Live Attenuated and Inactivated Influenza Vaccine Effectiveness

Area of Science:

• Pediatric Infectious Diseases
• Vaccinology
• Epidemiology

Background:

• Observational studies on vaccine effectiveness (VE) comparing quadrivalent live attenuated vaccine (LAIV4) and inactivated influenza vaccine (IIV) in children and adolescents yielded inconsistent results.
• Previous studies were limited by small sample sizes, necessitating larger pooled analyses.

Purpose of the Study:

• To compare the VE of LAIV4 and IIV against medically attended, laboratory-confirmed influenza in children and adolescents (2-17 years).
• To analyze VE by influenza season, subtype, age group, and prior vaccination status using pooled data from five US studies (2013-2016).

Main Methods:

• Pooled individual patient-level data from five US observational studies (2013-2014 to 2015-2016).
• Compared VE of LAIV4 and IIV in 17,173 patients aged 2-17 years.
• Calculated VE using adjusted logistic regression models (100% × (1 - odds ratio)).

Main Results:

• Inactivated influenza vaccine (IIV) demonstrated 67% VE against influenza A/H1N1pdm09, while LAIV4 showed 20% VE.
• LAIV4 recipients had significantly higher odds of influenza A/H1N1pdm09 infection compared to IIV recipients (OR 2.66).
• LAIV4 and IIV exhibited similar effectiveness against influenza A/H3N2 and B strains.

Conclusions:

• Pooled analysis revealed reduced effectiveness of LAIV4 compared to IIV against influenza A/H1N1pdm09.
• Findings align with previously published individual study results, highlighting a specific VE difference between vaccine types for certain influenza strains.