Cost for physician-diagnosed influenza and influenza-like illnesses on primary care level in Germany – results of a database analysis from May 2010 to April 2012

The current retrospective database analysis describes and quantifies the burden of
seasonal influenza in adults and children at the primary care level in Germany. The
aim of the manuscript was to estimate the annual economic burden of influenza in Germany.
Due to the lack of up to date cost data, we have assessed the resource consumption
related to the treatment of episodes classified as influenza or ILI (ICD-10 J9-J11)
by primary care physicians. The aim was not to evaluate the incidence of confirmed
influenza in Germany. Due to this reason, we have used figures published by RKI to
extrapolate the cost per episode to the economic burden in Germany. Our analysis,
based on a very large sample of patients with clinically diagnosed influenza, showed
that the annual economic burden of seasonal influenza can reach €3.1 billion. Interestingly,
a substantial burden occurs in adults without risk factors for complications and thus
outside the recommended groups for seasonal influenza vaccination.

Our analysis of patients diagnosed with influenza between May 2010 and April 2012
in Germany reveals the monthly distribution of influenza/ILI episodes and accurately
describes the 2010/2011 and 2011/2012 influenza seasons 24], 25]. In the season 2010/2011, the peak of influenza episodes was observed between January
and March. In the following season (2011/2012), the peak occurred between February
and March. However, this was much flatter compared to the 2010/2011 season. Our observations
of monthly influenza/ILI episode distribution correspond to the patterns in reportable
positive influenza diagnoses and practice consultations recorded by the RKI acute
respiratory disease (ARE) monitoring system.

Influenza episodes are frequently accompanied by complications. We observed complications
in 37.4 % of adults and in 53.4 % of children. Three circumstances, however, make
it challenging to compare our findings with the published literature. Firstly, results
often refer only to hospitalized patients; secondly, the types of reported complications
differ; and thirdly, the time period patients are followed-up for varies widely. In
a retrospective US managed care database analysis, complications were documented in
65 % of adults within a 12-month follow-up period 4], as compared to our findings in adults (37.4 %). The difference can be explained
by the large variation in length of follow-up (12 months in the US analysis vs. 1 month
in the present analysis) and the range of investigated complications, which was broader
in the US analysis and included musculoskeletal diseases, diabetes and infectious
diseases in addition to respiratory disorders. In the present analysis, the most frequent
complications in children managed by pediatricians were respiratory tract infections
(20.8 %) and otitis media (13.4 %); this pattern is comparable with published literature
26], 27]. In a review of pediatric influenza managed in the community and primary care in
Western Europe, frequent complications included otitis media (between 0 and 41 %),
bronchitis (between 5 and 10 %), pharyngitis (between 31 and 58 %) and the common
cold (between 15 and 20 %) 26].

Some conditions can put patients at higher risk for developing complications. Overall,
we found the most frequent risk factors for complications to be cardiovascular diseases
in adults (29 %) and respiratory diseases in children (23 %). These are in line with
common risk factors reported in three independent meta-analyses 28]–30]. The first meta-analysis revealed a double risk of developing severe influenza complications
(odds ratio 1.97, 95 % CI 1.06 – 3.67) when patients suffered from cardiovascular
diseases compared to patients without 28]. In the second meta-analysis, cardiovascular diseases accounted for 17.2–20.0 % of
all influenza-related hospitalizations 29], and in the third meta-analysis, influenza vaccination reduced the risk of severe
complications by half (risk ratio 0.57, 95 % CI 0.39 – 0.82) 30]. The authors suggest that in patients with cardiovascular diseases, influenza may
trigger the rupture of a vulnerable atherosclerotic plaque and thus lead to severe
complications 30].

From societal perspective, the cost per episode is substantial. According to the current
analysis, mean total costs in adults are about €514 per influenza episode and about
€105 in children. Overall, the annual economic burden in Germany based on the present
analysis of outpatient EMR data corresponds to the cost dimension published by Szucs
et al. in 2001 3].

