This project aims to test the hypothesis that oral consumption of a specific strain of the probiotic bacterium Lactobacillus fermentum (trademarked PCC®) is able to significantly enhance the immune response to a vaccine for influenza.

Inclusion Criteria:

• Persons must be adult men and women aged 18-49 years (have not reached 50th birthday).
• Persons must be able and willing to provide informed consent.
• Persons must be willing to receive the influenza vaccine (Fluvax®) given as an intramuscular injection.
• Persons must be willing to consume one gelatin capsule per day containing either probiotic bacteria or placebo (inactive substance) for the duration (42 days) of the study.
• Persons must be willing to provide blood specimens, each of 10 ml, collected by venepuncture.
• Persons must be willing to notify study personnel of a range of health effects by questionnaire.

Exclusion Criteria:

• Any health condition for which the influenza vaccine is not recommended including: chronic diseases of the pulmonary or cardiovascular systems (including asthma); chronic metabolic diseases (including diabetes); renal dysfunction; hemoglobinopathies; immune deficiency diseases (including HIV infection) or on-going immunosuppressive therapy.
• Currently pregnant; nursing mothers; or planning a pregnancy within one month of vaccination.
• Allergy to latex, egg, or egg protein, or the antibiotics neomycin or polymyxin.
• A prior serious reaction to a vaccine, or have had Guillain-Barre syndrome.
• Received an influenza vaccine in the past.
• Received any other vaccine within one month prior to enrolment
• Are participating in another research study involving any study medication