Long COVID Research Update: FLINTLOCK, Viral Persistence, and the Search for Effective Treatments
It’s been approximately seven months since the last update to this petition, and several important developments in Long COVID research deserve attention.
FLINTLOCK: An Encouraging Step Forward
On October 27, 2026, the FLINTLOCK Phase 2 clinical trial, developed by Invivyd in collaboration with the SPEAR Study Group, was officially registered on ClinicalTrials.gov.
The study will investigate VYD2311, a next-generation monoclonal antibody, in approximately 130 participants with Long COVID or post-vaccination syndrome. The trial is currently listed as not yet recruiting. [1]
This is encouraging progress, and the researchers working to make it possible deserve recognition.
However, emerging evidence suggests that treating Long COVID may require more than neutralizing antibodies alone.
What Recent Research Is Revealing
An August 2026 study from UCSF detected SARS-CoV-2 material in intestinal tissue from a subset of Long COVID patients, alongside substantial immune dysfunction and abnormalities in pathways involved in recognizing and clearing infected cells. [2]
A separate 2026 study published in Mucosal Immunology also identified elevated SARS-CoV-2 nucleocapsid protein in intestinal tissue from patients with post-COVID syndrome, alongside altered natural killer (NK) cell populations, increased mast-cell activity, and other signs of local immune dysregulation. [10]
Earlier PET imaging research identified persistent T-cell activation across multiple tissues, including the gut, lungs, bone marrow, brainstem, and spinal cord. Researchers also detected SARS-CoV-2 RNA in intestinal biopsies. [3]
More recently, an October 2026 study identified persistently activated SARS-CoV-2-specific CD8 T cells in the blood of some Long COVID patients, with evidence of impaired function and ongoing antigen-driven stimulation. [4]
Importantly, a 2023 study published in Nature Immunology demonstrated that replication-competent SARS-CoV-2 could persist in lung macrophages of infected macaques for more than six months. Researchers also identified mechanisms involving interferon-gamma and NK cells that influenced viral persistence and immune clearance. Although these findings come from an animal model, they provide valuable insight into how infected cells might evade elimination. [13]
Together, these studies strengthen the rationale for investigating tissue-based viral persistence and impaired immune clearance, although they do not establish that replication-competent virus persists in every person with Long COVID or causes all symptoms. The August and October 2026 preprints are also awaiting peer review.
Meanwhile, randomized clinical trials of the monoclonal antibody AER002 and extended Paxlovid treatment have not demonstrated significant overall clinical benefit. [5,6]
These results raise an important question: Are current treatments sufficiently matched to the underlying biological mechanisms?
Moving Toward Mechanism-Matched Treatments
A 2025 review published in The Lancet Infectious Diseases, Targeting the SARS-CoV-2 Reservoir in Long COVID, emphasized the importance of identifying reservoir mechanisms, selecting appropriate participants, developing reliable biomarkers, and investigating potential combination treatments. [11]
Different forms of viral persistence may require fundamentally different therapeutic approaches.
A framework worth exploring in future clinical trials includes:
• Ongoing viral replication: Direct-acting antivirals such as remdesivir or ensitrelvir, potentially combined with pegylated interferon-lambda to strengthen intracellular antiviral defenses.
• Persistently infected cells: SARS-CoV-2-specific cytotoxic T-cell therapies such as TVGN-489, developed by Tevogen Bio, could potentially recognize and eliminate infected cells displaying viral antigens. Early clinical research has demonstrated feasibility in acute COVID-19, but efficacy in established Long COVID remains unknown. [8]
• Infected cells evading immune recognition: A 2025 study demonstrated that SARS-CoV-2’s Nsp1 protein can suppress HLA class I and II expression, potentially impairing the ability of T cells to recognize infected cells. [12] This raises the possibility that some reservoirs could evade conventional cytotoxic T-cell responses. NK-cell-directed approaches may therefore deserve investigation. Anktiva (N-803), an IL-15 receptor agonist that stimulates NK cells and CD8 T cells, is already being investigated in the Phase 2 INTERRUPT-LC study at UCSF. [9] However, NK-cell activation alone may not overcome every form of immune evasion.
• Antibody-mediated elimination of infected cells: Monoclonal antibodies capable of recruiting immune cells to destroy infected cells through antibody-dependent cellular cytotoxicity (ADCC) could represent another avenue, provided the relevant viral proteins remain accessible on the cell surface.
• Persistent intracellular viral RNA: Future RNA-targeting technologies, including siRNA and antisense oligonucleotides, could potentially address forms of viral persistence that conventional antivirals cannot effectively target.
These approaches remain experimental for SARS-CoV-2 reservoir clearance, and none has been proven to eradicate persistent reservoirs in people with Long COVID.
The goal should be to develop biomarker-guided clinical trials that identify what is persisting, where it is located, whether it is replicating, and whether infected cells remain recognizable to the immune system.
