Diabetes is a disease with high prevalence, with an estimated 59.8 million cases in Europe in 2015.¹ In Ireland the reported age-adjusted prevalence rate of diabetes, including type 1, type 2 and gestational diabetes for 2015, is 4.4% (3.4-6.0) equating to 135-223 cases per 1,000 adults aged between 20 and 79 years.¹

Among the medical sequelae of diabetes is a reduced ability to fight off infection. People with diabetes are at considerably greater risk from the consequences of influenza or pneumococcal disease. It has been estimated that diabetes patients are six times more likely to be hospitalised with a diagnosis of influenza compared with age and sex-matched controls.²

Diabetes is also one of the three most common risk factors for pneumococcal bacteraemia,² and rates of invasive pneumococcal disease are increased in diabetes patients, with higher treatment costs compared to those of healthy individuals.³ Because of these risks, all people with diabetes are recommended to receive both the seasonal influenza vaccination and pneumococcal vaccination.

Irish immunisation guidelines

Irish immunisation guidelines advise annual vaccination with the influenza vaccine for all those with diabetes, while pneumococcal vaccination is advised for those under 65 years of age and with a risk condition (including diabetes) or at age 65 without such a risk condition.⁴ Booster donation is indicated five years after the first dose if that was delivered under the age of 65, and in those who received the first dose aged over 65 with a risk condition.⁴

The Council of the European Union and the World Health Organization have recommended target vaccination rates of 75% for influenza with preferably higher rates in risk groups.^5,6 Despite these recommendations, the uptake of the influenza vaccine during the 2009/2010 season among diabetes patients in Ireland has recently been reported at 64.5% out of 200 patients attending a diabetes outpatient clinic, while in the same group, lifetime pneumococcal vaccination was 22%.⁷

In this study, we quantify the rates of influenza and pneumococcal vaccination among patients attending a primary care centre in the west of Ireland and investigate demographic and clinical factors associated with vaccine status.

Methods

Study population

This study was conducted at an urban-based primary care practice located in Galway city, serving several thousand patients, with 176 diabetes patients registered with the practice. 

This study was primarily based on a medical record review using the practices case management software, Socrates, to identify the diabetes patients of the practice. The search criteria included all patients with type 1 and type 2 diabetes as well as pregnant women with gestational diabetes. 

The immunisation status of each patient was then recorded along with his or her gender, age, type of diabetes and duration of diabetes since diagnosis. For influenza vaccination status, searches on the patients file were conducted from September 1, 2016 to January 9, 2017. For pneumococcal vaccination status, the patient’s complete medical history was searched. 

Statistical analysis

Data were anonymised and descriptive statistics of demographic and clinical characteristics of the participants were performed. 

Descriptive statistics

One hundred and seventy-six patients with diabetes were identified. Of those, 15% (n = 27) had type 1 diabetes and 84% (n = 149) had type 2 diabetes. Only one participant had gestational diabetes. The study population had an overall mean age of 53.0 years (95% CI: 50.4-55.5) and disease duration of 8.1 years (95% CI: 7.2-9.0). Table 1 details descriptive statistics of the study population stratified by gender. There was no missing data.

Of the total study population 15.3% (27/176) were completely up-to-date with their vaccinations having received both their annual influenza vaccination (during the 2016/17 flu season) and their pneumococcal vaccination, which was in date. Sixty-two (35.2%) of the study population had received their annual influenza vaccination and 39 (22.1%) had received a pneumococcal vaccination that was in-date, while 56 (31.7%) had lifetime uptake of the pneumococcal vaccine; 102 (57.9%) of the study population had received neither their annual influenza vaccination nor a pneumococcal vaccination.

Table 2 summarises age and disease duration stratified by diabetes type and by disease duration. Among type 1 patients, increased age was significantly associated with a higher vaccination rate for influenza only, while among type 2 patients, increased age was significantly associated with higher vaccination rates for each vaccine. 

Disease duration and gender were not associated with vaccination rates for either disease sub-type. Among over 65s (regardless of disease sub-type), 52% had current influenza vaccination status and 36% had current pneumococcal vaccination status, while 32% were current for both vaccines.

Logistic regression models

Univariate odds ratios (ORs) for vaccination are also shown in Table 2. For the influenza vaccine each year increase in age was associated with a 1.01 (95% CI: 1.00-1.02 ) increase in ORs for type 1 and type 2 diabetes, while for the pneumococcal this was true only for type 2 diabetes.

We did not model pneumococcal vaccination for type 1 patients due to only two patients in this category receiving the vaccine. For the influenza vaccine in type 1 diabetes patients, ORs were virtually unchanged. For type 2 diabeties patients, the age of diagnosis remained significant for both vaccines; however, for the pneumococcal vaccine the duration of disease was also statistically significant with OR 1.02 (95%CI: 1.01-1.04,) per year of disease duration.

Results

We found that 35.2% of this primary care population were vaccinated with the current influenza vaccine. This rate of influenza vaccination is significantly lower than the 64.5% reported by an Irish diabetes outpatients clinic report⁷ which aimed to determine pneumococcal vaccine uptake over a lifetime, and to identify predictors that may influence likelihood of vaccine uptake. 