The main cost driver in adults is indirect cost because of work days lost. Our findings
are in accordance with the published literature 3], 5]. In adults with high cost episodes ( €1,000), more patients (90 %) were of working
age compared to the total group (79 %) managed by PCPs. In the present analysis, the
mean number of work days lost was 6.0 days in adults with recorded sick notes. This
range is consistent with previous publications where 3.7–5.9 work days per episode
have been reported lost following physician diagnosis of influenza 31].

The costs of seasonal influenza episodes were higher when patients were of working
age and/or had experienced influenza-related complications. In the present analysis,
influenza episodes in the working age group (17–59 years) were associated with mean
total costs 2.4-times higher than those in patients ?60 years. Complications almost
tripled the cost per episode in children and increased the costs by a factor of 1.7
in adults. These findings are in line with results published by Karve et al.4], where healthcare costs among influenza patients with complications were double those
of influenza patients without complications.

In the present analysis, the majority of episodes with complications were reported
in patients without risk factors. Adults without risk factors have traditionally not
been included in influenza vaccination recommendations, which include only nursing-home
residents, elderly individuals, and people at high risk for complications 1]. Consequently, a substantial burden occurs in patients outside the recommended group
for receiving seasonal influenza vaccination. In Germany, healthy working adults have
seasonal vaccination coverage of less than 16 % 32], 33].

If vaccination rates in healthy working adults were increased, the economic burden
due to work days lost could be reduced substantially 34]. Based on a review of economic evaluations of seasonal influenza vaccination in healthy
working age adults in the US, the authors conclude that vaccination does not generally
save costs, but may be economically attractive under certain conditions, such as higher
illness rates, lower costs of vaccination and higher wage rates 35]. To assess, whether vaccination is cost saving for a certain country, an evaluation
based on country-specific epidemiological and health economic data is necessary.

In Germany, influenza vaccine recommendations for adults should be revisited in the
future. The analysis of influenza surveillance by RKI during the 2012/2013 season
showed that absence from work due to influenza reached the highest value for the last
10 years; there were more than 4 million reports of absenteeism 36]. Vaccination in children is widely discussed among clinicians 37] and a recent literature review concluded that vaccination in children, especially
those below 5 years, reduces the influenza-associated disease burden 27]. Such reports emphasize the importance of targeting children and adults in national
immunization policies.

There are limitations to the interpretation of our results. Overall, it has to be
considered that the realization of the actual costs of seasonal influenza is challenged
by the fact that the disease is underreported 38]. On the other hand, with respect to the cost per episode analysed in the present
database analysis, the vast majority of episodes (over 92 %) was classified as “influenza,
virus not identified” (ICD-10 J11). As the aim of the analysis was to describe the
current economic burden, we did also consider the ICD-10 J11 diagnosis when describing
the cost per influenza or ILI episode. Potentially, this introduces an underestimation
of total costs, because ILI episodes might come with a milder course of the disease
with shorter absence from work. Secondly, the total cost per episode is very likely
to be underestimated because of missing information on emergency visits and admissions
at hospitals in the IMS DA database, which is based on EMR data at office-based practices and not linked
to hospital records. Also, information on patient expenses for OTC medication was
not available in the EMR data. Thirdly, an underreporting of parental sick leaves
is very probable. In children, sick certificates were recorded only for 3 episodes
in the current analysis. According to a literature review in Western European countries,
parental absenteeism is common (11–62 %) and lasts on average from 1.3 to 6.3 days
in the parents of children with laboratory-confirmed influenza 26]. Additionally, co-payments were considered for all adult patients and without taking
into account patient groups who do not have to co-pay, like those on chronic medication
or unemployed. This results in a possible slight overestimation of co-payments. Finally,
the extrapolation of cost per episode to annual economic burden of physician-attended
influenza in Germany is a conservative calculation, because it was based on practice
consultations and not on incidence figures. Therefore, an annual economic burden of
up to €3.1 billion could be greatly underestimated.