Observation of changes of early laboratory indicators and COVID-19 vaccine protection in patients infected with SARS-CoV-2 Delta variant

Objective: To observe early laboratory indicators in peripheral blood of patients infected with SARSCoV- 2 Delta variant and the protective effects of COVID-19 vaccine on patients infected with SARS-CoV-2 Delta variant, in order to provide reference for epidemic prevention and control. Methods: Twenty-five Chengdu local confirmed nonsevere COVID-19 patients over 18 years old who were infected with COVID-19 caused by Delta variant in November 2021 were included as the research group, 22 cases of whom were vaccinated with COVID-19 vaccine before infection, and 3(2 cases over 80 years old)were unvaccinated. In addition, 71 non-severe COVID-19 patients at the age of over 18 years diagnosed in Chengdu from January 2020 to February 2020 were included as the control group. Peripheral blood was collected for laboratory examination in all cases on the first or second days after admission, and peripheral blood was collected for laboratory examination again in patients on day 4 to 8 after admission in the research group. Laboratory indicators included the blood routine, C-reactive protein, procalcitonin, liver function, myocardial enzyme profile, coagulation routine, T lymphocyte subsets, SARS-CoV-2 IgG antibody, and total antibody, etc. The first peripheral blood laboratory test results: of the two groups were compared to observe the protective effect of COVID-19 vaccine on patients infected with SARS-CoV- 2 Delta variant. Results Among the first time of laboratory indicators after admission, the lymphocyte count, lactate dehydrogenase, and D-dimer in the research group were all lower than those in the control group(all P < 0.05), and the procalcitonin and aspartate aminotransferase were higher than those in the control group(all P < 0.05). Among the 22 cases who had gotten vaccine before infection in the research group, there were 5 cases with positive result of SARS-CoV-2 IgG antibody in the first time of peripheral blood, 22 cases with positive result of SARS-CoV-2 IgG antibody in the second time of peripheral blood, and none of them became severe cases. During 3 unvaccinated cases, twice of the SARS-CoV-2 IgG antibody were both negative among the 2 cases over 80 years who had not vaccinated in the research group, then they became severe cases on day 6-8 during hospitalization, and the rest one had negative result of SARS-CoV-2 IgG antibody in the second time of peripheral blood. Among the 22 vaccinated cases in the research group, the lymphocyte count, CD4+T cell count, CD8+T cell count, SARS-CoV-2 specific antibodies in the second time peripheral blood were all higher than those in the first time of peripheral blood(all P < 0.05), and platelet count, hemoglobin, total protein, creatine kinase were all lower than those in the first time of peripheral blood(all P < 0.05). Conclusions: Lymphocyte count at early admission in COVID-19 patients infected with Delta variant may be lower than that infected with wild strain. COVID-19 vaccine can reduce the risk of infection of SARS-CoV-2 Delta variant by preventing the emergence of inflammatory storms and producing a large number of specific antibodies.

Epidemiological characteristics and quarantine assessment of imported international COVID-19 cases, March to December 2020, Chengdu, China.

International flights have accelerated the global spread of Coronavirus Disease 2019 (COVID-19). Determination of the optimal quarantine period for international travelers is crucial to prevent the local spread caused by imported COVID-19 cases. We performed a retrospective epidemiological study using 491 imported COVID-19 cases in Chengdu, China, to describe the characteristic of the cases and estimate the time from arrival to confirmation for international travelers using nonparametric survival methods. Among the 491 imported COVID-19 cases, 194 (39.5%) were asymptomatic infections. The mean age was 35.6 years (SD = 12.1 years) and 83.3% were men. The majority (74.1%) were screened positive for SARS-CoV-2, conducted by Chengdu Customs District, the People's Republic of China. Asymptomatic cases were younger than presymptomatic or symptomatic cases (P < 0.01). The daily number of imported COVID-19 cases displayed jagged changes. 95% of COVID-19 cases were confirmed by PT-PCR within 14 days (95% CI 13-15) after arriving in Chengdu. A 14-day quarantine measure can ensure non-infection among international travelers with a 95% probability. Policymakers may consider an extension of the quarantine period to minimize the negative consequences of the COVID-19 confinement and prevent the international spread of COVID-19. Nevertheless, the government should consider the balance between COVID-19 and socioeconomic development, which may cause more serious social and health crises.