In a large study (n = 867,683) of the German population influenza vaccine uptake among those at medium risk (the category including diabetes) 56.8% were vaccinated for influenza and 16.0% were vaccinated for pneumococcus.⁸ Of 3,443 type 2 diabetes patients in the Madrid area, 65.7% received influenza vaccination in 2013.⁹

We found 31.7% with lifetime uptake of the pneumococcal vaccine which compares favourably to 22% in the Irish diabetes outpatients clinic report.⁷ It also compares favourably to an outpatient study of 219 diabetes patients in Poland where 26.5% had current influenza vaccinations and 9.1% had lifetime uptake of the pneumococcus vaccine. Nevertheless, the vaccination rates we found fall short of the 75% target rate advised by the WHO for influenza.⁵

In keeping with findings by others, we found that increased vaccination rates are associated with older age.^2,7,8 Vaccine rates were more than doubled in over 65s versus under 65s for the group as a whole. While this would be expected in a non-diabetes cohort, this suggests that more needs to be done to raise awareness of vaccine guidelines among younger diabetes patients and healthcare staff. 

We also found after multivariate regression that longer disease duration was associated with higher pneuomococcal vaccine uptake in patients with type 2 diabetes. This is unlikely to be explained by an association between disease duration and age as this relationship was not apparent before correction for variables, including age.

Discussion

These results suggest that more needs to be done to improve vaccine uptake among diabetes patients. Clancy et al noted previously that a simple recommendation from a GP could notably increase vaccine uptake.⁷

In a study of 795 GP practices across the UK, Dexter et al found that appointing a lead member of staff to be responsible for arranging and managing the practice’s influenza vaccination campaign and for the production of a written report reviewing vaccination rates was shown to be associated with increased vaccination uptake.¹⁰

Additionally, they found that in those over 65 years of age, further factors including sending personal invitations to patients, such as a letter or an automatically generated text message, was associated with significantly higher rates of vaccination.¹⁰ These measures, coupled with other strategies were found to boost vaccine uptake rates by 7%-8% in patients aged over 65 years.¹⁰

Strengths and weaknesses of the study

An important strength of this study is the completeness of the data. The data was obtained from searches on the practices case management system Socrates. The practice has used Socrates for a number of years and all members of the practice use the software consistently and every effort is made to ensure that patient data is up-to-date and correct. This enabled us to capture complete data for the study participants. 

A limitation of the study is the fact that a number of patients in the study population may have been vaccinated outside of the practice. Pharmacies are licensed to administer the influenza vaccine and it is possible that at least a few patients may have availed of this service. This will not have been recorded in the patients’ files. As a consequence, the figures quoted in the audit for influenza vaccination uptake at least, may be artificially low. 

Conclusions

In summary, this study demonstrated that, among diabetes patients of a primary care practice, the uptake of influenza vaccination was below those of other European countries, but the rate for pneumococcal vaccinations compared favourably. However, vaccination rates were significantly below recommended levels. 

Older age was associated with increased influenza and pneumococcal vaccination rates, while longer disease duration was associated with increased pneumococcal vaccination rates in type 2 diabetes patients. 

References

1. International Diabetes Federation. IDF Diabetes Atlas Seventh Edition 2015. http://www.oedg.at/pdf/1606_IDF_Atlas_2015_UK.pdf. Accessed May 10 2017
2. Wahid ST, Nag S, Bilous RW, Marshall SM, Robinson ACJ. Audit of influenza and pneumococcal vaccination uptake in diabetic patients attending secondary care in the Northern Region. Diabet Med. 2001;18(7): 599-603
3. Weycker D, Farkouh RA, Strutton DR, Edelsberg J, Shea KM, Pelton SI. Rates and costs of invasive pneumococcal disease and pneumonia in persons with underlying medical conditions. BMC Health Serv Res  2016;16(1):182. doi: 10.1186/s12913-016-1432-4
4. Health Services Executive. Immunisation Guidelines for Ireland. www.hse.ie/eng/health/Immunisation/hcpinfo/guidelines/. Accessed January 21 2017.
5. World Health Organization. Prevention and control of influenza pandemics and annual epidemics. 2003;(May). http://www.who.int/immunization/sage/1_WHA56_19_Prevention_and_control_of_influenza_pandemics.pdf. Accessed January 23 2017
6. Council of the European Union. Council Recommendation of 22 December 2009 on seasonal influenza vaccination. Off J Eur Union. 2009;L348(1019):0071-2
7. Clancy U, Moran I, Tuthill A. Prevalence and predictors of influenza and pneumococcal vaccine uptake in patients with diabetes. Ir Med J. 2012; 105(9): 298-300 
8. Theidel U, Kuhlmann A, Braem A. Pneumococcal vaccination rates in adults in Germany: an analysis of statutory health insurance data on more than 850,000 individuals. Dtsch Arztebl Int. 2013;110(44):743–50. doi:10.3238/arztebl.2013.0743
9. Jiménez-Garcia R, Lopez-de-Andres A, Hernandez-Barrera V, et al. Influenza vaccination in people with type 2 diabetes, coverage, predictors of uptake, and perceptions. Result of the MADIABETES cohort a 7 years follow up study. Vaccine. 2017;35(1):101-8. doi: 10.1016/j.vaccine.2016.11.039
10. Dexter LJ, Teare MD, Dexter M, Siriwardena N, Read RC. Strategies to increase influenza vaccination rates: outcomes of a nationwide cross-sectional survey of UK general practice. BMJ Open. 2012;2(3):e000851. doi:10.1136/bmjopen-2011-000851