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This is a plain English summary of an original research article. The views expressed are those of the author(s) and reviewer(s) at the time of publication.
Flu vaccination helps prevent some deaths, serious strokes, heart failure and pneumonia in people with type 2 diabetes. Vaccination is linked to less hospital admissions for these reasons, but there is no link to rates of admissions for heart attack.
The results come from a reliable population-based study that looked back at the general practice and hospital records of almost 125,000 adults with type 2 diabetes in England. Outcome rates were compared between those who had and hadn’t received the flu vaccine over seven successive flu seasons. The researchers carefully adjusted for things like the seasonal change in flu numbers.
The findings strongly support current recommendations that people with chronic medical conditions such as diabetes receive the annual flu vaccine. However, flu remains a substantial health burden, and the uptake of vaccination is still poor in some areas.
The finding that deaths are prevented for people with type 2 diabetes, might be a further stimulus to better ensure that those at risk are covered by vaccination.
Why was this study needed?
Each winter, tens of thousands of people are hospitalised because of flu. Around 8,000 people each year die from flu in England, and it is estimated that in people with diabetes the death rate from flu is 2.2 per 100,000 people.
Having a long-term condition such as diabetes can make the effects of the flu worse, even if the condition is well managed.
This study was commissioned because, despite the recommendation for people with a chronic medical condition such as diabetes to have the annual flu vaccination, it was unknown with any certainty what the outcomes were.
What did this study do?
This retrospective cohort study included 124,503 adults with type 2 diabetes. These people were identified from a UK general practice database (Clinical Practice Research Datalink) between 2003/04 and 2009/10. Researchers looked at the rate of uptake of the seasonal flu vaccine each year, which ranged from 63.1% to 69.0%.
The database was linked with national hospital admissions and death rate statistics. The main outcomes of interest were hospital admissions for heart attack, stroke, pneumonia, flu, heart failure and death from any cause.
The rate of these outcomes was compared for people who had and hadn’t had the flu vaccine. Analyses took into account flu activity in any season (number of GP consultations for flu per week), and participants’ age, health and lifestyle characteristics.
Although this study looked back at records this was a large study and the authors adjusted for the seasonal effects and other factors that could have spuriously led to increases in the effect. Carefully matching people in the registry, for example to remove this confounding. This means that it provides reliable information of what happens in UK practice in an area where randomisation is unlikely to be ethical, and this will probably be the best study design possible.
What did it find?
- Flu vaccination was associated with 24% lower rates of death from any cause (IRR 0.76, 95% CI 0.65 to 0.83).
- It was also associated with significantly lower rates of hospital admissions for stroke, reduced by 30% (incidence rate ratio [IRR] 0.70, 95% confidence interval [CI] 0.53 to 0.91), heart failure by 22% (IRR 0.78, 95% CI 0.65 to 0.92), and pneumonia or flu by 15% (IRR 0.85, 95% CI 0.74 to 0.99).
- Flu vaccination wasn’t associated with fewer hospital admissions for heart attack (IRR 0.62, 95% CI 0.62 to 1.04).
What does current guidance say on this issue?
A flu vaccine is available for free on the NHS for adults aged 65 and over, pregnant women, some children, and other groups at risk including those with chronic medical conditions such as diabetes. This is as part of the national flu programme run by Public Health England and delivered by NHS England.
To improve uptake of flu vaccination, the Joint Committee for Vaccination and Immunisation recommends that GP surgeries have a named person responsible for the flu vaccination programme, identify people at high risk from flu, maintain a register of those eligible, and invite them for vaccination.
What are the implications?
This study provides evidence that flu vaccination for people with type 2 diabetes reduces hospital admission rates for certain cardiovascular and respiratory diseases, as well as lowering death rates.
The study included a large population, but the 300 general practices covered by the database only cover 5% of England’s population. Therefore, it can’t be ensured that the findings are nationally representative. Neither can this type of study prove cause and effect.
However, the findings suggest that people with diabetes are a group at increased risk from flu complications. Current guidance recommends that GP surgeries identify people most at risk from flu and invite them to receive flu vaccination.
It is likely that this new knowledge about the survival benefits of flu vaccination for people with diabetes will provide further justification for efforts to increase the uptake of flu vaccination.
Citation and Funding
Vamos EP, Pape UJ, Curcin V, et al. Effectiveness of the influenza vaccine in preventing admission to hospital and death in people with type 2 diabetes. CMAJ. 2016;188(14):E342-351.
The Department of Primary Care and Public Health at Imperial College is grateful for support from the National Institute of Health Research (NIHR) North West London Collaboration for Leadership in Applied Health Research and Care scheme, the NIHR Biomedical Research Centre scheme and the Imperial Centre for Patient Safety and Service Quality.
Bibliography
JCVI. Chapter 19. Influenza. In: The Green Book (Immunisation against infectious disease). Joint Committee on Vaccination and Immunisation; 2015.
PHE. The flu vaccination: Winter 2016/17. London. Public Health England; 2016.
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