Although the World Health Organisation has declared the end of the pandemic phase of COVID-19, the situation remains challenging especially for immunocompromised people due to continuous mutations of SARS-CoV-2 that perpetuate the spread of this very contagious virus.1 A major advance in protection from COVID-19 has been the development of effective, constantly updated vaccines which are highly recommended for patients with autoimmune disorders such as immunobullous diseases.2 However, there is a paucity of data on the effect of immunosuppressive drugs on immunological responses to COVID-19 vaccines in this particular patient population. Therefore, similarly to what was previously described in patients with rheumatic diseases,3 we assessed the serological response to COVID-19 vaccination in patients with autoimmune blistering dermatoses. Data were prospectively collected from COVID-19-vaccinated pemphigus and pemphigoid patients who were treated with different immunomodulatory medications including rituximab and recruited in our dermatology department from May 2021 to October 2023. They were serologically screened for antibodies against SARS-CoV-2 using a commercial quantitative anti-SARS-CoV-2 spike protein antibody immunoassay (Roche). In rituximab-treated patients, the time between the most recent administration of the drug and the vaccine was recorded. The primary outcome was the presence of serological responsiveness to COVID-19 vaccination. A total of 25 patients with bullous pemphigoid (n = 10), pemphigus vulgaris (n = 11), and pemphigus foliaceus (n = 4) were included in this study. All subjects were fully vaccinated against COVID-19 (i.e., at least two doses of the Pfizer-BioNTech/Moderna vaccine or one dose of the Johnson & Johnson vaccine) at the time of the immunoassay. 19 patients (76%) were treated with more than one immunomodulatory medication during the assessment (Table 1). Using an antibody threshold level for the applied SARS-CoV-2 immunoassay that was proposed to confer protection in immunocompromised patients,4 we found that 17 of the 25 patients (68%) had a strong (i.e., protective) serological response to vaccination against COVID-19, while the remaining 8 patients (32%) had a negative/weak response to the vaccine. We observed a strong trend towards a higher serological response in association with the number of vaccines (p = 0.052). Although there was generally no significant relationship between the various immunomodulatory therapies and an impaired serological response to SARS-CoV-2 vaccination, among rituximab recipients, we noticed a significant difference in the length of the rituximab-vaccine time interval between those with a strong serological response compared with those with a negative/weak response (Table 1) (Figure 1). Besides the potential risk of a more severe COVID-19 course during B-cell-depleting therapy in patients with immunobullous diseases,5 a major concern is the risk of decreased immunogenicity of vaccination, as already described in other types of autoimmune diseases.3 In our study, a longer time span between the most recent rituximab exposure and last vaccine application was associated with a greater likelihood of a protective serological vaccine response, which may especially apply to patients who received vaccine booster doses. Similar results were obtained in patients with rheumatic diseases on anti-CD20 therapy and correlated with B-cell reconstitution, which usually occurs about 6–12 months post rituximab treatment.3 These data support our previously published and internationally well accepted recommendation to lengthen the time between the last rituximab treatment and the administration of the COVID-19 vaccines in patients with immunobullous diseases.2, 6 Nevertheless, it needs to be noted that, despite the rituximab-induced compromised humoral vaccine antibody response, SARS-CoV-2 vaccine-elicited specific T-cell-mediated responses may be preserved and confer partial protection from COVID-19 during B-cell-depleted states as recently shown in pemphigus vulgaris patients.7 Further studies with larger cohorts are needed to determine the responses to SARS-CoV-2 vaccines and optimisation of vaccination responsiveness in patients with autoimmune bullous diseases. M. Kasperkiewicz (conception/design of the work), B. Levian and D.T. Woodley (data collection), B. Levian and S. Tukaj (data analysis and interpretation), M. Kasperkiewicz (drafting the article), B. Levian, S. Tukaj, and D.T. Woodley (critical revision of the article); all authors discussed the results and contributed to the final manuscript. We thank Claire Stevens (University of Southern California) for her support with the data analysis. The authors declare no conflicts of interest. All patients in this manuscript have given written informed consent for participation in the study and the use of their deidentified, anonymized, aggregated data and their case details for publication; this study was approved by the institutional review board of the University of Southern California.