The Effect of Probiotic Supplementation on SARS-CoV-2 Antibody Response After COVID-19

Inclusion Criteria: 1. Signed informed consent 2. Age between 18-60 Exclusion Criteria: 1. Previous diagnosis of COVID-19 (by positive PCR) or previous confirmation of seropositivity to SARS-CoV-2 2. Body Mass Index over 35 or under 16 3. Current diagnosis of cancer or ongoing cancer treatment in the last 12 months 4. Diabetes mellitus 5. Cardiovascular disorder in need of pharmaceutical treatment 6. Chronic kidney disease 7. Chronic lung disease with decreased lung capacity 8. Chronic liver disease with liver cirrhosis 9. Current diagnosis of dementia, severe depression, major psychiatric disorder, or other incapacity for adequate cooperation 10. Chronic neurological/neurodegenerative disease (e.g. Parkinson's disease) 11. Decreased function of the adrenal cortex (e.g. Addison's disease) 12. Autoimmune disease (e.g. rheumatoid arthritis) 13. Chronic pain syndromes (e.g. fibromyalgia) 14. Pregnancy or breast-feeding 15. Immunodeficiency due to disease or ongoing medical treatment 16. Regular intake of anti-inflammatory and/or other immunosuppressive medication within the last 3 months 17. Use of anti-depressants within the last 3 months 18. Antimicrobial treatment within the last 12 weeks before baseline sampling 19. Regular intake of probiotics, as well as nutritional supplements or herb products that might affect intestinal function within the last 4 weeks if the investigator considers that those could affect study outcome 20. Inability to maintain current diet and lifestyle during the study period 21. Alcohol or drug abuse 22. Any clinically significant present or past disease/condition which the investigator considers to possibly interfere with the study outcome or increase the risk for severe form of COVID-19