public health measures, or a  “detrimental change in COVID-19 epidemiology,” as well as other factors.