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How Long Does Spike Protein Stay in the Body?

Last updated: October 26, 2026

Short answer

Most studies find that vaccine-derived spike protein is cleared from the blood within days to weeks. After infection, most people also clear it, but some studies detect spike for months in a minority of people, more often in those with Long COVID. A few studies of people with persistent symptoms after vaccination report detection for months or longer; those findings are preliminary and have not been replicated.

After vaccination

The most direct measurement comes from Ogata et al. (2022), who tracked 13 people after the Moderna mRNA-1273 vaccine using an ultra-sensitive (Simoa) assay. Spike protein or its S1 subunit appeared in the blood of 11 of 13 participants from day one, then became undetectable within about two weeks as antibodies rose. It was not detected after the second dose.

Two findings point to longer local persistence. Röltgen et al. (2022) found vaccine mRNA and spike antigen in lymph-node germinal centres, where immune responses are built, up to 8 weeks after vaccination in some cases. Yonker et al. (2023) detected free circulating spike in young people who developed myocarditis after mRNA vaccination, but not in vaccinated controls; those samples were taken within weeks of vaccination, not months.

After infection

Infection exposes the body to far more viral protein than a vaccine dose, and most people clear it during recovery. Swank et al. (2023) detected circulating spike mainly in people with Long COVID, up to 12 months after diagnosis. Peluso et al. (2024) measured viral antigens in the UCSF LIINC cohort and found them in a minority of people up to about 14 months after infection, more often in those who had been hospitalised or had more Long COVID symptoms.

Spike protein and Long COVID →

Reports of longer detection after vaccination

A small number of studies report spike in people with chronic symptoms after vaccination, sometimes called post-vaccination syndrome. The Yale LISTEN preprint (Bhattacharjee et al., 2025) found higher circulating spike in 42 people with post-vaccination syndrome than in 22 controls. Patterson et al. (2025) reported S1 protein inside CD16+ monocytes up to 245 days after vaccination in 50 symptomatic people; several authors work for the company that makes the test. A 2026 systematic review collected these and other outlier reports.

These are preliminary findings. The groups were small and chosen because they were ill, and infection cannot be fully ruled out as the source of the spike. None has yet been independently replicated.

Spike protein and post-vaccination syndrome →

Why studies disagree

  • Assay sensitivity.Simoa assays detect sub-pg/mL amounts that standard ELISA kits miss, so “not detected” depends on the test used.
  • Who is sampled. Studies of symptomatic patients will find more positives than studies of the general vaccinated population.
  • Source of the spike. Most assays cannot tell vaccine-encoded spike from spike made during an unnoticed infection.
  • Detection is not harm. Finding spike shows it is present, not that it causes symptoms.

Go deeper

References