The specific antibodies induced by SARS-CoV-2 infection may provide protection against a subsequent infection. However, the efficacy and duration of protection provided by naturally acquired immunity against subsequent SARS-CoV-2 infection remain controversial. We systematically searched for the literature describing COVID-19 reinfection published before 07 February 2022. The outcomes were the pooled incidence rate ratio (IRR) for estimating the risk of subsequent infection. The Newcastle–Ottawa Scale (NOS) was used to assess the quality of the included studies. Statistical analyses were conducted using the R programming language 4.0.2. We identified 19 eligible studies including more than 3.5 million individuals without the history of COVID-19 vaccination. The efficacy of naturally acquired antibodies against reinfection was estimated at 84% (pooled IRR = 0.16, 95% CI: 0.14-0.18), with higher efficacy against symptomatic COVID-19 cases (pooled IRR = 0.09, 95% CI = 0.07-0.12) than asymptomatic infection (pooled IRR = 0.28, 95% CI = 0.14-0.54). In the subgroup analyses, the pooled IRRs of COVID-19 infection in health care workers (HCWs) and the general population were 0.22 (95% CI = 0.16-0.31) and 0.14 (95% CI = 0.12-0.17), respectively, with a significant difference (
P
= 0.02), and those in older (over 60 years) and younger (under 60 years) populations were 0.26 (95% CI = 0.15–0.48) and 0.16 (95% CI = 0.14-0.19), respectively. The risk of subsequent infection in the seropositive population appeared to increase slowly over time. In conclusion, naturally acquired antibodies against SARS-CoV-2 can significantly reduce the risk of subsequent infection, with a protection efficacy of 84%.
Registration number:
CRD42021286222
In individuals with underlying chronic liver disease (CLD), hepatitis E virus (HEV) infection is a potential trigger of acute‐on‐chronic liver failure. In this systematic review, seven electronic databases were searched. Pooled incidence rates with 95% confidence intervals (95% CIs) were calculated by the Freeman–Tukey double arcsine transformation method. The association between death or liver failure and HEV superinfection in CLD patients was estimated by the odds ratios (OR) with a 95% CI. A total of 18 studies from 5 countries were eligible for systematic review. The prevalence of acute HEV infection in hospitalized CLD patients with clinical manifestations of hepatitis was 13.6%, which was significantly higher than that in CLD patients from the community (pooled prevalence 1.1%). The overall rates of liver failure and mortality in CLD patients with HEV superinfection were 35.8% (95% CI: 26.7%–45.6%) and 14.3% (95% CI: 10.6%–18.5%), respectively, with the rates in cirrhotic patients being approximately 2‐fold and 4‐fold higher than those in noncirrhotic patients, respectively. The risks of liver failure (OR = 5.5, 95% CI: 1.5–20.1) and mortality (OR = 5.0, 95% CI: 1.9–13.3) were significantly higher in CLD patients with HEV superinfection than in those without HEV superinfection. HEV testing in hospitalized CLD patients is necessary due to the high prevalence of HEV infection observed in hospitalized CLD patients. HEV superinfection could accelerate disease progression in patients with underlying CLD and increase mortality in these patients. HEV vaccination is appropriate for patients with pre‐existing CLD.
The live-attenuated influenza virus vector-based intranasal vaccine (dNS1-RBD, Pneucolin®) is the world’s first COVID-19 mucosal vaccine to enter human trials, and has been issued for emergency use authorization in China. Here, we report safety and efficacy data from a multi-centre randomized, double-blind, placebo-controlled phase 3 clinical trial of Pneucolin® (two doses, 14 days apart) in adults (18 years and older) during the Omicron circulation. The result showed a favorable safety profile, with no difference in the incidence of adverse reactions between the vaccine and placebo groups. In the per-protocol set, for symptomatic COVID-19, the efficacies among total population, naïve participants, particiants with inactivated vacciantion history were 32.6% (95%CI 8.2 to 50.5), 55.2% (95%CI 13.8 to 76.7), 38.2% (95%CI -49.2 to 74.4) , and for symptomatic COVID-19 with three or more of the suspected symptoms, the efficacies were 42.3% (95%CI 15.7 to 60.5), 66.7% (95%CI 8.3 to 87.9) and 63.1% (95%CI -15.8 to 88.3) for the above mentioned 3 cohorts. An efficacy of 100.0% (95%CI -9.2 to 100.0) against hospitalized COVID-19 was observed in the whole enrolled population. We conclude that Pneucolin® is well-tolerated and can be an antibody-independent broad-spectrum effective tool to combat SARS-CoV-2 variants, as primary immunization or heterologous booster.
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