Estimating Influenza Vaccine Effectiveness Against Laboratory-Confirmed Influenza Using Linked Public Health...

Area of Science:

• Public Health Surveillance
• Epidemiology
• Immunization Research

Background:

• Mandatory reporting of influenza lab results and vaccinations in California enables vaccine effectiveness (VE) estimation.
• Public health surveillance systems are crucial for monitoring infectious diseases.

Purpose of the Study:

• To assess the seasonal influenza vaccine effectiveness (VE) for the 2023-24 season in California.
• To demonstrate the feasibility of using linked immunization and laboratory data for VE assessment.

Main Methods:

• Analysis of linked influenza immunization registry and laboratory data for California residents (≥6 months) during the 2023-24 season.
• Logistic regression used to calculate adjusted Odds Ratios (OR) comparing vaccination status between influenza-positive and negative cases.
• Vaccine effectiveness calculated as (1 - adjusted OR) x 100, controlling for age, race, ethnicity, specimen collection week, and county.

Main Results:

• Overall VE against laboratory-confirmed influenza was 41% (95% CI, 40%-42%).
• Specific VE estimates: 32% for influenza A, 68% for influenza B.
• VE was lower in adults aged ≥65 years at 26% (95% CI, 24%-29%).

Conclusions:

• Influenza vaccination demonstrated effectiveness in preventing laboratory-confirmed influenza.
• Linked public health surveillance data provide a feasible method for real-time VE monitoring.