Carefully designed combination therapies may ultimately prove more effective than targeting individual mechanisms in isolation.
Autoimmunity May Be Another Important Piece
Viral persistence is not the only mechanism deserving investigation.
A May 2026 study published in Cell demonstrated that transferring antibodies from Long COVID patients into mice could produce neurological abnormalities, pain-related changes, and fatigue-like behaviours. [7]
These findings strengthen the case for investigating autoimmune mechanisms in certain patient subgroups.
Targeted approaches, including IVIG and B-cell-directed therapies, warrant further investigation where there is credible evidence of pathogenic autoimmunity, although benefits in Long COVID remain unproven and some controlled antibody-directed trials have produced negative results.
Importantly, viral persistence and autoimmunity may not be mutually exclusive. Persistent viral antigens could theoretically contribute to ongoing immune dysfunction and autoimmune responses.
Understanding these relationships may be essential to developing treatments that produce lasting recovery.
Canada Must Be Part of the Solution
The central purpose of this petition remains unchanged.
Canada needs better access to protective COVID-19 monoclonal antibodies for vulnerable individuals and meaningful public investment in clinical trials investigating the biological causes of Long COVID.
This includes research into persistent viral reservoirs, targeted antivirals, cellular immunotherapies, autoimmune mechanisms, and carefully selected combination treatments.
We need clinical trials that go beyond measuring symptoms alone, investigate whether proposed disease mechanisms are actually being corrected, and establish whether meaningful, lasting recovery is possible.
FLINTLOCK represents an important step forward. Hopefully, it will also help accelerate a broader effort to develop treatments directed at the underlying biology of Long COVID.
Canada must also acknowledge that COVID-19 remains an ongoing public-health threat, rather than treating the pandemic and its consequences as problems of the past. Continued transmission, reinfections, and the risk of Long COVID demand sustained public-health action, including improved indoor air quality, accessible vaccines and preventive treatments, transparent surveillance, and greater investment in biomedical research. Canada should be helping lead these efforts, ensuring that vulnerable populations are protected and that preventing new cases of Long COVID remains a national priority.
Thank you to everyone who continues to support and share this petition.
With gratitude,
Rowan
References & Clinical Trials
1. FLINTLOCK Phase 2 Trial — VYD2311 (ClinicalTrials.gov, 2026)
https://clinicaltrials.gov/study/NCT07899346
2. Multiomic and Spatial Profiling of Colorectal Tissue Reveals Viral Persistence and Immune Dysregulation in Long COVID (bioRxiv, August 2026 — preprint)
https://doi.org/10.64898/2026.08.07.743616
3. Tissue-Based T Cell Activation and Viral RNA Persist for Up to 2 Years After SARS-CoV-2 Infection (Science Translational Medicine, 2024)
https://doi.org/10.1126/scitranslmed.adk3295
4. Persistently Activated Virus-Specific CD8 T Cells Indicate Antigen-Driven Immune Aberrations in Long COVID (bioRxiv, October 2026 — preprint)
https://doi.org/10.64898/2026.10.14.759221
5. SARS-CoV-2-Specific Monoclonal Antibody AER002 in Long COVID: An Exploratory Randomized Phase 2a Mechanistic Trial (Nature Communications, September 2026)
https://doi.org/10.1038/s41467-026-77925-y
6. Nirmatrelvir-Ritonavir Targeting Viral Persistence in Long COVID: RECOVER-VITAL (The Lancet Infectious Diseases, August 2026)
https://doi.org/10.1016/S1473-3099(26)00406-8
7. A Causal Link Between Autoantibodies and Neurological Symptoms in Long COVID (Cell, May 2026)
https://doi.org/10.1016/j.cell.2026.04.042
8. Safety and Feasibility of Third-Party Cytotoxic T Lymphocytes for High-Risk Patients With COVID-19 — TVGN-489 (Blood Advances, 2024)
https://doi.org/10.1182/bloodadvances.2024013344
9. INTERRUPT-LC Phase 2 Trial — Anktiva (N-803) for Long COVID (ClinicalTrials.gov)
https://clinicaltrials.gov/study/NCT07108036
10. Persistent Gut-Immune Axis Dysregulation in Long-Term Post-COVID Syndrome (Mucosal Immunology, 2026)
https://doi.org/10.1016/j.mucimm.2026.03.002
11. Targeting the SARS-CoV-2 Reservoir in Long COVID (The Lancet Infectious Diseases, 2025)
https://doi.org/10.1016/S1473-3099(24)00769-2
12. SARS-CoV-2 Nsp1 Is a Major Suppressor of HLA Class I and Class II Expression (Viruses, August 2025)
https://doi.org/10.3390/v17081083
13. SARS-CoV-2 Viral Persistence in Lung Alveolar Macrophages Is Controlled by IFN-γ and NK Cells (Nature Immunology, November 2023)