Antibody titers and the risk of infection during the SARS-CoV-2 Omicron phase in Bizen City, Japan.

BACKGROUND: Understanding the association between the immune response and the risk of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection has implications for forthcoming prevention strategies. We evaluated the association between antibody titers and the risk of infection for the general population during the Omicron-dominant phase. METHODS: This was a prospective cohort study of residents or people affiliated with institutions in Bizen City, which included 1,899 participants. We measured the titers of antibodies against SARS-CoV-2 repeatedly every 2 months from June 2022 to March 2023. Infection status was obtained from self-reported questionnaires and the official registry. We estimated risk ratios (RRs) for infection within 2 months of the date of each antibody measurement with 95% confidence intervals (CIs) based on antibody titer categories and spline functions. RESULTS: Compared with the <2,500 arbitrary unit (AU)/mL category, the 2,500-5,000, 5,000-10,000, and ≥10,000 AU/mL categories had adjusted RRs (95% CI) of 0.81 (0.61-1.08), 0.51 (0.36-0.72), and 0.41 (0.31-0.54), respectively. The spline function showed a non-linear relationship between antibody titer and risk. CONCLUSIONS: Higher antibody titers were associated with a lower risk. We demonstrate the usefulness of measuring an antibody titers to determine the appropriate timing for future vaccination.

Zinc deficiency is a potential risk factor for COVID-19 progression to pneumonia requiring oxygen therapy.

INTRODUCTION: Various risk factors for developing severe coronavirus disease 2019 (COVID-19) have been reported. However, studies on the nutritional-related risk factors are limited. In this study, we investigated the effects of serum zinc deficiency on the severity of COVID-19. METHODS: The study included a total of 60 COVID-19 patients who were admitted to Tsuyama Chuo Hospital between March 2020 and April 2021. We divided the patients into two categories based on serum levels of zinc (normal and latent zinc deficiency vs. zinc deficiency [<60 µg/dL]) at the time of diagnosis. Severity of COVID-19 was defined as the most exaggerated disease status during admission. The associations between serum zinc deficiency and the severity of COVID-19 were examined using a logistic regression model adjusted for potential confounders. RESULTS: Patients who required oxygen therapy had a higher prevalence of comorbidities and poorer nutritional status, including zinc deficiency, than those who did not require oxygen therapy. Zinc deficiency was associated with an increased risk of COVID-19 severity, with an adjusted odds ratio of 7.29 (95% confidence interval: 1.70-31.18). This result remained significant in the sensitivity analyses conducted after adjusting for patient background factors. CONCLUSIONS: Zinc deficiency at the time of COVID-19 diagnosis is an independent risk factor for severe disease. Our findings need to be validated in external studies.

Significance of Continuous Low-Dose Lenvatinib for the Treating of the Patients with Unresectable Thyroid Carcinoma.

The tyrosine kinase inhibitor lenvatinib has been confirmed as an effective treatment option for patients with unresectable thyroid carcinoma. We conducted a retrospective analysis of the significance of the effect of continued lenvatinib treatment for the longest duration possible at a reasonable daily dose and with a minimum discontinuation period in 42 patients with unresectable thyroid carcinoma treated with lenvatinib between 2015 and 2020. A Cox proportional hazard model-based analysis revealed that the overall survival of the patients treated with a <8 mg/day mean dose of lenvatinib was significantly better than that of the patients treated with 8-24 mg/day (hazard ratio [HR] 0.38 for 1.14-4.54 mg/day, and HR 0.01 for 4.56-7.97 mg/day) adjusted for various factors (e.g., sex, age, drug interruption period). The cumulative dose of lenvatinib administered tended to be higher in the patients treated with low doses (< 8 mg/day) than in the patients treated with relatively high doses (8-24 mg/day). Considering its adverse events, the continuation of lenvatinib treatment with an adequate daily dose and drug interruption may help prolong the survival of patients with unresectable thyroid carcinoma.

Longitudinal antibody dynamics after COVID-19 vaccine boosters based on prior infection status and booster doses.

