Immune response after SARS-CoV-2 infection with residual post COVID symptoms (preprint)

BACKGROUND In a number of patients, post-acute COVID syndrome develops after acute infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) (Long COVID [LC]). Here, we examined the immune responses and clinical characteristics of individuals with LC compared to age- and gender-matched healthy recovered COVID individuals (HC) during the Omicron pandemic. Immune responses following BNT162b2 (Pfizer) booster are also determined. METHODS This retrospective cohort study included 292 patients (LC, 158; HC, 134) confirmed to have SARS-CoV-2 infection from January to August 2022. We determined anti-SARS-CoV-2 receptor-binding domain immunoglobulin G (anti-RBD IgG), surrogate virus neutralization test (sVNT), T-cell subsets, and neutralization of wild-type, BA.1 and BA.5. A subset of patients was voluntarily recruited for booster vaccination with BNT162b2 vaccine and immunogenicity was assessed 4weeks after vaccination. RESULTS Cycle thresholds were higher in the HC group than in the LC group (20.7 vs. 19.7; P<0.039). Anti-RBD IgG was higher at [≤]56 days after COVID-19 onset (PC) in 3-dose vaccines compared with 2-dose vaccines in the LC group (P=0.02) and after 57-84 days PC in 3-dose vaccines in the HC group (P<0.001). The sVNT in LC was significantly high against Wuhan and sVNT was 30% lower against the Omicron than the Wuhan. sVNT was relatively sustained in 3-dose vaccines than [≤] 2-dose vaccines. sVNT in the HC group reached its peak at 57-84 days PC as compared with the LC group. CONCLUSIONS These findings imply that LC produced increased neutralizing antibody responses than those with HC. During the Omicron pandemic, immunity after LC has still waned; therefore, a booster vaccine may be needed after 2-3 months from last infection. (ClinicalTrials.gov number, NCT05484700)

Immunity response against mild-to-moderate breakthrough COVID-19 (preprint)

BACKGROUND The Omicron variant prevails the Delta variant after December 2021 in Thailand. Both variants of concern embody diverse epidemiological trends and immunogenicity, raising enormous public health concerns. We determined whether biological and clinical characteristics and immunogenicity of patients differ between Delta and Omicron during post-coronavirus disease 2019 (COVID-19) stage. METHODS A retrospective cohort study involved patients with mild-to-moderate COVID-19 who were under a home isolation (HI) strategy. Clinical outcomes and laboratory data of 2704 and 2477 patients during the Delta and Omicron pandemics were analyzed, respectively. We evaluated anti-receptor binding domain immunoglobulin G (anti-RBD IgG) and surrogate viral neutralizing (sVNT) activity in a subset of 495 individuals post-COVID-19 infection during the Delta pandemic. RESULTS Eighty-four percent of all patients received antiviral treatment. The peak cycle threshold (Ct) values, which inversely related to viral load, were lower in the Omicron (19 [IQR=17-22]) compared with the Delta (21 [IQR=18- 26]; p<0.001), regardless of vaccination status. Upper respiratory tract symptoms were common signs during the Omicron compared with the Delta pandemic. At least two-dose vaccination reduced the chance of hospital readmissions by 10-30% and death by less than 1%. Furthermore, anti-RBD IgG and sVNT against the Delta variants tended to be higher among the older individuals after post-COVID 19 infections and expressed in the long interval after two-dose vaccination than in other groups. CONCLUSIONS Mild-to-moderate Delta and Omicron breakthrough infection with prior full vaccination is limitedly immunogenic; thereby exerting reduced protection against reinfection and infection from novel variants. However, this may be only sufficient to prevent hospitalization and death, particularly in countries where vaccines are limited. (ClinicalTrials.gov number, NCT05328479.)