COVID-19 Cases Rise as Omicron-Derived FLiRT, LB.1 Variants Take Hold
Updated vaccines are expected to be available in the coming months.
Barbecues, beach vacations, and… COVID-19? The new hallmark of summer may be the annual surge in COVID-19 cases. Cases have been rising for several weeks and are likely higher than current reports suggest due to the significant scaling back of disease surveillance since the public health emergency was ended in May 2023.
As of July 9, the CDC estimates that “COVID-19 infections are growing or likely growing in 45 states and territories,1 compared with early spring 2024 which had far fewer infections and hospitalizations than the previous winter.2
COVID-19 cases are once again on the rise. | Image credit: oz - stock.adobe.com
“The virus tends to replicate well and stay alive in an environment with warm and moist conditions,” said Robert H. Hopkins, Jr., MD, medical director of the National Foundation for Infectious Diseases, in an interview with CNN.2 “That’s fits with what we’re seeing.” Hopkins spoke with CNN for an article published on June 28. Since then, record high temperatures and heatwaves have continued to blanket much of the United States.3
FLiRT Variants Take Center Stage
The current SARS-CoV-2 subvariant spreading is referred to as the FLiRT variant. In early March, the strain—KP.2—was responsible for approximately 4% of US COVID-19 infections compared with its parental strain, JN.1. But by early May, KP.2 surpassed JN.1 as the dominant strain, representing approximately 28% of infections.4
“FLiRT” is the name for “a whole family of variants—including KP.2, JN.1.7, and any other variants with KP or JN—that appear to have independently picked up the same set of mutations,” said Andrew Pekosz, PhD, a professor of Molecular Microbiology and Immunology at the Johns Hopkins Bloomberg School of Public Health in a Q&A published on the university’s website.4 “The particular mutations that people refer to as ‘FLiRT’s or ‘FLip’s refer to specific positions in the spike protein—in this case, positions 456, 346, and 572.”
READ MORE: Post–COVID-19 Condition: The Frustrating Fight for Recognition and Treatment
By the beginning of June, the LB.1 variant began its circulation as well. This variant—also part of the Omicron family—is an offshoot of JN.1 and is closely related to the FLiRT variants, albeit with an additional mutation (S:S31del). According to the Infectious Disease Society of America, these variants may also be referred to as “deFLiRT,” a nod to its additional deletion.5
Experts suspect that LB.1, “and another variant called KP.2.3, which also has the 2 FLiRT mutations plus an additional one, may be more transmissible,” said Scott Roberts, MD, an infectious disease specialist at Yale Medicine, in a Q&A.6 However, there are no indications as of yet that LB.1 is more transmissible than the circulating FLiRT variants—and all current variants appear to cause milder disease than the variants that circulated at the start of the pandemic.
Vaccine Updates
As with every evolution of the SARS-CoV-2 virus, one of the biggest concerns is the effectiveness of currently available COVID-19 vaccines against new variants. Previous iterations of the vaccine focused on the then-dominant XBB.1.5 variant, but changes in the spike proteins mean that immunity from prior vaccinations may be lacking.
“This variant can evade the immune response more effectively than prior versions of the virus, said Matthew J. Binnicker, PhD, director of the Clinical Virology Laboratory at the Mayo Clinic.7 “If you’ve been infected, or you’ve been vaccinated, and you’ve got some antibodies in your system, those antibodies may not recognize the protein on the surface of the virus as well.”
“With this latest round of variants…the antibodies from past vaccination may not bind and neutralize the virus as well,” Binnicker added.
