Japanese journal of infectious diseasesAug 3, 2026

Long COVID symptoms over time linked to COVID-19 vaccination status

Updated Aug 4, 2026

Abstract

A total of 59 patients were evaluated for long COVID symptom trajectories based on post-COVID-19 vaccination status.

The most frequently reported symptoms included memory problems, fatigue, brain fog, word-finding difficulties, and excessive sweating.
Symptom scores decreased significantly over time across the overall patient cohort.
No statistically significant association was found between vaccination status and the trajectory of symptoms.
Vaccinated participants showed higher SARS-CoV-2 IgG antibody levels, but these levels were not linked to symptom burden.
The study's findings are limited by a small sample size and substantial group imbalance, indicating the need for caution in interpretation.

Simplified

Long COVID remains a substantial public health challenge, and the relationship between post-COVID-19 vaccination and symptom persistence remains uncertain. This prospective longitudinal study evaluated long COVID symptom trajectories according to post-COVID-19 vaccination status. Adult patients who were unvaccinated at the time of COVID-19 diagnosis were followed at 1, 3, 6, and 9 months and categorized according to vaccination status. Symptom Tool (ST) and Impact Tool (IT) scores and SARS-CoV-2 IgG antibody levels were assessed longitudinally. A total of 59 patients (mean age 43.1±14.1 years; 45.8% male) were included, of whom eight were vaccinated. The most frequently reported symptoms were memory problems, fatigue, brain fog, word-finding difficulties, and excessive sweating. Baseline characteristics were broadly comparable between groups. ST and IT scores decreased significantly over time in the overall cohort; however, no statistically significant association between vaccination status and symptom trajectories was identified. SARS-CoV-2 IgG antibody levels were higher among vaccinated participants but were not associated with symptom burden. Given the small sample size and substantial group imbalance, the study is underpowered and the findings should be interpreted cautiously. Larger prospective studies are needed to better clarify the relationship between post-COVID-19 vaccination and long COVID outcomes.

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Long COVID symptoms over time linked to COVID-19 vaccination status

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