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How long does spike protein remain in the body after COVID recovery?
Executive Summary
The available analyses show no single consensus: most people clear spike protein within weeks to a few months after infection or vaccination, but multiple studies detected spike or spike antigens lingering in a minority of individuals for many months — in some reports up to 31 months post‑infection or ~600–700 days post‑vaccination. The findings vary by study design, the substance measured (free spike protein in blood vs. tissue‑restricted antigen), and the population studied (general recovered people vs. those with post‑COVID conditions), so claims that spike is always gone within days or always persists for years are both contradicted by the assembled evidence [1] [2] [3] [4].
1. Why studies disagree: methods change the story and explain conflicting headlines
The key reason for divergent claims is different detection methods and targets. Some analyses measured transient spike protein in blood after mRNA vaccination and reported clearance within weeks, reflecting the immune response to vaccine‑produced antigen [1] [5]. Other investigations used ultrasensitive assays or tissue sampling and reported detectable spike antigen or fragments months to years later; one study found measurable spike in serum between 4 and 31 months after acute infection in a minority of participants, while a separate preprint described detectable antigen up to roughly 600–700 days after vaccination in some people [2] [3]. These methodological differences—assay sensitivity, whether measuring full spike vs. fragments, blood vs. tissue sampling, and cohort selection—drive the disparate conclusions rather than a single unified biological timeline.
2. What the bulk of evidence says about typical clearance after infection or vaccination
Most clinical and public‑health sources document that for the majority of people, spike protein and vaccine‑produced antigen are cleared quickly, typically within days to weeks, as antibodies and cellular immunity remove circulating antigen [1]. Clinical series and guidance note that lingering antigen is not the norm and that acute infection usually triggers a time‑limited antigenemia. However, clinical reports and reviews also document that antigens can linger in tissues or be intermittently detectable in blood for much longer in a minority of cases, so the typical course is rapid clearance but with documented exceptions linked to individual biology or disease sequelae [4] [5].
3. Persistence in a minority: months to years in selected studies
Several recent studies report long‑term detection of spike or spike fragments in a subset of individuals. A February 2025 study detected spike in 11% of recovered healthy controls and up to 14% among certain post‑COVID syndrome patients between 4 and 31 months post‑infection, and a separate preprint reported antigen detectability roughly 600–700 days after vaccination in some participants [2] [3]. These findings show persistence is possible but not ubiquitous, and the concentration or mere detectability did not consistently correlate with time since infection or vaccination, indicating individualized persistence patterns rather than a simple decay curve [2].
4. Clinical implications: association with long COVID, but causality is unsettled
Some reviews and clinical analyses link persistent spike antigen to post‑acute sequelae (long COVID) and multi‑system symptoms, suggesting a plausible pathophysiologic mechanism involving ongoing immune activation or tissue injury [4] [6]. Yet other studies fail to show a consistent relationship between detectable spike in serum and clinical syndromes, and authors caution that detection alone does not establish causation; persistent antigen could be a marker of underlying processes rather than the direct driver of symptoms [2] [4]. The evidence therefore supports further targeted research into whether and how antigen persistence contributes to chronic post‑infectious conditions.
5. Read the fine print: what to watch for and how to interpret future claims
Interpretation requires attention to who was studied, what was measured, and when. Claims that spike disappears within 24–48 hours oversimplify mRNA vaccine biology and rely on short‑window blood sampling or less sensitive assays [7] [1]. Conversely, headlines asserting universal multi‑year persistence typically derive from small cohorts or preprints and need peer review and replication [3]. Policymakers and clinicians should weigh assay sensitivity, cohort selection, and peer‑review status; researchers should prioritize standardized, longitudinal sampling and tissue correlation to clarify how common and clinically meaningful long‑term antigen persistence truly is [2] [5].