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Live-Attenuated Influenza Vaccine Effectiveness in Children From 2009 to 2015-2016: A Systematic Review and
Herve Caspard1, Raburn M Mallory1, Jing Yu1
1MedImmune, Gaithersburg, Maryland.
Insights
Live-attenuated influenza vaccine (LAIV) showed consistent effectiveness against influenza B strains and matched A(H3N2) strains. However, LAIV was less effective than inactivated influenza vaccine (IIV) against A(H1N1)pdm09 strains.
Area of Science:
- Virology
- Immunology
- Public Health
Background:
- Live-attenuated influenza vaccine (LAIV) effectiveness since the 2009 pandemic requires evaluation.
- Children and young adults are key populations for influenza vaccination strategies.
Purpose of the Study:
- To systematically review and consolidate LAIV effectiveness data against laboratory-confirmed influenza.
- To analyze LAIV performance by formulation and influenza strain.
Main Methods:
- Systematic literature search of MEDLINE (2010-2016).
- Inclusion of studies reporting LAIV effectiveness estimates against culture- or PCR-confirmed influenza.
- Random-effects meta-analysis of effectiveness estimates categorized by vaccine formulation and strain.
Main Results:
- LAIV demonstrated consistent effectiveness against influenza B and matched A(H3N2) strains.
- LAIV was less effective than inactivated influenza vaccine (IIV) against A(H1N1)pdm09 strains, particularly with monovalent and trivalent formulations.
- Quadrivalent LAIV showed effectiveness but was less effective than IIV against A(H1N1)pdm09; protection against mismatched A(H3N2) was not significant.
Conclusions:
- LAIV effectiveness against A(H1N1)pdm09 strains is lower than IIV.
- Further investigation is needed to understand differences in LAIV effectiveness between pre- and postpandemic A(H1N1) vaccine strains.
- Development of more consistently effective A(H1N1)pdm09 vaccine strains is warranted.
Background:
This systematic review and meta-analysis describes and consolidates findings from all studies that assessed the effectiveness of live-attenuated influenza vaccine (LAIV) against laboratory-confirmed influenza since the 2009 pandemic in children and young adults.
Methods:
A MEDLINE search was conducted for articles published from January 1, 2010 to November 30, 2016. All original publications reporting an effectiveness estimate of LAIV against cases of influenza confirmed by reverse-transcription polymerase chain reaction or culture were retained for analysis. Effectiveness estimates were categorized by LAIV formulation (monovalent, trivalent, and quadrivalent) and strain (any influenza strain, A(H1N1)pdm09, A(H3N2), and B strains). Consolidated estimates were obtained with a random-effects model.
Results:
A total of 24 publications presenting 29 observational studies were retained for meta-analysis. Live-attenuated influenza vaccine was not shown to be effective against A(H1N1)pdm09 strains as a monovalent formulation in 2009-2010 or as a trivalent formulation from 2010-2011 to 2013-2014, but consolidated sample sizes were small. It was effective as a quadrivalent formulation but less effective than inactivated influenza vaccine (IIV). Live-attenuated influenza vaccine was consistently effective against B strains and matched A(H3N2) strains but was not shown to provide significant protection against mismatched A(H3N2) strains in 2014-2015.
Conclusions:
These findings confirm that effectiveness of LAIV against A(H1N1)pdm09 strains has been lower than IIV. A systematic investigation has been initiated to determine the root cause of the difference in effectiveness between pre- and postpandemic A(H1N1) vaccine strains and to identify a more consistently effective A(H1N1)pdm09 vaccine strain.
