Try our beta test site
IMPORTANT: Listing of a study on this site does not reflect endorsement by the National Institutes of Health. Talk with a trusted healthcare professional before volunteering for a study. Read more...

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

This study has been completed.
Research Fund for the Control of Infectious Diseases
The Research Grants Council, Hong Kong
Centre for Health Protection
Information provided by:
The University of Hong Kong Identifier:
First received: November 13, 2008
Last updated: December 29, 2014
Last verified: December 2014
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.

Condition Intervention
Influenza Virus Infection
Biological: Inactivated influenza vaccine
Biological: Saline

Study Type: Interventional
Study Design: Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: Double Blind (Participant, Care Provider, Outcomes Assessor)
Primary Purpose: Prevention
Official Title: A Randomised Controlled Trial of the Effectiveness of Vaccinating Children to Reduce Household Transmission of Influenza

Resource links provided by NLM:

Further study details as provided by The University of Hong Kong:

Primary Outcome Measures:
  • The proportions of subjects and household contacts with serology-confirmed influenza infection during follow-up among the 2 intervention arms. [ Time Frame: nine months ]

Estimated Enrollment: 2800
Study Start Date: September 2008
Study Completion Date: December 2010
Primary Completion Date: December 2010 (Final data collection date for primary outcome measure)
Arms Assigned Interventions
Active Comparator: 1
Influenza vaccine
Biological: Inactivated influenza vaccine
0.5ml intramuscular single dose
Other Name: VAXIGRIP®, Sanofi Pasteur
Placebo Comparator: 2 Biological: Saline
0.5ml intramuscular, one dose

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.


Ages Eligible for Study:   Child, Adult, Senior
Sexes Eligible for Study:   All
Accepts Healthy Volunteers:   Yes

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.
  Contacts and Locations
Choosing to participate in a study is an important personal decision. Talk with your doctor and family members or friends about deciding to join a study. To learn more about this study, you or your doctor may contact the study research staff using the Contacts provided below. For general information, see Learn About Clinical Studies.

Please refer to this study by its identifier: NCT00792051

The University of Hong Kong
Hong Kong, China
Sponsors and Collaborators
The University of Hong Kong
Research Fund for the Control of Infectious Diseases
The Research Grants Council, Hong Kong
Centre for Health Protection
Principal Investigator: Benjamin J Cowling, PhD The University of Hong Kong
  More Information

Publications automatically indexed to this study by Identifier (NCT Number):
Responsible Party: Dr Benjamin John Cowling, The University of Hong Kong Identifier: NCT00792051     History of Changes
Other Study ID Numbers: GML003.4
Study First Received: November 13, 2008
Last Updated: December 29, 2014

Keywords provided by The University of Hong Kong:
Influenza-like illness

Additional relevant MeSH terms:
Influenza, Human
Virus Diseases
Orthomyxoviridae Infections
RNA Virus Infections
Respiratory Tract Infections
Respiratory Tract Diseases
Immunologic Factors
Physiological Effects of Drugs processed this record on May 25, 2017