New COVID-19 Variants, FDA Approvals for Booster Doses on the Horizon

Although the Delta variant remains the dominant strain within the United States, the Mu and C.1.2 variants are being acknowledged as they are beginning to take hold internationally in some countries.

In their weekly epidemiological update, the WHO discussed a newly classified VOI, the Mu (B.1.621) strain. Mu was first discovered in Columbia in January of this year, and the variant has seen sporadic reporting of cases throughout the world. It has mostly been concentrated in South American and Europe.

“As of 29 August, over 4500 sequences (3794 sequences of B.1.621 and 856 sequences of B.1.621.1) have been uploaded to GISAID from 39 countries,” the WHO wrote in its report. “Although the global prevalence of the Mu variant among sequenced cases has declined and is currently below 0.1%, the prevalence in Colombia (39%) and Ecuador (13%) has consistently increased.”

The WHO did acknowledge the variant had potential properties of immune escape. “Preliminary data presented to the Virus Evolution Working Group show a reduction in neutralization capacity of convalescent and vaccine sera similar to that seen for the Beta variant, but this needs to be confirmed by further studies,” the WHO report stated.

Yesterday, the White House COVID-19 Response Team and federal public health officials held a press conference on the US pandemic response efforts. Anthony Fauci, MD, director of the National Institutes of Allergy and Infectious Diseases (NIAID) and chief medical advisor to the Biden Administration said although the Mu variant was not a threat to the United States right now, they were closely monitoring it.

C.1.2 Variant

This variant was discovered in South Africa in May of this year. A preprint study said the variant has been detected in 6 of the 9 provinces in the country and also been found in China, England, Switzerland, Portugal, New Zealand, the Democratic Republic of the Congo, and Mauritius

The Lambda variant is the closest phylogenetically to C.1.2, but the South African strain appears to have distinct mutations.

The study’s authors stated the C.1.2 may be present in other areas of South Africa that are not sampled as frequently for the strain and there may be an underrepresentation of the variant in both the country and internationally.

“…We see consistent increases in the number of C.1.2 genomes in South Africa on a monthly basis, where in May C.1.2 accounted for 0.2% (2/1054) of genomes sequenced, in June 1.6% (25/2177) and in July 2.0% (26/1326), similar to the increases seen in Beta and Delta in South Africa during early detection,” the study’s authors wrote.

The WHO has not yet elevated C.1.2 to a VOI, and Maria Van Kerkhove, PhD, WHO COVID-19 technical lead, tweeted earlier this week that there were only approximately 100 cases of C.1.2 reported globally and that it did not appear to be showing an upward circulation trend. However, she did caution in the same tweet that more sequencing needed to be done.

Approval Possibilities

As previously reported, September appears to be an important month for COVID-19 vaccine boosters in the United States. This week demonstrated continued moves on this front. On Wednesday, Moderna announced it has submitted data to the FDA for approval for a booster dose of its COVID-19 vaccine, mRNA-1273.

“Our submission is supported by data generated with the 50 µg dose of our COVID-19 vaccine, which shows robust antibody responses against the Delta variant,” Moderna CEO Stéphane Bancel said in a statement.

No timeline has been set yet for discussion of this booster dose by the FDA.

On the same day, the FDA announced it was planning its next VRBPAC meeting on September 17 to discuss the supplemental Biologics License Application (sBLA) for the booster dose of the BNT162b2 (Comirnaty) Pfizer-BioNTech vaccine that was submitted last week. The 2 companies are seeking marketing and prescribing of a third booster dose of the vaccine for fully vaccinated individuals aged 16 years and older.

“A transparent, thorough and objective review of the data by the FDA is critical so that the medical community and the public continue to have confidence in the safety and effectiveness of COVID-19 vaccines. The FDA will review the supplemental application as expeditiously as possible, while still doing so in a thorough and science-based manner,” Peter Marks, MD, PhD, director of the FDA’s Center for Biologics Research and Evaluation, said in a statement.

The evolution of COVID-19 morphing into new variants is certainly concerning and something public health officials will need to remain vigilant in monitoring. At the same time, full FDA approvals for booster doses appears to be a paramount strategy for preventing the virus in the US. And, if the recent past proves anything in terms of the FDA's approach to vaccines, it is likely booster doses will be approved by the federal government in the coming weeks.