Dynamic SARS-CoV-2-specific B-cell and T-cell responses following immunization with an inactivated COVID-19 vaccine.

OBJECTIVE: The dynamic adaptive immune responses elicited by the inactivated virus vaccine CoronaVac remain elusive. METHODS: In a prospective cohort of 100 healthcare professionals naïve for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) who received two doses of CoronaVac, we analysed SARS-CoV-2-specific humoral and cellular responses at four different timepoints, including before vaccination (T1), 2 weeks after the first dose (T2), 2 weeks after the booster dose (T3), and 8-10 weeks after the booster dose (T4). SARS-CoV-2-specific antibodies, serum neutralizing activities, peripheral B cells, CD4+ and CD8+ T cells and their memory subsets were simultaneously measured in this cohort. RESULTS: SARS-CoV-2 spike-specific IgG responses reached a peak (geometric mean titre (GMT) 54827, 30969-97065) after two doses and rapidly declined (GMT 502, 212-1190) at T4, whereas suboptimal IgA responses were detected (GMT 5, 2-9). Spike-specific circulating B cells (0.60%, 0.46-0.73% of total B cells) and memory B cells (1.18%, 0.92-1.44% of total memory B cells) were effectively induced at T3 and sustained over time (0.33%, 0.23-0.43%; 0.87%, 0.05-1.67%, respectively). SARS-CoV-2-specific circulating CD4+ T cells (0.57%, 0.47-0.66%) and CD8+ T cells (1.29%, 1.04-1.54%) were detected at T3. At T4, 0.78% (0.43-1.20%) of memory CD4+ T cells and 0.68% (0.29-1.30%) of memory CD8+ T cells were identified as SARS-CoV-2-specific, while 0.62% (0.51-0.75%) of CD4+ T cells and 0.47% (0.38-0.58%) of CD8+ T cells were SARS-CoV-2-specific terminally differentiated effector memory cells. Furthermore, age and interval between doses affected the magnitude of CoronaVac-induced immune responses. SARS-CoV-2 memory CD4+ T cells were strongly associated with both receptor binding domain (RBD)-specific memory B cells (r 0.87, p <0.0001) and SARS-CoV-2-specific memory CD8+ T cells (r 0.48, p <0.0001). CONCLUSIONS: CoronaVac induced robust circulating and memory B cell and T cell responses. Our study offers new insight into the underlying immunobiology of inactivated virus vaccines in humans and may have implications for vaccine strategies in the future.

Surveillance of SARS-CoV-2 infection among frontline health care workers in Wuhan during COVID-19 outbreak.

INTRODUCTION: As an emerging infectious disease, coronavirus disease 2019 (COVID-19) has rapidly spread throughout worldwide. Health care workers (HCWs) on frontline directly participated in the diagnosis, treatment, and care of COVID-19 patients are at high risk of getting infected with the highly infectious severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the novel coronavirus that causes COVID-19. In Nanjing Drum Tower Hospital, a total of 222 medical staff went to Wuhan city for support. In this study, we aimed to determine any nosocomial infection among our cohort of HCWs who worked in Wuhan. METHODS: Throat swab samples were obtained for RNA testing on day 1 and 14 of their quarantine upon their return to Nanjing. Radiological assessments were performed by chest computed tomography (CT) on day 14 of their quarantine. The blood was collected from 191 HCWs between May 12 and May 15. Anti-SARS-CoV-2 immunoglobulin M (IgM) and IgG antibody responses were determined by a chemiluminescence immunoassay. RESULTS: All the throat swab specimens were found negative for SARS-CoV-2. The radiological analysis revealed that there was no typical chest CT scan of COVID-19 among 222 HCWs. Consistently, anti-SARS-CoV-2 IgM or IgG was also found to be negative among 191 HCWs. CONCLUSIONS: There was no nosocomial infection of SARS-CoV-2 among our cohort of the frontline HCWs, suggesting that zero occupational infection is an achievable goal with appropriate training, strict compliance, and psychological support for the frontline HCWs.

Corticosteroid treatment in severe COVID-19 pneumonia: two cases and literature review.

Coronavirus disease 2019 (COVID-19) pneumonia, firstly reported in Wuhan, Hubei province, China, has rapidly spread around the world with high mortality rate among critically ill patients. The use of corticosteroids in COVID-19 remains a major controversy. Available evidences are inconclusive. According to WHO guidance, corticosteroids are not recommended to be used unless for another reason. Chinese Thoracic Society (CTS) proposes an expert consensus statement that suggests taking a prudent attitude of corticosteroid usage. In our clinical practice, we do not use corticosteroids routinely; only low-to-moderate doses of corticosteroids were given to several severely ill patients prudently. In this paper, we will present two confirmed severe COVID-19 cases admitted to isolation wards in Optical Valley Campus of Tongji hospital, Tongji Medical College, Huazhong University of Science and Technology. We will discuss questions related to corticosteroids usages.