sElective Serotonin reuPtake inhibitoRs In posT-covid After COVID-19

Inclusion Criteria: * Adults aged 18 to 70 years * Severely fatigued (CIS fatigue score ≥ 35) at screening * Fatigue started/increased significantly after Covid-19 (self-declared) * Fatigue symptoms must be present for at least 3 months following the acute infection. * Self-reported confirmation of having a SARS-CoV-2 infection by: Positive SARS-CoV-2 nucleic acid amplification test (NAAT), such as PCR; Positive SARS-CoV-2 rapid diagnostic test, including home-administered tests; COVID-19 diagnosis by a medical specialist (GP or in-hospital), based on the above or other clinical test or assessments. The above information will not be verified in medical records. * Command of Dutch or English language to complete questionnaires * Able to participate in video calling. * Willing and able to provide informed consent * Allowing the trial team to exchange medical information that is relevant for the participants' safety and trial assessments with their GP and pharmacy. Exclusion Criteria: * Use of medication with interaction with fluvoxamine that cannot be discontinued * Hospitalized in the acute phase of Covid-19 * Psychiatric/somatic disorders that could explain the severity of fatigue * Neurodegenerative disorders (i.e. M Parkinson, Multiple sclerosis, M Alzheimer) * Suicidality (current or recent) (according to WHO suicide screener) * Starting or started with other medication intended to reduce post-covid symptoms during the last 2 months * Pregnancy (a positive urine or serum pregnancy test) or unwilling to use standard contraception * Brugada- or Long QT interval syndrome * epilepsy, porphyria, history of severe liver impairment * known allergies to fluvoxamine or placebo/excipients * known current alcohol or drug use problems. * Bleeding disorders and past medical history of bleeding gastric or duodenal ulcers or other significant bleeding disorders * claustrophobia (optional MRI substudy) * having metal implants (optional MRI substudy) * inability to lay still for 45 minutes (optional MRI substudy) * Neurotrauma/ large stroke or brain abnormalities interfering with image analyses (optional MRI substudy) * Inability to come to the Amsterdam UMC (optional MRI substudy).