New-onset Adult-onset Still's disease-like syndrome after ChAdOx1 nCoV-19 vaccination-a case series with review of literature.

We report a series of 3 Adult-onset Still's disease (AOSD)-like presentations in previously healthy females following vaccination with the ChAdOx1 nCoV-19 vaccine, and also compare them with similar cases reported in literature through a PubMed database search. Our first patient had a high spiking bi-quotidian type of fever with myalgia, sore throat, and arthritis with onset 10-day post-vaccination, with laboratory features of hyper inflammation responding to only naproxen. She was off treatment after 2 months. The second patient, with onset 3-week post-vaccination, had a more severe illness, requiring high dose immunosuppression. In our third case, the onset of illness was slightly delayed i.e., 3-month post-vaccination, but she had the most severe disease with macrophage activation syndrome at presentation requiring immunosuppression and biologicals. The underlying mechanism may be linked to the activation of Toll-like receptors (TLR)-TLR-7 and TLR-9-leading to a robust immune response. These 3 cases highlight the immunogenicity of COVID-19 vaccines, with the possibility of occurrence of new-onset systemic hyper-inflammation illness which can happen a few days following the vaccination, sometimes even delayed to months, and can range in severity from mild to even life-threatening. More cases need to be studied to understand the profile and prognosis of these syndromes in the long run.