Primary ChAdOx1 vaccination does not reactivate pre-existing, cross-reactive immunity.

Currently available COVID-19 vaccines include inactivated virus, live attenuated virus, mRNA-based, viral vectored and adjuvanted protein-subunit-based vaccines. All of them contain the spike glycoprotein as the main immunogen and result in reduced disease severity upon SARS-CoV-2 infection. While we and others have shown that mRNA-based vaccination reactivates pre-existing, cross-reactive immunity, the effect of vector vaccines in this regard is unknown. Here, we studied cellular and humoral responses in heterologous adenovirus-vector-based ChAdOx1 nCOV-19 (AZ; Vaxzeria, AstraZeneca) and mRNA-based BNT162b2 (BNT; Comirnaty, BioNTech/Pfizer) vaccination and compared it to a homologous BNT vaccination regimen. AZ primary vaccination did not lead to measurable reactivation of cross-reactive cellular and humoral immunity compared to BNT primary vaccination. Moreover, humoral immunity induced by primary vaccination with AZ displayed differences in linear spike peptide epitope coverage and a lack of anti-S2 IgG antibodies. Contrary to primary AZ vaccination, secondary vaccination with BNT reactivated pre-existing, cross-reactive immunity, comparable to homologous primary and secondary mRNA vaccination. While induced anti-S1 IgG antibody titers were higher after heterologous vaccination, induced CD4+ T cell responses were highest in homologous vaccinated. However, the overall TCR repertoire breadth was comparable between heterologous AZ-BNT-vaccinated and homologous BNT-BNT-vaccinated individuals, matching TCR repertoire breadths after SARS-CoV-2 infection, too. The reasons why AZ and BNT primary vaccination elicits different immune response patterns to essentially the same antigen, and the associated benefits and risks, need further investigation to inform vaccine and vaccination schedule development.

SARS-CoV-2 mRNA vaccinations fail to elicit humoral and cellular immune responses in patients with multiple sclerosis receiving fingolimod.

BACKGROUND: SARS-CoV-2 mRNA vaccination of healthy individuals is highly immunogenic and protective against severe COVID-19. However, there are limited data on how disease-modifying therapies (DMTs) alter SARS-CoV-2 mRNA vaccine immunogenicity in patients with autoimmune diseases. METHODS: As part of a prospective cohort study, we investigated the induction, stability and boosting of vaccine-specific antibodies, B cells and T cells in patients with multiple sclerosis (MS) on different DMTs after homologous primary, secondary and booster SARS-CoV-2 mRNA vaccinations. Of 126 patients with MS analysed, 105 received either anti-CD20-based B cell depletion (aCD20-BCD), fingolimod, interferon-ß, dimethyl fumarate, glatiramer acetate, teriflunomide or natalizumab, and 21 were untreated MS patients for comparison. RESULTS: In contrast to all other MS patients, and even after booster, most aCD20-BCD- and fingolimod-treated patients showed no to markedly reduced anti-S1 IgG, serum neutralising activity and a lack of receptor binding domain-specific and S2-specific B cells. Patients receiving fingolimod additionally lacked spike-reactive CD4+ T cell responses. The duration of fingolimod treatment, rather than peripheral blood B and T cell counts prior to vaccination, determined whether a humoral immune response was elicited. CONCLUSIONS: The lack of immunogenicity under long-term fingolimod treatment demonstrates that functional immune responses require not only immune cells themselves, but also access of these cells to the site of inoculation and their unimpeded movement. The absence of humoral and T cell responses suggests that fingolimod-treated patients with MS are at risk for severe SARS-CoV-2 infections despite booster vaccinations, which is highly relevant for clinical decision-making and adapted protective measures, particularly considering additional recently approved sphingosine-1-phosphate receptor antagonists for MS treatment.

Cutting Edge: Serum but Not Mucosal Antibody Responses Are Associated with Pre-Existing SARS-CoV-2 Spike Cross-Reactive CD4+ T Cells following BNT162b2 Vaccination in the Elderly.

Advanced age is a main risk factor for severe COVID-19. However, low vaccination efficacy and accelerated waning immunity have been reported in this age group. To elucidate age-related differences in immunogenicity, we analyzed human cellular, serological, and salivary SARS-CoV-2 spike glycoprotein-specific immune responses to the BNT162b2 COVID-19 vaccine in old (69-92 y) and middle-aged (24-57 y) vaccinees compared with natural infection (COVID-19 convalescents, 21-55 y of age). Serological humoral responses to vaccination excee-ded those of convalescents, but salivary anti-spike subunit 1 (S1) IgA and neutralizing capacity were less durable in vaccinees. In old vaccinees, we observed that pre-existing spike-specific CD4+ T cells are associated with efficient induction of anti-S1 IgG and neutralizing capacity in serum but not saliva. Our results suggest pre-existing SARS-CoV-2 cross-reactive CD4+ T cells as a predictor of an efficient COVID-19 vaccine-induced humoral immune response in old individuals.

