Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS): This condition is characterized by a severe skin reaction, often with mucosal involvement, and can affect multiple organs, leading to failure. The patient's history of receiving multiple vaccines followed by a severe reaction, elevated WBCs, and the presence of papules all over the body supports this diagnosis. The timeline and the multiorgan involvement also align with DRESS syndrome.

Stevens-Johnson Syndrome (SJS) / Toxic Epidermal Necrolysis (TEN): These are severe skin and mucous membrane disorders usually caused by an adverse reaction to medications or infections. The patient's severe skin reaction, mucosal lesions, and multiorgan failure could suggest SJS/TEN, although the absence of widespread skin necrosis might lean more towards SJS.
Serum Sickness-like Reaction (SSLR): This condition can occur after vaccination and is characterized by symptoms such as rash, arthralgias, and sometimes renal involvement. The patient's symptoms of severe leg pain, foot swelling, and papules could be consistent with SSLR, although the severity of multiorgan failure might be less typical.
Vasculitis: Conditions like Henoch-Schönlein purpura or other forms of vasculitis could explain the skin lesions, multiorgan involvement, and the severe reaction post-vaccination. However, the specific pattern of organ involvement and the presence of papules all over the body might not fully align with typical vasculitis presentations.

Septic Shock: Although the patient has negative bacterial cultures, septic shock from a non-bacterial source (e.g., viral or fungal) or a false-negative culture due to prior antibiotic use could explain the multiorgan failure. It's crucial to continue investigating for any infectious cause.
Autoimmune Hemolytic Anemia (AIHA) or other Hematologic Emergencies: These conditions could lead to multiorgan failure and have cutaneous manifestations. The elevated WBCs and the context of the reaction could potentially mask an underlying hematologic issue.

Kawasaki Disease: Although typically seen in younger children, Kawasaki disease can occur in adults and is characterized by fever, rash, mucous membrane changes, and potential for multiorgan involvement, including cardiac issues.
Erythema Multiforme: This is an immune-mediated disorder that can be triggered by infections or medications, characterized by target lesions on the skin. While it can involve mucous membranes and have systemic symptoms, multiorgan failure is less common.
Acute Intermittent Porphyria: This rare genetic disorder can cause severe abdominal pain, neurological symptoms, and sometimes skin lesions, but it's less likely given the context of vaccination and the specific pattern of symptoms described.