Search

Background Immune responses to each vaccine must be investigated to establish effective vaccination strategies for the ongoing coronavirus disease (COVID-19) pandemic. We investigated the long-term kinetics of immune responses after heterologous booster vaccination in relation to Omicron breakthrough infection (BI). Methods Our study included 373 healthcare workers who received primary ChAdOx1 vaccine doses and a third BNT162b2 vaccine dose. BIs that occurred after the third vaccine were investigated. Blood specimens were collected before and 3 months after the booster dose from participants without BI and 1, 4, and 6 months after BI from participants who experienced BI. Spike-specific binding and neutralizing antibody levels against the wild-type virus, Omicron BA.1, and Omicron BA.5, as well as cellular responses, were analyzed. Results A total of 346 participants (82 in the no BI group; 192 in the BI group during the BA.1/BA.2 period; 72 in the BI group during the BA.5 period) were included in the analysis. Participants without BI exhibited the highest binding and neutralizing antibody concentrations and greatest cellular response 1 month after the third vaccination, which reached a nadir by the ninth month. Antibody and cellular responses in participants who experienced BI substantially increased postinfection. Neutralizing antibody titers in individuals who experienced BI during the BA.1/BA.2 period showed more robust increase against wild-type virus than against BA.1 and BA.5. Conclusions Our findings provide evidence of antigenic imprinting in participants who received a heterologous booster vaccination, thereby serving as a foundation for further studies on the impact of BIs on immune responses. [ABSTRACT FROM AUTHOR]

Background SFTS and scrub typhus have similar clinical features and difficult to differentiate. Thus, a study to develop a scoring system to differentiate between two diseases in a clinical setting before the confirmation of laboratory results was reported by Kim et al. However, the statistical power could be low because of low numbers of cases (21 SFTS, 91 scrub typhus), our study analyzed by increasing the number of cases to overcome these limitations. Methods We retrospectively collected data from 183 SFTS and 178 scrub typhus patients who visited the 21 hospitals in South Korea between October, 2013 and November, 2017. The study protocol was approved by the IRB of each institution. SFTS was diagnosed through detection of SFTS viral RNA using RT–PCR. Scrub typhus was diagnosed either detection of 56-kDa antigen of O. tsutsugamushi using nested PCR or ≥ 4 fold rise in IgM or IgG titer using indirect IFA. Statistical analyses were performed by using SPSS and Medcalc. Results To differentiate SFTS from scrub typhus, we applied the scoring system proposed by Kim et al. After multivariable logistic regression, altered mental status, leukopenia, prolonged aPTT, and normal CRP(≤ 1.0 mg/dL) were significantly associated with SFTS compared with scrub typhus. Each variable was scored by 1 point, with a total score of 0–4 points, the optimal cutoff value was > 1 for the ROC curve. A score > 1 had 92% sensitivity, 96% specificity for diagnosis of SFTS, with a ROC AUC of 0.974. Because the sensitivity was less than 95%, we changed the normal CRP criteria to ≤ 3.0 mg/dL. The modified scoring system had 97% sensitivity, 96% specificity for diagnosis of SFTS, with an AUC of 0.983, and it showed a statistically higher accuracy than original scoring system (P = 0.0487). In this study, four factors for predicting SFTS were newly developed: leukopenia, prolonged aPTT, normal CRP (≤3.0 mg/dL), and elevated CK (>1,000 IU/L). Our study scoring system had 97% sensitivity, 98% specificity for diagnosis of SFTS, with an AUC of 0.992, and it showed a statistically higher accuracy than original scoring system (P = 0.0308). Conclusion In conclusion, we can easily differentiate SFTS from scrub typhus by using our scoring system of leukopenia, prolonged aPTT, normal CRP, and elevated CK in the endemic area. Disclosures All authors: No reported disclosures. [ABSTRACT FROM AUTHOR]