Asymptomatic Flu Project (AFP)

December 13, 2025 updated by: Hospices Civils de Lyon

Incidence of Symptomatic and Asymptomatic Influenza Among Healthcare Workers : A Multicenter Cohort Study

Although clinical presentation of influenza is often symptomatic, asymptomatic cases also occur. The knowledge of the incidence of asymptomatic influenza among healthcare workers is very important because of the risk of cross-transmission to hospitalized patients. The principal objective of the study is to estimate the incidence of symptomatic and asymptomatic influenza among healthcare workers in short-stay wards. The results of this study will lead to a better understanding of the burden of asymptomatic influenza among healthcare workers and might be used as an argument to increase influenza vaccine coverage among healthcare workers.

Study Overview

Status

Completed

Conditions

Intervention / Treatment

Study Type

Interventional

Enrollment (Actual)

289

Phase

  • Not Applicable

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Locations

  • France
      • Lyon, France, 69437
        • Edouard Herriot Hospital; Department of Epidemiology, Hygiene and Public Health

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

18 years and older (Adult, Older Adult)

Accepts Healthy Volunteers

Yes

Description

Inclusion Criteria:

  • Volunteer health-care workers
  • Working in the following wards: short-stay, inpatient (including ICU) and emergency

Exclusion Criteria:

  • Presence of influenza symptoms at enrolment
  • Programmed absence (maternity leave, vacation, etc.)
  • Administrative agents

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Prevention
  • Allocation: N/A
  • Interventional Model: Single Group Assignment
  • Masking: None (Open Label)

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Experimental: Health-care workers
Health-care workers recruited in the study will have blood sampling and naso-pharyngeal bottle-brush sampling
Biological: Blood sampling
Other: Nasal swab

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Incidence of influenza cases
Time Frame: 6 months after inclusion
Incidence of asymptomatic and symptomatic influenza per 1000 days at risk among healthcare workers
6 months after inclusion

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Fraction of asymptomatic influenza cases
Time Frame: 6 months after inclusion
Fraction of asymptomatic influenza cases among patients with confirmed influenza infection (seroconversion)
6 months after inclusion
Stratified incidence ratios
Time Frame: 6 months after inclusion
The objective is to compare the proportion of asymptomatic influenza among vaccinated and unvaccinated healthcare workers, stratified on the type of influenza virus , gender, age, and other covariates
6 months after inclusion
Incidence of influenza-like illness
Time Frame: 6 months after inclusion
The objective is to calculate the incidence of influenza-like illness without virological confirmation
6 months after inclusion
proportion of health-care workers with Influenza vaccine coverage
Time Frame: 6 months after inclusion
The objective is to estimate the vaccination coverage against influenza among health care workers
6 months after inclusion
Number of sick-leave days per participating ward
Time Frame: 6 months after inclusion
The objective is to estimate the professional impact of influenza in a population of healthcare workers
6 months after inclusion

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Hospices Civils de Lyon

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

October 4, 2016

Primary Completion (Actual)

March 21, 2017

Study Completion (Actual)

March 21, 2017

Study Registration Dates

First Submitted

August 11, 2016

First Submitted That Met QC Criteria

August 11, 2016

First Posted (Estimated)

August 16, 2016

Study Record Updates

Last Update Posted (Estimated)

December 19, 2025

Last Update Submitted That Met QC Criteria

December 13, 2025

Last Verified

December 1, 2025

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • 69HCL16_0095

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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