Humoral responses after inactivated COVID-19 vaccination in individuals with and without prior SARS-CoV-2 infection: A prospective cohort study.

We evaluated and compared humoral immune responses after inactivated coronavirus disease 2019 (COVID-19) vaccination among naïve individuals, asymptomatically infected individuals, and recovered patients with varying severity. In this multicenter, prospective cohort study, blood samples from 666 participants were collected before and after 2 doses of inactivated COVID-19 vaccination. Among 392 severe acute respiratory syndrome coronavirus 2-naïve individuals, the seroconversion rate increased significantly from 51.8% (median antispike protein pan-immunoglobulins [S-Igs] titer: 0.8 U/ml) after the first dose to 96% (median S-Igs titer: 79.5 U/ml) after the second dose. Thirty-two percent of naïve individuals had detectable neutralizing antibodies (NAbs) against the original strain but all of them lost neutralizing activity against the Omicron variant. In 274 individuals with natural infection, humoral immunity was significantly improved after a single vaccine dose, with median S-Igs titers of 596.7, 1176, 1086.5, and 1828 U/ml for asymptomatic infections, mild cases, moderate cases, and severe/critical cases, respectively. NAb titers also improved significantly. However, the second dose did not substantially increase antibody levels. Although a booster dose is needed for those without infection, our findings indicate that recovered patients should receive only a single dose of the vaccine, regardless of the clinical severity, until there is sufficient evidence to confirm the benefits of a second dose.

Analysis of the close contact management mode and epidemiological characteristics of COVID-19 in Chengdu, China.

With the development of the novel coronavirus disease 2019 (COVID-19) epidemic and the increase in cases, as a potential source of infection, the risk of close contact has gradually increased. However, few studies have analyzed the tracking and management of cross-regional personnel. In this study, we hope to understand the effectiveness and feasibility of existing close contact management measures in Chengdu, so as to provide a reference for further prevention and control of the epidemic. The close contact management mode and epidemiological characteristics of 40,425 close contacts from January 22, 2020, to March 1, 2022, in Chengdu, China, were analyzed. The relationship with index cases was mainly co-passengers (57.58%) and relatives (7.20%), and the frequency of contact was mainly occasional contact (70.39%). A total of 400 (0.99%) close contacts were converted into cases, which were mainly found in the first and second nucleic acid tests (53.69%), and the contact mode was mainly by sharing transportation (63.82%). In terms of close contact management time, both the supposed ((11.93 ± 3.00) days vs. (11.92 ± 7.24) days) and actual ((13.74 ± 17.47) days vs. (12.60 ± 4.35) days) isolation times in Chengdu were longer than those of the outer cities (P < 0.001). For the local clustered epidemics in Chengdu, the relationship with indexed cases was mainly colleagues (12.70%). The tracing and management of close contacts is a two-way management measure that requires cooperation among departments. Enhancing existing monitoring and response capabilities can control the spread of the epidemic to a certain extent.

SARS-CoV-2 specific antibody levels after a third dose of inactivated vaccine among 91 medical staff in Chengdu

Objective: To analysis the production of SARS-CoV-2 antibody among medical staff in Public Health Clinical Center of Chengdu 1 month after a third dose of inactivated vaccine (booster shot), and to compare the SARS-CoV-2 antibody among COVID-19 patients after immunization, in order to analyze the effect of the booster shot.

Epidemiological characteristics of imported cases of coronavirus disease 2019 in Chengdu, Sichuan

Objective: To understand the epidemiological characteristics of imported coronavirus disease 2019 (COVID-19) cases detected in Chengdu, Sichuan, and provide scientific basis for the prevention and control of COVID-19.