READ MORE: CDC, ACIP Announce Vaccine Recommendations and Updates
The World Health Organization announced in April that the agency’s Technical Advisory Group on COVID-19 Vaccine Composition had advised monovalent vaccines focused on the JN.1 lineage for the next iteration of COVID-19 vaccines.8 In June, the FDA’s Vaccines and Related Biological Products Advisory Committee echoed this view, voting unanimously to recommend a monovalent JN.1-lineage vaccine composition for the 2024-2025 formulation of COVID-19 vaccines.9
Spikevax manufacturer Moderna submitted an FDA application for its 2024-2025 vaccine formulation targeting JN.1. The company is submitting data to global regulatory authorities “to support registration and supply of the 2024-2025 formula of Spikevax in time for the upcoming vaccination season.”10
Pfizer and BioNTech have also developed an updated version of Comirnaty, focused on the JN.1 lineage. An application has been submitted to the Committee for Medicinal Products for Human Use at the European Medicines Agency. The companies have started rolling applications with the FDA as well, “requesting approval of their Omicron KP.2-adapted monovalent COVID-19 vaccines for individuals 6 months of age and older.”11
Novavax—which manufactures the only non-mRNA COVID-19 vaccine, instead offering a protein-based shot using the company’s Matrix-M adjuvant—has submitted an amendment to its current FDA Emergency Use Authorization for the updated 2024-2025 formulation targeting JN.1 (NVX-CoV2705). The vaccine has, according to the company, “demonstrated broad cross-neutralizing antibodies against multiple variant strains, including KP.2 and KP.3.”12
Updated COVID-19 vaccines are expected to be ready in time for the 2024-2025.
READ MORE: COVID-19 Resource Center
References
COVID-19 and infleunza growth estimates. CDC. July 12, 2024. Accessed July 15, 2024. https://www.cdc.gov/forecast-outbreak-analytics/about/rt-estimates.html
McPhillips D. A summer wave of COVID-19 has arrived in the US. CNN. June 28, 2024. Accessed July 15, 2024. https://www.cnn.com/2024/06/28/health/covid-summer-wave/index.html
Golembo M. East coast braces for record heatwave: Latest forecast. ABC News. July 15, 2024. Accessed July 15, 2024. https://abcnews.go.com/US/east-coast-braces-record-heat-wave/story?id=111954637
Katella K. 3 things to know about FLiRT and LB.1, the new coronavirus strains. Yale Medicine. Updated July 11, 2024. Accessed July 15, 2024. https://www.yalemedicine.org/news/3-things-to-know-about-flirt-new-coronavirus-strains
Rosen A. What to know about COVID FLiRT variants. Johns Hopkins Bloomberg School of Public Health. May 13, 2024. Accessed July 15, 2024. https://publichealth.jhu.edu/2024/what-to-know-about-covid-flirt-variants
COVID-19 variant update. Infectious Disease Society of America. July 10, 2024. Accessed July 15, 2024. https://www.idsociety.org/covid-19-real-time-learning-network/diagnostics/covid-19-variant-update/#/+/0/publishedDate_na_dt/desc/
Balzer D. A Mayo Clinic virologist explains FLiRT and why you may need a new COVID-19 vaccination. Mayo Clinic. May 30, 2024. Accessed July 15, 2024. https://newsnetwork.mayoclinic.org/discussion/a-mayo-clinic-virologist-explains-flirt-and-why-you-may-need-a-new-covid-19-vaccination/
Statement on the antigen composition of COVID-19 vaccines. News release. World Health Organization. April 26, 2024. Accessed July 15, 2024. https://www.who.int/news/item/26-04-2024-statement-on-the-antigen-composition-of-covid-19-vaccines
Updated COVID-19 vaccines for use in the United States beginning fall 2024. FDA. June 13, 2024. Accessed July 15, 2024. https://www.fda.gov/vaccines-blood-biologics/updated-covid-19-vaccines-use-united-states-beginning-fall-2024
Moderna files FDA application for the JN.1 targeting COVID-19 vaccine. News release. Moderna. June 7, 2024. Accessed July 15, 2024. https://investors.modernatx.com/news/news-details/2024/Moderna-Files-FDA-Application-for-the-JN.1-Targeting-COVID-19-Vaccine/default.aspx
Pfizer and BioNTech receive positive CHMP opinion for Omicron JN.1-adapted COVID-19 vaccine in the European Union. News release. Pfizer. June 27, 2024. Accessed July 15, 2024. https://www.pfizer.com/news/press-release/press-release-detail/pfizer-and-biontech-receive-positive-chmp-opinion-omicron-3
Novavax submits application to US FDA for updated protein-based 2024-2025 formula COVID-19 vaccine. News release. Novavax. June 14, 2024. Accessed July 15, 2024. https://ir.novavax.com/press-releases/2024-06-14-Novavax-Submits-Application-to-U-S-FDA-for-Updated-Protein-based-2024-2025-Formula-COVID-19-Vaccine
