Haesook Seo

Introduction Following severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) infection, symptoms can persist for more than 12 weeks in over 10% of patients in a condition known as long coronavirus disease (COVID). Gut microbiota dysbiosis is correlated with long COVID, but the specific relationship between long COVID and the gut microbiome remains unclear. Here, we aimed to investigate connections between the gut microbiota and long COVID severity. Methods Fecal samples were collected from 31 patients with long COVID, 14 with COVID-19 but not long COVID, and 23 healthy controls. The mean interval between COVID-19 diagnosis and sample collection was 65.5 (range: 13.0–110.3) weeks for patients with long COVID and 74.8 (range: 50.7–110.4) weeks for positive control group. Gut microbiota composition was analyzed using 16S rRNA gene sequencing. Patient-reported outcomes were used to comprehensively assess long COVID symptom severity. Results Symptom severity was higher in patients with severe initial infections and significantly correlated with serum triglyceride, fasting blood glucose, and high-density lipoprotein-cholesterol levels. Results showed distinct microbial profiles in patients with long COVID. Leuconostoc, Actinomyces, and Granulicatella were significantly enriched, and they accurately distinguished patients with long COVID from controls, indicating their potential as long COVID biomarkers. Particular gut bacteria were significantly correlated with certain systemic, gastrointestinal, otolaryngologic, and visual symptoms. Parabacteroides, Eubacterium ventriosum group, and Rothia abundance was correlated with blood biomarkers that influence long COVID development, including total and low-density lipoprotein cholesterol and basophil levels. Conclusions The gut microbial signature of patients with long COVID differed from that of healthy controls. Certain microbial genera showed significant differences between patients with long COVID and controls, suggesting potential as preliminary biomarkers and therapeutic targets for long COVID pending validation in larger studies.

Background: Coronavirus disease 2019 (COVID-19) is a disease that is characterized by frequent reinfection. However, the factors influencing reinfection remain poorly elucidated, particularly regarding the effect of COVID-19 vaccination on preventing reinfection and its effects on symptomatology and the interval until reinfection. Methods: This retrospective cohort study examined patients with severe acute respiratory syndrome coronavirus reinfection between January 2020 and February 2022. This study included patients aged >17 years who were reinfected at least 90 days between two infections with severe acute respiratory syndrome coronavirus. The main outcome measure was a reduction in symptoms during reinfection, and reinfection interval. Results: Overall, 712 patients (average age: 40.52 ± 16.41 years; 312 males) were included. The reduction rate of symptoms at reinfection than that at first infection was significantly higher in the vaccinated group than in the unvaccinated group (p < 0.001). The average reinfection interval was 265.81 days. The interval between the first and second infection was 63.47 days longer in the vaccinated group than in the unvaccinated group. The interval was also 57.23 days, significantly longer in the asymptomatic group than in the symptomatic group (p < 0.001). Conclusions: Besides its role in preventing severe acute respiratory syndrome coronavirus infection, vaccination reduces the rate of symptomatic reinfection and increases the reinfection interval; thus, it is necessary to be vaccinated even after a previous infection. The findings may inform the decision to avail COVID-19 vaccination.

Background: We evaluated vaccine effectiveness (VE) against infections with SARS-CoV-2 variants of concern in Seoul, the capital of the Republic of Korea, having the highest population density in the country, under real-world conditions. Methods: We evaluated the reduction in the effectiveness of mRNA and viral-vector COVID-19 vaccines against infection by the SARS-CoV-2 delta variant in a subpopulation from April 2021 to July 2021 who visited screening clinics in Seoul using a test-negative case-control study design. Moreover, we conducted a case-control study matching the ten-year-old age group, sex, healthcare workers, and five districts of Seoul, which are considered confounding factors. Results: The full VE in the pre-delta-dominant period was 95.0% (95% confidence interval [CI]: 91.2–97.2); however, it decreased to 61.1% (95% CI: 53.2–67.6) during the delta-dominant period. Notably, we found that COVID-19 VE was significantly decreased in individuals aged ≥80 years (52.9%, 95% CI: −9.9–79.8), men (50.6 %, 95% CI: 39.4–59.8), and asymptomatic individuals (49.8%, 95% CI: 36.5–60.3) during the widespread SARS-CoV-2 delta variant circulation. Conclusions: Vaccine-mediated protection drastically declined during the delta-dominant period and in vulnerable groups. This study suggests the requirement for additional countermeasures, such as the administration of a booster vaccine, in vulnerable groups based on age, sex, and symptomatic manifestation.