Chronic inflammation may cause long COVID — and could be the secret to treatment, new study says

Researchers at Beth Israel Deaconess published evidence in Nature Immunology that chronic inflammation — with persistent activation of several inflammatory pathways, notably the JAK‑STAT pathway — is a key contributor to long COVID, offering an alternative or complementary mechanism to the viral‑reservoir hypothesis. In two cohorts totaling 180 patients they observed sustained inflammatory signaling for more than six months and have opened a clinical trial repurposing the JAK inhibitor abrocitinib; prior small studies of antivirals such as Paxlovid have shown no clear therapeutic benefit. Although sample sizes are modest and further validation is needed, the findings point to immediately actionable therapeutic opportunities using approved anti‑inflammatory drugs, particularly for symptoms like brain fog and fatigue.

Analysis

Researchers at Beth Israel Deaconess published data in Nature Immunology showing persistent, elevated chronic inflammation in long COVID patients across two cohorts (142 patients enrolled early in the pandemic and a 38-patient confirmatory cohort, total n=180), with blood-plasma and cellular assays at acute infection, 90–180 days, and >180 days demonstrating sustained activation of several inflammatory pathways for more than six months. The JAK-STAT signaling pathway was identified as one of the most activated inflammatory cascades; investigators have launched a clinical trial repurposing the approved JAK inhibitor abrocitinib, citing the advantage that anti-inflammatory drugs are already available for rapid clinical testing. This inflammatory-pathway hypothesis is positioned as an alternative or complementary mechanism to the viral-reservoir theory; the article notes that the first three published Paxlovid antiviral studies showed no therapeutic efficacy, strengthening the rationale to pursue anti-inflammatory strategies. Key limitations are modest sample sizes and the heterogeneous clinical definition of long COVID (no diagnostic blood test); therefore clinical-readout and regulatory outcomes will be the primary near-term determinants of whether these findings translate into approved treatments or broader clinical adoption.

Key Decisions for Investors

• Monitor the abrocitinib trial closely for primary endpoint timing and effect size because a positive readout would be an immediate commercial and clinical catalyst
• Consider selective exposure to companies with marketed or late-stage JAK-STAT inhibitors and developers of anti-inflammatory therapeutics, while avoiding broad allocation until larger randomized trials validate efficacy
• Maintain conservative position sizing and hedge potential binary outcomes given the small cohorts and diagnostic uncertainty, and be prepared to reduce conviction if larger studies fail to replicate the persistent-inflammation signal
• Track regulatory signals, diagnostic development and payer commentary on long COVID therapies, and continue to discount the near-term commercial case for antivirals given early Paxlovid studies showing no therapeutic benefit