There is uncertainty about whether a live attenuated vaccine (LAIV) offers additional benefit over inactivated trivalent influenza vaccine (TIV) in providing indirect benefit to those who are unvaccinated through herd immunity. The goal of this randomized clinical trial is to determine whether immunizing children in Hutterite colonies with LAIV can provide increased community-wide protection over TIV. Children aged 3 to 15 years in Hutterite colonies from Alberta and Saskatchewan will be randomized to one of two regimens: TIV or LAIV. The primary outcome of this study will be laboratory-confirmed influenza as detected by PCR in all participants (i.e vaccine recipients and nonrecipients). Secondary outcomes will include influenza-like illness, hospitalization, pneumonia, death, antibiotic use, absenteeism.

The goal of this study is to test whether immunizing children in Hutterite colonies with LAIV can significantly reduce laboratory-confirmed influenza in the entire community compared to TIV. We hypothesize that ≥70% uptake of LAIV compared to a similar uptake of TIV among healthy children and adolescents will reduce laboratory-confirmed influenza in LAIV colonies by 50% compared to TIV colonies. Other specific objectives are to determine if LAIV reduces influenza in the healthy children and adolescents immunized and if LAIV reduces the following relative to TIV in all participants: influenza-like illness, antimicrobial prescriptions, physician-diagnosed otitis media, school or work-related absenteeism, physician visits for respiratory illness, lower respiratory infection, pneumonia, hospitalizations, and death. We will assess reactogenicity in both study groups.

Group A:

Inclusion criteria:

• healthy children and adolescents aged 36 months to 15 years who will be immunized as part of the intervention.

Exclusion criteria:

1. anaphylactic reaction to a previous dose of LAIV or TIV
2. known IgE-mediated hypersensitivity to eggs manifested as hives, swelling of the mouth and throat, difficulty in breathing, hypotension, or shock
3. history of asthma
4. medically diagnosed or treated wheezing within 42 days before enrollment
5. Guillain-Barré syndrome within eight weeks of a previous influenza vaccine
6. anaphylactic reaction to gentamicin
7. anaphylactic reaction to gelatin
8. anaphylactic reaction to neomycin
9. anaphylactic reaction to arginine
10. pregnancy
11. household contact who is severely immunocompromised being cared for in a protective environment (i.e hematopoietic stem cell transplant)
12. use of aspirin or salicylate-containing products within 30 days before enrollment.

Group B:

Inclusion Criteria

• other Hutterite community members that are not in Group A

Exclusion Criteria:

• there are no exclusion criteria for this category of participants