ABSTRACT
Multiple severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) exposures, from infection or vaccination, can potently boost spike antibody responses. Less is known about the impact of repeated exposures on T cell responses. Here, we compare the prevalence and frequency of peripheral SARS-CoV-2-specific T cell and immunoglobulin G (IgG) responses in 190 individuals with complex SARS-CoV-2 exposure histories. As expected, an increasing number of SARS-CoV-2 spike exposures significantly enhances the magnitude of IgG responses, while repeated exposures improve the number of T cell responders but have less impact on SARS-CoV-2 spike-specific T cell frequencies in the circulation. Moreover, we find that the number and nature of exposures (rather than the order of infection and vaccination) shape the spike immune response, with spike-specific CD4 T cells displaying a greater polyfunctional potential following hybrid immunity compared with vaccination only. Characterizing adaptive immunity from an evolving viral and immunological landscape may inform vaccine strategies to elicit optimal immunity as the pandemic progress.
Subject(s)
COVID-19 , Immunoglobulin G , T-Lymphocytes , Humans , Antibody Formation , CD4-Positive T-Lymphocytes , COVID-19/epidemiology , SARS-CoV-2ABSTRACT
Background: Randomized controlled trials (RCTs) have reported inconsistent effects from intensified anticoagulation on clinical outcomes in coronavirus disease 2019 (COVID-19). We performed an aggregate data meta-analysis from available trials to quantify effect on nonfatal and fatal outcomes and identify subgroups who may benefit. Methods: We searched multiple databases for RCTs comparing intensified (intermediate or therapeutic dose) vs prophylactic anticoagulation in adults with laboratory-confirmed COVID-19 through 19 January 2022. We used random-effects meta-analysis to estimate pooled risk ratios for mortality, thrombotic, and bleeding events (at end of follow-up or discharge) and performed subgroup analysis for clinical setting and dose of intensified anticoagulation. Results: Eleven RCTs were included (N = 5873). Intensified vs prophylactic anticoagulation was not associated with a mortality reduction up to 45 days (risk ratio [RR], 0.93 [95% confidence interval {CI}, .79-1.10]). There was a possible signal of mortality reduction for non-intensive care unit (ICU) patients, although with low precision and high heterogeneity (5 studies; RR, 0.84 [95% CI, .49-1.44]; I 2 = 75%). Risk of venous thromboembolism was reduced (RR, 0.53 [95% CI, .41-.69]; I 2 = 0%), with effect driven by therapeutic rather than intermediate dosing (interaction P = .04). Major bleeding was increased with intensified anticoagulation (RR, 1.73 [95% CI, 1.17-2.56]) with no interaction for dosing and clinical setting. Conclusions: Intensified anticoagulation has no effect on mortality among hospitalized adults with COVID-19 and is associated with increased bleeding risk. The observed reduction in venous thromboembolism risk and trend toward reduced mortality in non-ICU settings requires exploration in additional RCTs. Clinical Trials Registration. CRD42021273449 (PROSPERO).
ABSTRACT
Objectives Randomised controlled trials (RCTs) have reported inconsistent effects from intensified anticoagulation on clinical outcomes in Covid-19. We performed an aggregate data meta-analysis from available trials to quantify effect on non-fatal and fatal outcomes and identify subgroups who may benefit. Methods We searched multiple databases for RCTs comparing intensified (intermediate or therapeutic dose) versus prophylactic anticoagulation in adults with laboratory-confirmed Covid-19 through 19 January 2022. We used random effects meta-analysis to estimate pooled risk ratios for mortality, thrombotic, and bleeding events (at end of follow-up or discharge) and performed subgroup analysis for clinical setting and dose of intensified anticoagulation. Results Eleven RCTs were included (n = 5873). Intensified versus prophylactic anticoagulation was not associated with a mortality reduction up to 45 days (relative risk (RR) 0.93;95%CI 0.79–1.10). There was a possible signal of mortality reduction for non-ICU patients, although with low precision and high heterogeneity (5 studies;RR 0.84;95% CI 0.49 - 1.44;I2 = 75%). Risk of venous thromboembolism was reduced (RR 0.53, 95%CI 0.41–0.69;I2 = 0%), with effect driven by therapeutic rather than intermediate dosing (interaction P = 0.04). Major bleeding was increased with intensified anticoagulation (RR 1.73, 95%CI 1.17–2.56) with no interaction for dosing and clinical setting. Conclusion Intensified anticoagulation has no effect on mortality among hospitalised adults with Covid-19 and is associated with increased bleeding risk. The observed reduction in venous thromboembolism risk and trend towards reduced mortality in non-ICU settings requires exploration in additional RCTs.
ABSTRACT
The SARS-CoV-2 Omicron variant (B.1.1.529) has multiple spike protein mutations1,2 that contribute to viral escape from antibody neutralization3-6 and reduce vaccine protection from infection7,8. The extent to which other components of the adaptive response such as T cells may still target Omicron and contribute to protection from severe outcomes is unknown. Here we assessed the ability of T cells to react to Omicron spike protein in participants who were vaccinated with Ad26.CoV2.S or BNT162b2, or unvaccinated convalescent COVID-19 patients (n = 70). Between 70% and 80% of the CD4+ and CD8+ T cell response to spike was maintained across study groups. Moreover, the magnitude of Omicron cross-reactive T cells was similar for Beta (B.1.351) and Delta (B.1.617.2) variants, despite Omicron harbouring considerably more mutations. In patients who were hospitalized with Omicron infections (n = 19), there were comparable T cell responses to ancestral spike, nucleocapsid and membrane proteins to those in patients hospitalized in previous waves dominated by the ancestral, Beta or Delta variants (n = 49). Thus, despite extensive mutations and reduced susceptibility to neutralizing antibodies of Omicron, the majority of T cell responses induced by vaccination or infection cross-recognize the variant. It remains to be determined whether well-preserved T cell immunity to Omicron contributes to protection from severe COVID-19 and is linked to early clinical observations from South Africa and elsewhere9-12.