Cross-reactive CD4+ T cells enhance SARS-CoV-2 immune responses upon infection and vaccination.

The functional relevance of preexisting cross-immunity to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a subject of intense debate. Here, we show that human endemic coronavirus (HCoV)­reactive and SARS-CoV-2­cross-reactive CD4+ T cells are ubiquitous but decrease with age. We identified a universal immunodominant coronavirus-specific spike peptide (S816-830) and demonstrate that preexisting spike- and S816-830­reactive T cells were recruited into immune responses to SARS-CoV-2 infection and their frequency correlated with anti­SARS-CoV-2-S1-IgG antibodies. Spike­cross-reactive T cells were also activated after primary BNT162b2 COVID-19 messenger RNA vaccination and displayed kinetics similar to those of secondary immune responses. Our results highlight the functional contribution of preexisting spike­cross-reactive T cells in SARS-CoV-2 infection and vaccination. Cross-reactive immunity may account for the unexpectedly rapid induction of immunity after primary SARS-CoV-2 immunization and the high rate of asymptomatic or mild COVID-19 disease courses.

COVID-19: Effect-modelling of vaccination in Germany with regard to the mutant strain B.1.1.7 and occupancy of ICU facilities.

BACKGROUND: The characteristics of the COVID-19 pandemic in Europe have changed since the initial outbreak in 2019 due to the emergence of more contagious mutant strains, notably the B.1.1.7 variant. This has resulted in the rapid implementation of vaccination programs in an effort to control the spread of the disease. AIMS: To model the effect of vaccination on the course of the pandemic in Germany taking into account observational data and the appearance of viral mutant B.1.1.7. MATERIALS AND METHODS: An effect model based on the Batman-SIZ algorithm was developed, taking into account both the parent and the B.1.1.7 mutant strains of the SARS-CoV-2 coronavirus and using input parameters obtained from observational data for January - March 2021. RESULTS: Effect-modelling using 3 different vaccination scenarios with different rates of vaccination involving 67 million persons (priority groups 1 - 5) and completed within 134 days compared to 318 days beginning February 24, 2021, showed a reduction in the number of infected persons from ca. 12.5 million to ca. 4.5 million with quantitively similar benefits regarding the occupancy and a critical burden on ICU facilities. CONCLUSION: The effect of vaccination in reducing the daily number of new infections, the total number of infections and the occupancy of intensive-care facilities in hospitals is proportional to the speed with which the target population are vaccinated.

Prevalence of SARS-COV-2 positivity in 516 German intensive care and emergency physicians studied by seroprevalence of antibodies National Covid Survey Germany (NAT-COV-SURV).

Healthcare personnel are at risk to aquire the corona virus disease 2019 (COVID-19) caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). We evaluated the prevalence of SARS-CoV-2 antibodies and positive nasopharyngeal reverse transcriptase polymerase-chain reaction (RT-PCR) tests in German intensive care and emergency physicians. Physicians attending intensive care and emergency medicine training courses between June 16th and July 2nd 2020 answered a questionnaire and were screened for SARS-CoV-2 antibodies via automated electrochemiluminiscence immunoassay. We recruited 516 physicans from all parts of Germany, 445/516 (86%) worked in high risk areas, and 379/516 (73%) had treated patients with COVID-19. The overall positive rate was 18/516 (3.5%), 16/18 (89%) had antibodies against SARS-COV-2, another 2 reported previous positive RT-PCR results although antibody testing was negative. Of those positive, 7/18 (39%) were unaware of their infection. A stay abroad was stated by 173/498 (35%), mostly in Europe. 87/516 (17%) reported a febrile respiratory infection after January 1st 2020 which was related to SARS-CoV-2 in 4/87 (4.6%). Contact to COVID-19 positive relatives at home was stated by 22/502 (4.4%). This was the only significant risk factor for Covid-19 infection (Fisher´s exact test, p = 0.0005). N95 masks and eye protection devices were available for 87% and 73%, respectively. A total of 254/502 (51%) had been vaccinated against seasonal influenza. The overall SARS-CoV-2 infection rate of german physicians from intensive care and emergency medicine was low compared to reports from other countries and settings. This finding may be explained by the fact that the German health care system was not overwhelmed by the first wave of the SARS-CoV-2 pandemic.

COVID-19: Predictions for SARS-CoV-2 vaccination on the course of the pandemic and critical occupancy of intensive-care facilities in Germany.

