How long is spike protein detectable in blood after mRNA COVID vaccines specifically?
Executive summary
Studies report detectable vaccine-derived spike protein or its mRNA in blood or tissues from a few days up to roughly 6 months in some subjects; specific reports find S1/spike detectable in plasma up to 14–28 days (small cohorts) and isolated studies reporting detection of recombinant spike fragments or spike in monocytes between about 69 and 245 days, with a maximum reported blood detection of 187 days in one proteomics study (minimum 69 days) [1] [2] [3] [4] [5]. Multiple reviewers and primary studies also document vaccine mRNA and spike protein in axillary lymph nodes up to 60 days [6] [7].
1. Short-term kinetics: spike/S1 usually clears in days–weeks
Early, small human studies using ultrasensitive assays found the S1 subunit and occasional full spike in plasma soon after injection, peaking within about 1–5 days and generally falling below detection by two weeks; one series of 13 Moderna recipients found S1 in 11/13 as early as day 1, S1 peaked ~day 5 and was undetectable by day 14, while full spike appeared in 3/13 participants at an average of 15 days and was not seen after the second dose [1]. Another study reported vaccine mRNA persisting in plasma for at least two weeks, consistent with short-term systemic presence [3].
Evidence summary: most controlled, early-timepoint studies show spike/S1 or vaccine mRNA is detectable within days and typically declines to undetectable levels within roughly 1–4 weeks in ordinary cohorts [1] [3].
2. Medium-term tissue persistence: lymph nodes and biopsies up to ~60 days
Multiple groups found vaccine mRNA and spike protein in axillary lymph nodes well beyond the first weeks: immunohistochemistry and in situ hybridization in human axillary node biopsies detected spike and vaccine mRNA up to 60 days after vaccination with BNT162b2 or mRNA-1273 [6] [7]. These findings reflect local tissue retention rather than continuous high plasma levels and are consistent across reviews and targeted biopsy reports [6] [7].
Implication: the immune system’s local response and LNP trafficking can prolong antigen/mRNA presence in lymphoid tissue even after plasma levels fall [2] [6].
3. Longer detections in selected studies and symptomatic cohorts: up to months
A proteomics study using mass spectrometry reported detection of a recombinant, proline-stabilized “PP-Spike” fragment with minimum and maximum detection times of 69 and 187 days post-vaccination in their sampled individuals [4]. Separate clinical series in patients with persistent post‑vaccine symptoms or post‑vaccine myocarditis have reported detection of spike protein in monocytes or free spike antigen in blood samples collected weeks-to-months after vaccination; one study of CD16+ monocytes in a symptomatic cohort sampled between 38–245 days reported S1 detection up to 245 days in some individuals [5]. A myocarditis series identified free spike antigen in adolescents and young adults sampled during January 2021–February 2022, indicating detectable spike in some affected patients in that timeframe [8] [9].
Context and caveats: these longer detections come from selective cohorts (symptomatic, biopsy or proteomic methods, or small case series), not from large population-based longitudinal sampling; methodological differences (assay type, target fragment, matrix—plasma vs monocytes vs tissue) matter greatly for whether and how long antigen is “detectable” [4] [5] [8].
4. Vaccine mRNA circulation and mechanisms that could prolong signal
RNA-seq and targeted assays have shown that vaccine mRNA sequences or fragments can circulate in plasma and be found up to ~28 days in some studies, likely protected inside lipid nanoparticles or within immune cells that traffic from the injection site, enabling continued local protein production and intermittent detectability [2] [10] [3]. Reviews note that LNP protection and lymphatic trafficking plausibly extend antigen production relative to initial expectations [2] [7].
Uncertainties: persistence of mRNA or spike in tissues does not by itself define functional consequences; available sources emphasize further research is needed to link persistent detection with clinical outcomes and to standardize assays [4] [7].
5. Competing viewpoints and methodological drivers of disagreement
Different studies reach different durations because they use different targets (S1 subunit, full-length spike, vaccine-unique recombinant fragments), matrices (plasma, monocytes, lymph node biopsies, cerebral arteries), and sensitivities (ultrasensitive immunoassays vs mass spectrometry vs RNA sequencing). Reviews and primary papers explicitly note that isolated long-detection reports often come from small or selected samples (symptomatic patients, biopsies) and should not be generalized without broader replication [4] [7] [5].
Implicit agendas: some papers emphasize safety implications and call for extended causality windows; others frame persistence as expected lymphoid retention that drives durable immunity. Readers should note whether a study samples symptomatic cohorts (which skew toward finding persistence) or general vaccinees (which more often show short clearance) [4] [5] [6].
6. Bottom line and what’s missing from current reporting
Available studies show spike or vaccine mRNA is commonly detectable in blood or plasma for days to a few weeks after mRNA vaccination, can persist in lymph nodes up to ~60 days, and has been detected at longer intervals (months, up to ~187–245 days in some reports) primarily in selective cohorts or with specialized assays [1] [3] [6] [4] [5]. Large, population-representative longitudinal studies using standardized assays are not reported in the provided set; available sources do not mention definitive prevalence rates of long-term detection in general populations nor clear causal links between persistence and clinical harm (not found in current reporting) [4] [5].
If you want, I can summarize which assays detect which spike fragments and map them to the studies above so you can judge methodological differences yourself [1] [4] [2] [6] [3] [5].