Moderate influenza vaccine effectiveness in Victoria, Australia, 2011

Area of Science:

• * Public Health
• * Epidemiology
• * Immunology

Background:

• * Influenza surveillance is crucial for monitoring disease burden and vaccine effectiveness.
• * Sentinel general practitioner (GP) networks provide valuable real-time data for public health.
• * Estimating vaccine effectiveness (VE) helps inform vaccination strategies.

Purpose of the Study:

• * To estimate the effectiveness of the seasonal trivalent influenza vaccine in Victoria, Australia, in 2011.
• * To utilize a test-negative case-control design for robust VE estimation.
• * To analyze VE across different influenza virus types, subtypes, and age groups.

Main Methods:

• * A sentinel GP network in Victoria, Australia, conducted surveillance for laboratory-confirmed influenza.
• * A test-negative case-control study design was employed, comparing influenza-positive cases with influenza-negative controls.
• * Vaccine effectiveness was calculated using adjusted odds ratios: VE = (1 - adjusted odds ratio) x 100%.

Main Results:

• * A total of 529 patients were included; 29% tested positive for influenza.
• * Twelve percent of participants were vaccinated; 6% of cases and 15% of controls.
• * Adjusted VE against all influenza was 56%, but this finding was not statistically significant.

Conclusions:

• * The estimated influenza vaccine effectiveness was 56%, suggesting potential protection, although not statistically significant in this study.
• * VE estimates showed consistency across different influenza virus types and subtypes, indicating a good match with vaccine strains.
• * Higher VE was observed in working-age adults compared to children, suggesting age-related differences in vaccine response.