AIMS OF THE STUDY: To obtain predictions using the Modified Bateman SIZ Model for the effects of vaccination on the course of the COVID-19 pandemic in Germany. MATERIALS AND METHODS: Start parameters for the model were obtained from observational data after data-smoothing to reduce between-day variation. Three scenarios, 1) no vaccination, 2) vaccination of 60% of the population over 12 months, 3) vaccination of 60% of the population over 7 months were examined. The effects of changes in tα (doubling-time for the spread of infection, known to be slower in the summer months) and tß (half-life of recovery from infection) on the daily number of infectious persons, the cumulative number of infected persons, and the duration of critical occupancy of intensive-care units were also determined. RESULTS: Vaccination produced a marked and rapid reduction in the number of infectious persons (up to -60%) and the total number of infected persons (up to -70%). A 7-month vaccination strategy was significantly more effective than a 12-month strategy. The summer effect came too late to have an additional effect on the spread of infection. Vaccination was predicted to reduce the duration of critical occupancy of intensive-care facilities by ~ 70%. DISCUSSION: The predictions are based on the assumptions that lockdown conditions are maintained and vaccine availability is not limiting. CONCLUSION: Predictions made using the model show that vaccination with a SARS-CoV-2 vaccine can markedly reduce the spread of the COVID-19 disease and the period of critical occupancy of intensive-care facilities in Germany.

Predictions for the COVID-19 pandemic in Germany using the modified Bateman SIZ model.

AIMS OF THE STUDY: To obtain predictions for the course of the COVID-19 pandemic in Germany using the modified Bateman SIZ model and input variables based on the status quo in July 2020. To predict the effect of a change in tα on the course of the pandemic. To evaluate the robustness and sensitivity of the model in response to a change in the input parameters. MATERIALS AND METHODS: Start parameters for the modified Bateman SIZ model were obtained from observational data published by the Robert-Koch-Institute in Berlin for the period June 1 to July 13, 2020. The robustness and sensitivity of the model were determined by changing the input parameter for the doubling-time (tα) by ± 5% and ± 10%. RESULTS: The predictions show that small changes, ± 5%, in the doubling-time, tα for the rate of increase in the number of new infections, can have a major effect, both positive and negative, on the course of the pandemic. The model predicted that the number of persons infected with the virus would reach 1 million within 8 years. A 5% longer tα would reduce the number of infected persons by ~ 75%. In contrast, a 5% shorter doubling-time would increase the number of infections over 8 years to ~ 9 million when the number of infectious persons would exceed 100,000 at the end of 2022. The pandemic is predicted to have disappeared by the end of 2024. DISCUSSION: Predictions for the course of the COVID-19 pandemic in Germany based on the status quo up to July 13, 2020 have been obtained using the modified Bateman SIZ model. There are several important assumptions necessary to apply the model and thus the results must be interpreted with caution. The model, previously used to predict the course of the COVID-19 pandemic in the city of Heidelberg (pop. 166,000) gives comparable predictive data for the whole of Germany (pop. 83 million) and thus appears to be both sensitive and robust. CONCLUSION: Since a shorter doubling-time for the number of infectious persons by only 5% would result in a major clinical emergency, interventional measures such as vaccination are urgently needed. Taking into consideration that a SARS-CoV-2 vaccine is not yet available and the efficacy of the Corona-Warn-App has yet to be shown, a relaxation in the lockdown conditions in Germany in 2020 appears premature.

SARS-CoV-2-reactive T cells in healthy donors and patients with COVID-19.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused the rapidly unfolding coronavirus disease 2019 (COVID-19) pandemic1,2. Clinical manifestations of COVID-19 vary, ranging from asymptomatic infection to respiratory failure. The mechanisms that determine such variable outcomes remain unresolved. Here we investigated CD4+ T cells that are reactive against the spike glycoprotein of SARS-CoV-2 in the peripheral blood of patients with COVID-19 and SARS-CoV-2-unexposed healthy donors. We detected spike-reactive CD4+ T cells not only in 83% of patients with COVID-19 but also in 35% of healthy donors. Spike-reactive CD4+ T cells in healthy donors were primarily active against C-terminal epitopes in the spike protein, which show a higher homology to spike glycoproteins of human endemic coronaviruses, compared with N-terminal epitopes. Spike-protein-reactive T cell lines generated from SARS-CoV-2-naive healthy donors responded similarly to the C-terminal region of the spike proteins of the human endemic coronaviruses 229E and OC43, as well as that of SARS-CoV-2. This results indicate that spike-protein cross-reactive T cells are present, which were probably generated during previous encounters with endemic coronaviruses. The effect of pre-existing SARS-CoV-2 cross-reactive T cells on clinical outcomes remains to be determined in larger cohorts. However, the presence of spike-protein cross-reactive T cells in a considerable fraction of the general population may affect the dynamics of the current pandemic, and has important implications for the design and analysis of upcoming trials investigating COVID-19 vaccines.