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Vaccine-induced neutralizing antibodies are key in combating the COVID-19 pandemic. However, delays of boost immunization due to limited availability of vaccines may leave individuals vulnerable to infection and disease for prolonged periods. The emergence of SARS-CoV-2 variants of concern (VOC), B.1.1.7 (United Kingdom), B.1.351 (South Africa) and P.1 (Brazil), may reinforce this issue with the latter two being able to evade control by antibodies. We assessed humoral and T cell responses against SARS-CoV-2 WT and VOC and endemic human coronaviruses (hCoV) that were induced after single and double vaccination with BNT162b2. Despite readily detectable IgG against the receptor-binding domain (RBD) of the SARS-CoV-2 S protein at day 14 after a single vaccination, inhibition of SARS-CoV-2 S-driven host cell entry was weak and particularly low for the B.1.351 variant. Frequencies of SARS-CoV-2 specific T cells were low in many vaccinees after application of a single dose and influenced by immunity against endemic hCoV. The second vaccination significantly boosted T cell frequencies reactive for WT, B.1.1.7 and B.1.351 variants. These results call into question whether neutralizing antibodies significantly contribute to protection against COVID-19 upon single vaccination and suggest that cellular immunity is central for the early defenses against COVID-19.
RESUMO
BackgroundDuring the current pandemic, healthcare professionals (HCP) have been at the frontline of the crisis. Serological screening may help in identifying severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) prevalence. However, given the rapidly evolving situation in spring 2020, many questions regarding coronavirus disease 2019 (COVID-19) infection risk and utility of serological testing remained unanswered. To address these questions, we initiated the COVID-19 Contact (CoCo) study at Hannover Medical School, a large university hospital in Northern Germany and affiliated care providers. MethodsThe CoCo study is an ongoing, prospective, longitudinal, observational study in HCP and individuals with potential contact to SARS-CoV-2. It monitors anti-SARS-CoV-2 immunoglobulin serum levels and collects information on symptoms of respiratory infection, work and home environment, and self-perceived SARS-CoV-2 infection risk. Inclusion criteria are (1) working as HCP in clinical care at our university centre, affiliated hospitals or private practices, (2) written informed consent and (3) age >18 years. Exclusion criteria are (1) refusal to give informed consent and (2) contraindication to venepuncture. Study participants are asked to provide weekly to six-monthly samples (7.5 ml serum and 7.5 ml EDTA blood) and fill out a questionnaire. Since March 2020, around 1250 HCP have been included in the study. At each study visit, sera are screened for anti-SARS-CoV-2 spike protein 1 (S1) immunoglobulin G (IgG) by enzyme-linked immunosorbent assay (ELISA). Positive or borderline positive samples are re-assessed with an alternative serological test. Individual results for each study participant are made available online via a dedicated study website. This study also aims to compare different serological testing assays, as well as explore further humoral and cellular immune markers. Study protocols are continually adapted to the rapidly evolving situation of the current pandemic. DiscussionThis ongoing prospective study will aim to answer central questions on the prevalence and kinetics of anti-SARS-CoV-2-humoral immune responses and the validity of serological testing of HCP in a region with high healthcare standard and comparatively low COVID-19 prevalence. As such, our results are highly relevant to other regions and may support HCP around the world in managing this unprecedented situation. Trial registrationGerman Clinical Trial Registry, DRKS00021152. Registered 4th April 2020 -retrospectively registered, https://www.drks.de/drks_web/navigate.do?navigationId=trial.HTML&TRIAL_ID=DRKS00021152 Protocol summary O_TBL View this table: org.highwire.dtl.DTLVardef@1066beborg.highwire.dtl.DTLVardef@9734b4org.highwire.dtl.DTLVardef@1052a3dorg.highwire.dtl.DTLVardef@183b87org.highwire.dtl.DTLVardef@ec4318_HPS_FORMAT_FIGEXP M_TBL C_TBL
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BackgroundSerology testing is explored for epidemiological research and to inform individuals after suspected infection. During the COVID-19 pandemic, frontline healthcare professionals (HCP) may be at particular risk for infection. No longitudinal data on functional seroconversion in HCP in regions with low COVID-19 prevalence and low pre-test probability exist. MethodsIn a large German university hospital, we performed weekly questionnaire assessments and anti-SARS-CoV-2 IgG measurements with various commercial tests, a novel surrogate virus neutralization test, and a neutralization assay using live SARS-CoV-2. ResultsFrom baseline to week six, n=1,080 screening measurements for anti-SARS CoV-2 (S1) IgG from n=217 frontline HCP (65% female) were performed. Overall, 75.6% of HCP reported at least one symptom of respiratory infection. Self-perceived infection probability declined over time (from mean 20.1% at baseline to 12{middle dot}4 % in week six, p<0.001). In sera of convalescent PCR-confirmed COVID-19 patients, we measured high anti-SARS-CoV-2 IgG levels, obtained highly concordant results from ELISAs using e.g. the S1 spike protein domain and the nucleocapsid protein (NCP) as targets, and confirmed antiviral neutralization. However, in HCP the cumulative incidence for anti-SARS-CoV-2 (S1) IgG was 1.86% for positive and 0.93% for equivocal positive results over the six week study period. Except for one HCP, none of the eight initial positive results were confirmed by alternative serology tests or showed in vitro neutralization against live SARS CoV-2. The only true seroconversion occurred without symptoms and mounted strong functional humoral immunity. Thus, the confirmed cumulative incidence for neutralizing anti-SARS-CoV-2 IgG was 0.47%. ConclusionWhen assessing anti-SARS-CoV-2 immune status in individuals with low pre-test probability, we suggest confirming positive results from single measurements by alternative serology tests or functional assays. Our data highlight the need for a methodical serology screening approach in regions with low SARS-CoV-2 infection rates.
