Role of IgM Memory B Cells and Spleen Function in COVID-19.

IgM memory B cells, are a peculiar subset of memory B cells, which probably originates in the spleen and outside germinal centers and provide a rapid line of defence against mucosal infections. Their role in counteracting COVID-19 is still elusive but, recent evidence, mainly boosted by studies on spleen function/involvement in COVID-19, seems to support the notion that this subset of memory B cells could exert a protective role against this virus, along with other coronaviruses, particularly in the acute setting of the infection, as outlined by worst clinical outcomes observed in unvaccinated patients with impaired IgM B memory response and spleen function. Herein we critically summarise the current landscape of studies on IgM memory B cells, focusing on the clinical impact of their depletion, by comparing the COVID-19-related splenic dysfunction with other hypo- and asplenic conditions and by adding recent data on follow-up studies and postulate a mechanistic explanation for their reduced numbers. The early detection of an impaired IgM memory B cell response in patients with COVID-19 may contribute to their improved care through different strategies, such as through tailored vaccine strategies, prompt hospital admission and/or administration of anti-infective treatments, thus resulting in an better prognosis, although at present management algorithms are still unavailable. Moreover, further studies with longer follow-up are needed to assess the evolution of COVID-19-associated/exacerbated immune deficit.

Vaccination Status and Attitudes towards Vaccines in a Cohort of Patients with Celiac Disease.

(1) Background: The identification of vaccination status and attitudes towards vaccines among celiac disease (CD) patients is of great importance, but it has not yet been investigated. The aim of this study was to investigate coverage against vaccine-preventable diseases (VPDs), attitudes towards vaccinations, and its determinants among CD patients. (2) Methods: An anonymous web-based validated questionnaire was sent to a mailing list of CD adult patients. Patients were asked to self-report their previous vaccinations and attitudes towards vaccinations, which were defined as positive, negative, and partially positive/negative. The influencing factors towards vaccinations were investigated, and crude and adjusted odds ratios (AdjORs) with 95% confidence intervals (CIs) were calculated. (3) Results: The questionnaire was sent to 412 patients, with a response rate of 31.6% (130 patients, 105 women, median age 40 years, interquartile range 36-51). Patients self-reported vaccination against the following diseases: 73.8% tetanus, 42.3% flu, 20% measles, mumps and rubella, 19.2% meningitis, and 16.2% pneumococcus. Thirty-two people (24.6%) did not remember all of their previous vaccinations. In total, 104 (80%) respondents had a positive attitude towards vaccines, 25 (19.2%) a partially positive/negative one, and 1 a negative one. The determinants significantly influencing the positive attitude were being a graduate (AdjORs 7.49) and a belief in the possible return of VPDs with declining vaccination coverage rates (AdjORs 7.42), while the use of complementary and alternative medicines (AdjORs 0.11) and past negative experience (AdjORs 0.16) were associated with a negative attitude. (4) Conclusions: Despite four out of five CD patients showing a strong positive attitude towards vaccinations, one out of five had a partially negative one. Only a minority (16-20%) reported being vaccinated against some VPDs potentially harmful to their CD because of hyposplenism, such as meningitis and pneumococcus. The low vaccination rate against some VPDs, in spite of the 80% of CD patients stating a positive attitude towards vaccination, may be explained in part by patients' vaccine hesitancy and in part by a possible role of physicians in under-prescribing vaccinations to these patients. These results may be a starting point for developing specific vaccination campaigns to increase vaccination rates against VPDs in CD patients.