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Live attenuated influenza vaccine (LAIV): recent effectiveness results from the USA and implications for LAIV
Richard Pebody1, Jim McMenamin2, Hanna Nohynek3
1Respiratory Diseases Department, National Infection Service, Public Health England, London, UK.
Insights
Live attenuated influenza vaccine (LAIV) showed significant effectiveness in UK and Finnish children, contrasting with US findings. Ongoing monitoring is crucial for understanding LAIV performance in pediatric influenza vaccination programs.
Area of Science:
- Pediatric infectious diseases
- Vaccinology
- Public health
Background:
- The USA has a long-standing pediatric influenza vaccination program utilizing live attenuated influenza vaccine (LAIV).
- Following concerns about LAIV's vaccine effectiveness (VE) in the 2015/2016 season, particularly against influenza A(H1N1)pdm09, the USA suspended its use for 2016/2017.
- The UK and Finland introduced LAIV for children in 2013/2014 and 2015/2016, respectively, initiating close program monitoring.
Purpose of the Study:
- To compare the vaccine effectiveness (VE) of live attenuated influenza vaccine (LAIV) in pediatric populations across different countries.
- To investigate the reasons behind observed variations in LAIV VE, especially concerning specific influenza strains like A(H1N1)pdm09.
- To inform ongoing recommendations and monitoring strategies for childhood influenza vaccination programs.
Main Methods:
- Comparative analysis of vaccine effectiveness (VE) data from national influenza surveillance programs in the USA, UK, and Finland.
- Monitoring of laboratory-confirmed influenza cases in children participating in vaccination programs.
- Review of studies reporting VE of LAIV compared to inactivated influenza vaccines.
Main Results:
- In the 2015/2016 season, the UK and Finland reported significant VE for LAIV against laboratory-confirmed influenza in children, unlike the USA.
- Several studies indicated lower VE for LAIV against A(H1N1)pdm09 compared to inactivated influenza vaccines, though not for A(H3N2) or B strains.
- The underlying reasons for these VE discrepancies are still under investigation.
Conclusions:
- Despite differing results, both the UK and Finland continue to recommend LAIV for children in their 2017/2018 vaccination programs.
- Enhanced monitoring of pediatric influenza vaccination programs is essential to assess LAIV performance across various outcomes and influenza strains.
- Further research is needed to elucidate the factors influencing LAIV effectiveness in different settings and against specific influenza virus subtypes.
Abstract:
The USA has a long-standing paediatric influenza vaccination programme, including use of live attenuated influenza vaccine (LAIV). Following US evidence of apparent lack of vaccine effectiveness (VE) of LAIV in 2015/2016, particularly against A(H1N1)pdm09, the USA suspended the use of LAIV in the 2016/2017 season. The UK introduced LAIV for children in 2013/2014 and Finland in 2015/2016. Both countries have since been closely monitoring programme performance. In 2015/2016, the UK and Finland, unlike the USA, found evidence of significant VE of LAIV against laboratory-confirmed influenza. Several studies, however, reported relatively lower VE of LAIV against A(H1N1)pdm09 infection compared with inactivated influenza vaccine, although not for A(H3N2) or B. The reasons for these apparent differences remain under investigation. Both the UK and Finland continue to recommend the use of LAIV in children for the 2017/2018 season and are intensifying further monitoring of their childhood programmes against a range of end-points.