Global concern over COVID-19 vaccine distribution disparities highlights the need for strategic booster shots. We explored longitudinal antibody responses post-booster during the Omicron wave in a Japanese cohort, emphasizing prior infection and booster doses. This prospective cohort study included 1763 participants aged 18 years and older with at least three vaccine doses (7376 datapoints). Antibody levels were measured every 2 months. We modeled temporal declines in antibody levels after COVID-19 vaccine boosters according to prior infection status and booster doses using a Bayesian linear mixed-effects interval-censored model, considering age, sex, underlying conditions, and lifestyle. Prior infection enhanced post-booster immunity (posterior median 0.346, 95% credible interval [CrI] 0.335-0.355), maintaining antibody levels (posterior median 0.021; 95% CrI 0.019-0.023) over 1 year, in contrast to uninfected individuals whose levels had waned by 8 months post-vaccination. Each additional booster was correlated with higher baseline antibody levels and slower declines, comparing after the third dose. Female sex, older age, immunosuppressive status, and smoking history were associated with lower baseline post-vaccination antibodies, but not associated with decline rates except for older age in the main model. Prior infection status and tailored, efficient, personalized booster strategies are crucial, considering sex, age, health conditions, and lifestyle.

Longitudinal changes in antibody titers in a nursing home in which COVID-19 clusters occurred.

BACKGROUND: Many outbreaks of coronavirus disease 2019 have occurred in Japanese nursing homes in which residents and staff are in close daily contact. This study evaluated longitudinal changes in antibody titers in nursing homes in which clusters occurred and examined the association between antibody titer and the severe acute respiratory syndrome coronavirus 2 infection or severity. METHODS: This cohort study included 171 participants who had provided at least one antibody titer test between June 2022 and March 2023. A descriptive analysis estimated the association between the risk of infection and antibody titer level. RESULTS: The facility experienced 2 clusters during the study period that involved facility staff as the initial source of infection. Noninfected participants had less variation in antibody titer levels and a higher level of preinfection antibodies than infected participants. The risk of infection and severity was lower in participants with higher antibody titers than in those with lower titers. CONCLUSIONS: We showed the changes in antibody titers over time and the association between antibody titer and severe acute respiratory syndrome coronavirus 2 infection or severity. Vaccination schedules may need to be tailored to the dynamics of decreasing antibody titers over time and the occurrence of infectious diseases in facilities.

Kinetics of SARS-CoV-2 antibody titers after booster vaccinations during an Omicron surge in Japan.

BACKGROUND: Despite the emergence of SARS-CoV-2 variants and waning immunity after initial vaccination, data on antibody kinetics following booster doses, particularly those adapted to Omicron subvariants like XBB.1.5, remain limited. This study assesses the kinetics of anti-spike protein receptor-binding domain (S-RBD) IgG antibody titers post-booster vaccination in a Japanese population during the Omicron variant epidemic. METHODS: A prospective cohort study was conducted in Bizen City, Japan, from November 2023 to January 2024. Participants included residents and workers aged ≥18 years, with at least three COVID-19 vaccinations. Antibody levels were measured from venous blood samples. The study analyzed 424 participants and 821 antibody measurements, adjusting for variables such as age, sex, underlying conditions, and prior infection status. Mixed-effects models were employed to describe the kinetics of log-transformed S-RBD antibody titers. RESULTS: The study found that S-RBD antibody titers declined over time but increased with the number of booster vaccinations, particularly those adapted to Omicron and its subvariant XBB.1.5 (Pfizer-BioNTech Omicron-compatible: 0.156, 95%CI -0.032 to 0.344; Pfizer-BioNTech XBB-compatible: 0.226; 95%CI -0.051 to 0.504; Moderna Omicron-compatible: 0.279, 95%CI 0.012 to 0.546; and Moderna XBB-compatible: 0.338, 95%CI -0.052 to 0.728). Previously infected individuals maintained higher antibody titers, which declined more gradually compared to uninfected individuals (coefficient for interaction with time 0.006; 95%CI 0.001 to 0.011). Sensitivity analyses using Generalized Estimating Equations and interval-censored random intercept model confirmed the robustness of these findings. CONCLUSIONS: The study provides specific data on antibody kinetics post-booster vaccination, including the XBB.1.5-adapted vaccine, in a highly vaccinated Japanese population. The results highlight the importance of considering individual demographics and prior infection history in optimizing vaccination strategies.