The COVID-19 pandemic represents a global health problem, which has been mitigated by the opportune introduction of vaccination programs. Although we already know the benefit that vaccines provide, these are not exempt from adverse events which can be mild to deadly, such as idiopathic inflammatory myopathies, in which a temporal association has not been defined. It is for this reason that we carried out a systematic review of all reported cases of vaccination against COVID-19 and myositis. To identify previously reported cases of idiopathic inflammatory myopathies associated with vaccination against SARS-CoV-2 we registered this protocol on the website of PROSPERO with identification number CRD42022355551. Of the 63 publications identified in MEDLINE and 117 in Scopus, 21 studies were included, reporting 31 cases of patients with vaccination-associated myositis. Most of these cases were women (61.3%); mean age was 52.3 years (range 19-76 years) and mean time of symptom onset post-vaccination was 6.8 days. More than half of the cases were associated with Comirnaty, 11 cases (35.5%) were classified as dermatomyositis, and 9 (29%) as amyopathic dermatomyositis. In 6 (19.3%) patients another probable trigger was identified. Case reports of inflammatory myopathies associated with vaccination have heterogeneous presentations without any specific characteristics: as a consequence, it is not possible to ensure a temporal association between vaccination and the development of inflammatory myopathies. Large epidemiological studies are required to determine the existence of a causal association.

COVID-19 affects the population unequally with a higher impact on aged and immunosuppressed people. Hence, we assessed the effect of SARS-CoV-2 vaccination in immune compromised patients (older adults and oncohematologic patients), compared with healthy counterparts. While the acquired humoral and cellular memory did not predict subsequent infection 18 months after full immunization, spectral and computational cytometry revealed several subsets within the CD8+ T-cells, B-cells, NK cells, monocytes and CD45RA+CCR7- Tγδ cells differentially expressed in further infected and non-infected individuals not just following immunization, but also prior to that. Of note up to 7 subsets were found within the CD45RA+CCR7- Tγδ population with some of them being expanded and other decreased in subsequently infected individuals. Moreover, some of these subsets also predicted COVID-induced hospitalization in oncohematologic patients. Therefore, we hereby have identified several cellular subsets that, even before vaccination, strongly related to COVID-19 vulnerability as opposed to the acquisition of cellular and/or humoral memory following vaccination with SARS-CoV-2 mRNA vaccines.