Could a fiber supplement boost your vaccine?

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria: 1. Body Mass Index (BMI) 18.5 - 30.9 kg/m2 2. inadequate total dietary fiber intake defined as: * Females 18 - 30 years old, less than 28 g/day * Females 31 - 50 years old, less than 25 g/day * Females 51+ year old, less than 22 g/day * Males 18 - 30 years old, less than 34 g/day * Males 31 - 50 years old, less than 31 g/day * Males 51+ years old, less than 28 g/day Exclusion Criteria: 1. blood pressure greater than or equal to 140/90 mmHg 2. has HIV/AIDS or another disease that affects the immune system 3. has any kind of cancer 4. inability to lift 30 pounds with assistance (for transporting refrigerated stool containers) 5. decline to take an HIV blood test 6. pregnant or lactating women 7. refusal to take a pregnancy test 8. female subjects: refusal to use a method of birth control 1 week prior to the administration of the vaccine, 1 week during the vaccine, and 1 week after the vaccine 9. allergy to vaccine components, i.e. thimerosal and enteric-coated capsules 10. allergy to oral typhoid vaccine 11. use of anti-inflammatory medications, i.e. nonsteroidal anti-inflammatory drugs (NSAID), aspirin, 3 or more times per month 12. use of sulfonamides or antibiotics 3 months prior to the receipt of Ty21a vaccine. 13. use of anti-hypertensive drugs, i.e. beta blockers, diuretics, calcium channel blockers 14. use of anti-malaria drugs, i.e. mefloquine, chloroquine, and proguanil 15. use of drugs that affects the immune system, i.e. immunosuppressants, immune-modifying drugs, corticosteroids, i.e. cortisone, prednisone, methylprednisolone, for 2 weeks or longer 16. use of biologics, i.e. Lantus, Remicade, Rituxan, Humira, Herceptin, Avastin, Lucentis, Enbrel for 2 weeks or longer 17. undergoing cancer treatment with radiation or drugs 18. greater than 10 years residence in a typhoid-endemic area 19. receipt of typhoid vaccine in the last 5 years 20. receipt of any vaccine two weeks prior to receipt of Ty21a vaccine 21. individuals at increased risk of developing complications from a live, bacterial vaccine 22. history of typhoid fever 23. history of primary immune deficiency or autoimmune disease 24. history of acute or chronic gastrointestinal (GI) disorder, i.e. Crohn's disease, irritable bowel syndrome, gastric ulcer 25. diarrheal illness (defined as passing 3 or more abnormally loose or watery stool in a 24 hour period) or persistent vomiting 2 weeks prior to the study 26. history of chronic illnesses, i.e. diabetes, cardiovascular disease, cancer, gastrointestinal malabsorption or inflammatory diseases, kidney disease, autoimmune disorders, HIV, liver disease, including hepatitis B and C 27. asthma if taking medication on a daily basis 28. recent surgery (within 3 months) 29. history of GI surgery 30. recent hospitalization (within 3 months) 31. fever (within 2 weeks) 32. unwillingness to discontinue probiotic, prebiotic, or other supplements (except Recommended Dietary Allowance-level vitamin and mineral supplements), fiber supplements, or food and beverage products containing inulin, chicory root fiber, or maltodextrin during the study 33. not having at least one arm vein suitable for blood drawing 34. unwilling or uncomfortable with blood draws and stool collections 35. regular blood or blood product donation and refusal to suspend donation 36. current participation in another research study 37. unable to fast for 12-16 hours 38. have fewer than 3 bowel movements per week 39. consuming one or more servings of added-inulin foods per day over the past month