Patient inclusion criteria:  Diagnosis AD in early phase according to the IWG-2 criteria. Mini-Mental State Examination (MMSE) Score ≥20.  In-vivo evidence of Alzheimer´s pathology (one of the following):  Decreased Aβ42 together with increased t-tau or p-tau in CSF. Increased tracer retention on amyloid PET. Availability of a next of kin who knows the patient well and is willing to accompany the subject to all trial visits and give information about the patients functional level. Signed informed consent. The patient is judged fitted for the study and capable to cooperate in treatment and follow-up. Ability to communicate in Norwegian or another Scandinavian language.  Patient exclusion criteria:  Pregnancy or unwilling to use adequate birth control for the duration of and 6 months beyond study participation. Defined according to Clinical Trial Facilitation Group document "Recommendations related to contraception and pregnancy testing in clinical trials". Positive for Hepatitis B, Hepatitis C or HIV at screening. Not qualified to give consent at inclusion. Any other condition judged to interfere with the safety of the patient or the intent and conduct of the study.  Related to medical history:  Stroke Anaphylaxis Prior adverse reaction to any human blood product Any history of a blood coagulation disorder or hypercoagulability Congestive heart failure, defined as any previous heart failure hospitalization, or current symptomatic heart failure in New York heart Association class ≥II with reduced, mid-range or preserved ejection fraction. Coagulation defect or hypercoagulopathy Uncontrolled hypertension Renal failure Prior intolerance to intravenous fluids Recent history of uncontrolled atrial fibrillation Bone marrow transplant IgA deficiency Severe protein S deficiency Thrombocytopenia (platelets < 40 x 10 to the power of 9/L) Contraindication for Octaplasma  Related to medications or other treatments:  Any concurrent use of anticoagulant therapy, clopidogrel or acetylsalicylic acid/Dipyridamol in combination. Initiation or change in the dosage of a acetylcholine esterase inhibitor (AChEI) or memantine during the trial (week 0-52). Participants will be urged to start on AChEI when diagnosis is communicated, and must be on a stable dose for at least one month prior to screening. Concurrent participation in another treatment trial for AD. If there was prior participation, the last dose of the investigational agent must have been given at least 6 months prior to screening, except if the patient received placebo medication. Treatment with any human blood product, including intravenous immunoglobulin, during the 6 months prior to screening or during the trial. Concurrent daily treatment with benzodiazepines, typical or atypical antipsychotics, long-acting opioids, or other medications that is judged to interfere with cognition. Intermittent treatment with short-acting benzodiazepines or atypical antipsychotics may be permitted, provided that no dose is administered within 72 hours prior to cognitive assessment.  Related to magnetic resonance imaging:  Claustrophobia Any metallic surgical implant, like a pacemaker or clip that is incompatible with MRI.  Certain metallic implants like joint replacements may be permitted, provided that specific manufacturer specifications are available, and that the device is known to be safe for 7T MRI. In case a patient is not eligible for the 7T scanner, the 3T scanner will be used.