The clinical outcomes of high neutralizing antibodies titer convalescent plasma therapy in early developed severe COVID-19 patients; a case–control study

BACKGROUND: Coronavirus disease 2019 (COVID-19) causes life-threatening pneumonia. Convalescent plasma therapy (CPT) is expected to be the effective COVID-19 treatment for passive immunity. The high neutralizing antibodies titer of CPT is needed to prove the benefit in early developed severe COVID-19. OBJECTIVE: This case–control study evaluated transfusion efficacy and adverse events with high-titer (≥ 1:320) COVID-19 convalescent plasma compared with standard care alone in severe COVID-19 pneumonia. RESULTS: Among 107 severe COVID-19 patients, 55 received CPT plus standard care, and 52 received standard care alone. All-cause mortality was 15.3% in the CPT group compared with 85.4% in the standard care group (p < 0.001). Univariate and multivariate analyses revealed reduced mortality with CPT (HR 0.14; 95% CI 0.07–0.31; p < 0.001 and HR 0.26; 95% CI 0.08–0.79; p = 0.018, respectively). CPT resulted in decreased use of mechanical ventilation, duration of supplemental oxygen, and high-flow oxygen requirement. Clinical and radiological outcomes improved. CONCLUSIONS: Immediate high neutralizing antibody titer CPT is safe and reduces mortality in early developed severe COVID-19 patients. The benefit of CPT in the early course of illness is challenging and requires additional study. Trial registration Thai clinical trials registry (TCTR) no. 20220101003.