COVID NOW: Should We Worry About the Mu Variant?

Words by Daniela Cortes

Cover Photo Chosen by Kazi Maisha

Edited by Fabliha Hussain and Kazi Maisha

The Mu variant is the newest “variant of interest” that the World Health Organization (WHO) is studying. The Mu variant, also known as B.1. 621, was first identified in Columbia in February 2021. Since then, it has propagated in 48 countries with 10 of these countries having Mu cases just this month. Columbia continues to have the highest amount of Mu COVID cases. The variant has also been detected in the United States in the last four weeks. Although more Mu cases have been reported in every state, the variant still represents less than 0.2% of new infections. According to Dr. Anthony Fauci during the September 2nd White House Press Briefing, the CDC is keeping a close eye on it, but the Mu variant is not considered an immediate threat at this moment. In fact, Dr. Fauci asserted that the Delta variant is more than 99% dominant in the United States.

So, why is Mu still considered a variant of interest?

A Columbian study showed that Mu is 1.2 times more transmissible than the original COVID strain while the Delta variant is 2 times more transmissible than the original strain. The WHO is more concerned about the variant resisting vaccine protection. The WHO’s Maria Van Kerkhove said that Mu “is of interest to us because of the combination of mutations it has. But it doesn’t seem to be circulating.” In the White House Press Briefing, Dr. Fauci stated that the Mu variant mutations “suggests that it would evade certain antibodies—not only monoclonal antibodies but vaccine and convalescent serum-induced antibodies—but there isn't a lot of clinical data to suggest that. It is mostly laboratory, in vitro data.” Dr. Fauci, however, is still urging Americans to be vaccinated, stating that, “even when you have variants that do diminish, somewhat, the efficacy of a vaccine—the vaccines still are quite effective against variants of that type.”

With Delta continuing to dominate cases in the United States, the CDC is focusing its efforts on vaccinating Americans to prevent the spread of infection. Booster vaccines are also being studied and tested due to waning immunity among those who were vaccinated earlier in the year. According to the CDC, “the goal (once receiving FDA and ACIP approval) is for people to start receiving a COVID-19 booster shot beginning in the fall, with individuals being eligible starting 8 months after they received their second dose of an mRNA vaccine” in order to combat new variants like Mu that affect vaccine efficacy. During the press briefing, Dr. Fauci states that a “full regimen for vaccination will likely be three doses . . . when you give a prime and maybe a second shot as a boost—but give the immune system enough chance to mature, in both affinity maturation and maturation of the B cell repertoire. . . I believe we have good reason to believe—that that only will not be a strong response, but that it will actually be durable.” With studies and tests still being conducted, the CDC hopes to give booster shots first to those who were eligible to receive a COVID-19 vaccine in early 2021, including healthcare providers, residents of long-term care facilities, and other older adults, to continue to fight the Delta variant.