Inequalities in zoster disease burden: a population-based cohort study to identify social determinants using linked data from the U.K. