Vaccines are essential public health tools with a favorable safety profile and prophylactic effectiveness that have historically played significant roles in reducing infectious disease burden in populations, when the majority of individuals are vaccinated. The COVID-19 vaccines are expected to have similar positive impacts on health across the globe. While serious allergic reactions to vaccines are rare, their underlying mechanisms and implications for clinical management should be considered to provide individuals with the safest care possible. In this review, we provide an overview of different types of allergic adverse reactions that can potentially occur after vaccination and individual vaccine components capable of causing the allergic adverse reactions. We present the incidence of allergic adverse reactions during clinical studies and through post-authorization and post-marketing surveillance and provide plausible causes of these reactions based on potential allergenic components present in several common vaccines. Additionally, we review implications for individual diagnosis and management and vaccine manufacturing overall. Finally, we suggest areas for future research.

Background: Mutations in the filaggrin gene (FLG) affect epidermal barrier function and increase the risk of atopic dermatitis (AD). We hypothesized that FLG mutations affect immune cell composition in a general pediatric population. Therefore, we investigated if school-aged children with and without FLG mutations have differences in immune cell numbers. Methods: This study was embedded in a population-based prospective cohort study, the Generation R Study, and included 523 children of European genetic ancestry aged 10 years. The most common FLG mutations in the European population (R501X, S1085CfsX36, R2447X and S3247X) were genotyped. Additionally, 11-color flow cytometry was performed on peripheral blood samples to determine helper T (Th), regulatory T (Treg) and CD27+ and CD27- memory B cells. Sensitivity analysis was performed in 102 AD cases, assessed by parental questionnaires. Results: FLG mutations were observed in 8.4% of the total population and in 15.7% of the AD cases. Children with any FLG mutation had higher Th22 cell numbers compared to FLG wild-type children. Children with and without FLG mutations had no difference in Th1, Th2, Th17, Treg or memory B cell numbers. Furthermore, in children with AD, FLG mutation carriership was not associated with differences in T- and B-cells or their subsets. Conclusions: School-aged children with FLG mutations have higher Th22 cell, which might suggest an immunological defense mechanism to an altered skin barrier function. No associations between Th or Treg cells and FLG mutations suggests that FLG mutations do not otherwise affect immune composition in a general pediatric population.

Background: Diagnostic tests for allergy rely on detecting allergen-specific IgE. Component-resolved diagnostics incorporate multiple defined allergen components to improve the quality of diagnosis and patient care. Objective: To develop a new approach for determining sensitization to specific allergen components that utilizes fluorescent protein tetramers for direct staining of IgE on blood basophils by flow cytometry. Methods: Recombinant forms of Lol_p_1 and Lol_p_5 proteins from ryegrass pollen (RGP) and Api_m_1 from honeybee venom (BV) were produced, biotinylated and tetramerized with streptavidin-fluorophore conjugates. Blood samples from 50 RGP-allergic, 41 BV-allergic and 26 controls were incubated with fluorescent protein tetramers for flow cytometric evaluation of basophil allergen binding and activation. Results: Allergen tetramers bound to and activated basophils from relevant allergic patients but not controls. Direct fluorescence staining of Api_m_1 and Lol_p_1 tetramers had greater positive predictive values than basophil activation for BV and RGP allergy, respectively, as defined with receiver operator characteristics (ROC) curves. Staining intensities of allergen tetramers correlated with allergen-specific IgE levels in serum. Inclusion of multiple allergens coupled with distinct fluorochromes in a single tube assay enabled rapid detection of sensitization to both Lol_p_1 and Lol_p_5 in RGP-allergic patients and discriminated between controls, BV-allergic and RGP-allergic patients. Conclusion: Our novel flow cytometric assay, termed CytoBas, enables rapid and reliable detection of clinically relevant allergic sensitization. The intensity of fluorescent allergen tetramer staining of basophils has a high positive predictive value for disease and the assay can be multiplexed for a component-resolved and differential diagnostic test for allergy.

In December 2019, China reported the first cases of the coronavirus disease 2019 (COVID-19). This disease, caused by the severe acute respiratory syndrome-related coronavirus 2 (SARS-CoV-2), has developed into a pandemic. To date it has resulted in ~5.6 million confirmed cases and caused 353,334 related deaths worldwide. Unequivocally, the COVID-19 pandemic is the gravest health and socio-economic crisis of our time. In this context, numerous questions have emerged in demand of basic scientific information and evidence-based medical advice on SARS-CoV-2 and COVID-19. Although the majority of the patients show a very mild, self-limiting viral respiratory disease, many clinical manifestations in severe patients are unique to COVID-19, such as severe lymphopenia and eosinopenia, extensive pneumonia, a “cytokine storm” leading to acute respiratory distress syndrome, endothelitis, thrombo-embolic complications and multiorgan failure. The epidemiologic features of COVID-19 are distinctive and have changed throughout the pandemic. Vaccine and drug development studies and clinical trials are rapidly growing at an unprecedented speed. However, basic and clinical research on COVID-19-related topics should be based on more coordinated high-quality studies. This paper answers pressing questions, formulated by young clinicians and scientists, on SARS-CoV-2, COVID-19 and allergy, focusing on the following topics: virology, immunology, diagnosis, management of patients with allergic disease and asthma, treatment, clinical trials, drug discovery, vaccine development and epidemiology. Over 140 questions were answered by experts in the field providing a comprehensive and practical overview of COVID-19 and allergic disease.