Guest blog by Gemma Shields

It is common knowledge that people aged over 65 are encouraged to have a seasonal flu vaccine and each year approximately 70% do (PHE 2018). The burden of influenza in this population is great; with the majority of influenza-attributable deaths occurring in this group (Cromer 2014). Influenza exacerbates existing chronic conditions that are often more common in older people, such as respiratory problems, and causes secondary infections. Unfortunately, as people age, the immune system can become compromised and less responsive to vaccination (Haq 2014).

Last year, I worked on a systematic review of economic evaluations of seasonal influenza vaccination for the population aged over 65 (Shields 2017). Of the eight studies identified, results were generally favourable and suggested cost-effectiveness. However, studies were limited by uncertainty within the data, predominantly due to inadequate evidence on the efficacy of vaccination in this population and variations across flu seasons.

The International Longevity Centre – UK recently published a new report entitled “An Economic Analysis of Flu Vaccination”; presenting a new economic model assessing the costs and benefits of flu vaccination in England.

In scenarios one and two, using actual data from flu seasons, total incremental costs were estimated at £93 and £33 million annually respectively (including cost offsets generated from vaccination), with 277 and 4,021 deaths averted in each scenario. Using these figures, the incremental cost per death averted can be calculated as £336,366 or £8,455 depending on the scenario; demonstrating vastly different results across seasons. In the third scenario, an ideal situation with higher coverage rates and improved efficacy in the over 65s results in influenza vaccination becoming dominant (both cost saving and health improving).

The use of three scenarios with differing vaccine coverage and efficacy rates helps to clearly demonstrate uncertainty between flu seasons and highlights how crucial, as would be expected, vaccination efficacy is.

For me, the work raises three key questions:

1. Given that the vaccination efficacy rate in older people is key, can efficacy be improved in this group?
2. If improving vaccination efficacy in the over 65s is not an option, could benefits be accrued by focusing on increasing coverage in other groups? Note this has been discussed in the recent literature (Fisman 2017). A more complex economic model design could capture the impact of transmission across the population and herd immunity benefits if data was available to inform this.
3. Can we be confident that current data captures all potential benefits in the over 65 population and if not, are analyses underestimating potential health gains? Flu may aggravate existing conditions (e.g. respiratory conditions) and may not be recorded as the primary diagnosis in morbidity and mortality data.

Seasonal influenza continues to place a large burden on the population and healthcare system each year and vaccination, whilst relatively cheap per patient, amounts to substantial costs at a population level.  Therefore, it is good to see further economic evaluations being developed in this area, especially one that considers a range of scenarios utilising recent data from flu seasons. This evaluation demonstrates that further work to improve the efficacy of the flu vaccine (particularly in over 65s), and robust data, are needed to reduce uncertainty and increase the likelihood of flu vaccines being a cost-effective intervention. When more robust data is available to inform economic models, more complex model designs can be used to assess whether changes in policy (e.g. targeted uptake in younger populations), could be more cost-effective in preventing influenza in the over 65s and other population groups.

Click here to read ILC’s An Economic Analysis of Flu Vaccination.

References

Cromer D, van Hoek AJ, Jit M, Edmunds WJ, Fleming D, Miller E. The burden ofinfluenza in England by age and clinical risk group: a statistical analysis to inform vaccine policy. J Infect. 2014 Apr;68(4):363-71.

Fisman DN, Bogoch II. Have you herd? Indirect flu vaccine effects are critically important. Lancet Public Health. 2017 Feb;2(2):e57-e58.

Haq K, McElhaney JE. Immunosenescence: Influenza vaccination and the elderly. Curr Opin Immunol. 2014 Aug;29:38-42. doi: 10.1016/j.coi.2014.03.008.

Public Health England. Seasonal influenza vaccine uptake in GP patients: winter season 2017 to 2018. Final data for 1 September 2017 to 31 January 2018. Available at: https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/710416/Seasonal_influenza_vaccine_uptake_in_GP_patients_winter_season_2017_to_2018..pdf

Shields GE, Elvidge J, Davies LM. A systematic review of economic evaluations of seasonal influenza vaccination for the elderly population in the European

Union. BMJ Open. 2017 Jun 10;7(6):e014847.  Haq K, McElhaney JE. Immunosenescence: Influenza vaccination and the elderly. Curr Opin Immunol. 2014 Aug;29:38-42.