The World Health Organization has added the "mu" strain to its list of COVID-19 "variants of interest."
The strain, also know as B.1.621, was first documented in Colombia in January 2021 but didn’t receive an official designation until Aug. 30.
According to a WHO report, the mu variant shows signs of evading COVID-19 vaccine protection.
"The Mu variant has a constellation of mutations that indicate potential properties of immune escape," the report said.
WHO officials said the mu strain has appeared in 39 countries with sporadic outbreaks in South America and Europe. However, the strain makes up less than 0.1% of COVID-19 cases worldwide.
WHO defines variants of interest as those COVID-19 strains having the potential of affecting the virus’ transmissibility, and disease severity and could be responsible for outbreaks or surges in cases in multiple countries over time. However, further research is needed.
Other variants of interest include eta, iota, kappa and lambda.
Variants of interest are different from variants of concern where designated strains are known to have increased transmissibility and can cause decreased effectiveness in public health measures such as the COVID-19 vaccine.
Variants of concern include the United Kingdom, South African and delta variants.
Meanwhile, the delta variant continues to fuel COVID-19 surges across the U.S. and worldwide. The U.S. is averaging more than 155,000 new coronavirus cases and 1,200 deaths per day, and several U.S. states have more COVID-19 patients in the hospital now than at any other time during the pandemic.
The U.S. gave full approval to Pfizer’s COVID-19 vaccine Aug. 23, opening the way for more universities, companies and local governments to make vaccinations mandatory. Moderna has also applied to the Food and Drug Administration for full approval of its vaccine. Johnson & Johnson, maker of the third COVID-19 vaccine option in the U.S., said it hopes to do so later this year.
Moderna and Johnson & Johnson vaccines are currently approved for emergency use.
According to the CDC, more than 174 million Americans are fully vaccinated, representing 52.6% of the country's total population.
The Associated Press contributed to this report. This story was reported from Los Angeles.