Cost of shingles: population based burden of disease analysis of herpes zoster and postherpetic neuralgia

Abstract

Background: Around 30% of the population will experience herpes zoster (HZ), 10% of whom develop postherpetic neuralgia (PHN). Together, these illnesses produce a significant economic burden to the healthcare system.

Methods: Administrative healthcare data collected over the period of April 1^st 1997 to March 31^st 2014 were analyzed to determine the healthcare system burden of HZ using direct medical costs. Episodes of HZ were identified using international classification of disease (ICD) codes. Trends in age-adjusted (AA) HZ-rates were analyzed by piecewise-regression. Total annual and per-episode costs were determined for drug treatment, medical care, and hospitalizations within each year.

Results: The incidence of HZ increased by 49.5% from 1997/98 to 2013/14. Piecewise-regression of AA-rates revealed a steady AA-rate of 4.7 episodes/1000 person-years (PY) from 1997/98 to a breakpoint in 2008/09, after which rates began to increase reaching 5.7 episodes/1000 PY in 2013/14. Drug costs rose significantly (p <0.03) from $89.77/episode (95% CI: $82.96, $96.59) to $127.34/episode (95% CI: $117.24, $137.44). Medical costs increased (p <0.0001) from $57.98/episode (95% CI; $55.26, $60.70) to $78.84/episode (95% CI; $74.08, $83.61). Hospitalization rates declined from 3.10% in 1997/98 to 1.36% in 2011/12, resulting in cost dropping from $397/episode (95% CI; $284, $511) to $195/episode (95% CI; $129, $260). Total annual costs of HZ and PHN were $1,997,183 in 2011/12, 4.7% lower than the 1997/98 costs of $2,095,633.

Conclusion: A significant increase in annual number of HZ cases was observed, driven largely by demographic factors. A 21% increase in the AA-incidence reveals changes in HZ rates beyond those expected by population shifts. The large increase in incidence of HZ, with rising per episode medical and prescription costs were offset by dramatic drops in hospitalization rates, the net effect of which has been to hold the total costs relatively constant. However, the decrease in hospitalization rates slowed over the last half of the study, settling at 1.3% in the last 4 study years. The likely future of HZ burden is one of rising costs, primarily driven by the demographic shifts of an increasing and aging population.

Keywords: Administrative data; Burden; Economics; Epidemiology; Herpes zoster; Postherpetic neuralgia.

Fig. 1

Piecewise regression on age adjusted incidence of herpes zoster. The age adjusted incidence of herpes zoster was calculated using 1997 as the reference year for age standardization. A highly significant breakpoint was found in July 2009 (p < 0.0001). Varicella zoster vaccinations were added to the routine childhood vaccination schedule in 2004. Abbreviations: VZV, varicella zoster vaccinations; BP, breakpoint; HZ, herpes zoster; CI, confidence interval

Fig. 2

Cost per episode of herpes zoster by treatment modality. The mean cost of treating herpes zoster was determined within each year and regression analysis performed (solid lines). Significant trends were found for all modalities: prescription and medical costs p < 0.0001; hospitalization p < 0.0002. All costs have been adjusted to 2013 Canadian dollars using Statistics Canada consumer price index

Fig. 3

Overall Burden of Herpes Zoster: 1997/98 to 2011/12. The total economic and epidemiologic burden of herpes zoster was determined for the period from 1997/98 to 2011/12 and are shown in the above figure. The inner circle shows the number of episodes broken down by post-herpetic neuralgia (PHN) status, with the orange portion representing episodes in which it occurred, while the outer ring breaks down the total costs in 2013 Canadian dollars. While PHN accounted for less than 10% of all episodes, it was responsible for 35% of total costs