Although the situation varies around the world - in the United States, and much of Europe - the Delta variant remains fully in charge. Here in the United States - based on representative sampling - more than 99% of all recent cases have come back as Delta (see CDC NOWCAST).
How long Delta remains dominant is unknown. Alpha seemed insurmountable 6 months ago, but was swiftly overtaken by Delta in the spring. Whether another variant can usurp Delta's reign remains to be seen.
Since last December - when Alpha was first deemed a threat by the UK - we've been following an ever expanding and shifting list of VOCs (Variants of Concern), VOIs (Variants of Interest), along with a list of lesser variants that various agencies are monitoring.
Yesterday both the CDC and the WHO announced major changes to the classification of known variants, with the WHO (see Weekly Epi Update #58) downgrading 3 VOIs - Eta (B.1.525), Iota (B.1.526) and Kappa (B.1.617.1) - to Variants Under Monitoring (VUMs), stating:
While all three variants carry mutations with suspected and/or established phenotypic impacts, the number of reported detections of these variants have decreased over time at the global, regional and country levels. Evidence from both sequencing data submitted to GISAID and information available to WHO indicate a substantial decline in their respective incidence worldwide, and therefore represent diminished public health risks relative to other VOCs and VOIs.
Individual countries, they note, may continue to list these VUMs as VOIs of local interest. Their VOI list still contains:
The revised list of current VOIs now includes Lambda and Mu variants, both circulating in Latin America, where the Delta variant has begun to circulate but has not yet become dominant. The epidemiology of these VOIs, particularly considering the co-circulation of the Delta variant, will continue to be monitored closely.
Alpha, Beta, Gamma, and Delta remain on the WHO's VOC (Variant of Concern) list.
The CDC yesterday announced a new variant category VBM (Variant Being Monitored) which is the functional equivalent of the WHO's VUM. Wielding a heavy pruning knife, the CDC demoted no fewer than 10 VOIs and VOCs to VBM status (see chart below), leaving only Delta (B.1.617.2 and all AY sublineages) as a Variant of Concern for the United States.
The following excerpt from the CDC's SARS-CoV-2 Variant Classifications and Definitions web page summarizes the changes.
- Genetic lineages of SARS-CoV-2 have been emerging and circulating around the world since the beginning of the COVID-19 pandemic.
- SARS-CoV-2 genetic lineages in the United States are routinely monitored through epidemiological investigations, virus genetic sequence-based surveillance, and laboratory studies.
- The US government SARS-CoV-2 Interagency Group (SIG) added a new class of SARS-CoV-2 variants designated as Variants Being Monitored.
- This class includes variants with substitutions of concern, including previously designated Variants of Interest (VOIs) or Variants of Concern (VOCs), that are no longer detected or are circulating at very low levels in the United States, and as such, do not pose a significant or imminent risk to public health in the United States.
- The SIG Variant classification scheme defines four classes of SARS-CoV-2 variants:
- Variant Being Monitored (VBM)
- Alpha (B.1.1.7, Q.1-Q.8)
- Beta (B.1.351, B.1.351.2, B.1.351.3)
- Gamma (P.1, P.1.1, P.1.2)
- Epsilon (B.1.427 and B.1.429)
- Eta (B.1.525)
- Iota (B.1.526)
- Kappa (B.1.617.1)
- Mu (B.1.621, B.1.621.1)
- Zeta (P.2)
- Variant of Concern (VOC)
- Delta (B.1.617.2 and AY.1 sublineages)
- Alpha (B.1.1.7, Q.1-Q.8), Beta (B.1.351, B.1.351.2, B.1.351.3), and Gamma (P.1,P.1.1, P.1.2) have been downgraded from Variants of Concern to Variants Being Monitored based on significant and sustained reduction in national and regional proportions.
- Eta (B.1.525), Iota (B.1.526), Kappa (B.1.617.1), and B.1.617.3 have been downgraded from Variants of Interest to Variants Being Monitored based on significant and sustained reduction in national and regional proportions.
- Additional Variants Being Monitored include Epsilon (B.1.427 and B.1.429) and Zeta (P.2) based on their previous classification as Variants of Concern or Variants of Interest.
- To date, no variants of high consequence have been identified in the United States.
- Due to the increasing number of sublineages that are associated with Alpha, Delta, and Gamma, unless otherwise specified, CDC will refer to the sublineages collectively as Q sublineages (Alpha), AY sublineages (Delta) and P.1 sublineages (Gamma).
- Laboratory studies suggest that bamlanivimab and etesevimab may be less effective for treating cases of COVID-19 caused by variants with certain substitutions or combinations of substitutions in the spike protein.
- Importantly, the vast majority of Delta variant lineages are sensitive to the combination of bamlanivimab and etesevimab.
- Clinicians seeking advice on the use of monoclonal antibody products authorized for emergency use in the United States for the treatment and prevention of SARS-CoV-2 should consult the NIH COVID-19 Treatment Guidelines
- Vaccines approved and authorized for use in the United States are effective against these variants and effective therapeutics are available. CDC continues to monitor all variants circulating within the United States.
I suspect (but I certainly don't know) that one of the main reasons behind these changes is to get people to concentrate on the immediate threat - which in the United States is clearly Delta - rather than dwell on a long list of variants that may never amount to much.
This may even help vaccine uptake, since endless speculation about the potential future impact of Mu, Lambda, or Gamma in the media have obscured that fact that current vaccines are largely effective against Delta.
Regardless of what category we put them in, emerging COVID variants are going to do whatever they are wont to do. Even when relegated to VBM status, a lot of eyes will remain on these variants, so we are unlikely to be blindsided.
If a recently demoted VOI or VOC begins to make serious inroads, I've no doubt its status will be reevaluated, and elevated if needed.