Direct and Indirect Benefits of Influenza Vaccine Versus Placebo in Healthy Children

Not Applicable

Completed

• Conditions: Influenza Virus Infection
• Interventions: Biological: Inactivated influenza vaccine; Biological: Saline

• Registration Number: NCT00792051
• Lead Sponsor: The University of Hong Kong

Brief Summary

While immunisation of school-age children against influenza is not recommended in Hong Kong, past experience in Japan and elsewhere suggests that immunisation of children may protect the wider community through its indirect transmission-limiting impact as well as the direct immunologic protection afforded vaccinated children themselves. We aim to assess whether vaccinating children against influenza protects vaccinees as well as their household contacts from infection.

Detailed Description

Design and subjects: A double-blind randomised controlled trial of 800 subjects aged 6-17 drawn from the general population and their 2000 household contacts. The subjects will be randomised in a 3:2 ratio to the intervention and placebo groups, respectively. Serum samples will be collected from subjects pre- and 1 month post-vaccination, and after the influenza season. Serum samples will be collected from household contacts at baseline and at the end of the influenza season. During the follow-up period, subjects and household members will keep symptom diaries and those reporting influenza-like-illness will be offered free doctor consultations or home visits where we will arrange for collection of nose and throat swabs.

Study instruments: An antibody titre of ≥40 in the post-vaccine serum will be used to define seroprotection to those particular strains, while a four-fold or higher increase in antibody titres between baseline and end-of-season follow-up of the household contacts will define influenza infection during the season. Subjects and household contacts will be asked to keep symptom diaries, and during episodes of ILI we will collect nose and throat swabs for laboratory confirmation of influenza infection; the primary serology results will then be compared with clinical and laboratory-confirmed influenza episodes.

Interventions: 1 (intervention) inactivated influenza vaccine (Vaxigrip, Sanofi Pasteur); 2 (placebo) saline injection.

Main outcome measures: The proportions of subjects and household contacts with serology-confirmed influenza infection during follow-up among the 2 intervention arms.

Analysis: Intention to treat, adjusting for within-household correlation in influenza attack rates.

Study Timeline

• Study Start: 2008-09
• Study First Submitted: 2008-11-13
• Study First Submitted QC: 2008-11-13
• Study First Posted: 2008-11-17
• Primary Completion: 2010-12
• Study Completion: 2010-12
• Status Verified: 2014-12
• Last Update Submitted: 2014-12-29
• Last Update Posted: 2014-12-30

Recruitment & Eligibility

• Status: COMPLETED
• Sex: All
• Target Recruitment: 2800

Inclusion Criteria

• All vaccinees must be Hong Kong residents aged between 6 and 17.

Exclusion Criteria

• Vaccinees should not be allergic or hypersensitive to the active substances or components (eggs, chicken proteins, formaldehyde, neomycin, etc.) used in the vaccines or where vaccination is otherwise contraindicated. Subjects should not have an underlying immunocompromised condition or be receiving immunosuppressive agents.

Study & Design

• Study Type: INTERVENTIONAL
• Study Design: PARALLEL

Arm && Interventions

Group	Intervention	Description
1	Inactivated influenza vaccine	Influenza vaccine
2	Saline	-

Primary Outcome Measures

Name	Time	Method
The proportions of subjects and household contacts with serology-confirmed influenza infection during follow-up among the 2 intervention arms.	nine months

Trial Locations

Locations (1)

The University of Hong Kong; 🇨🇳 Hong Kong, China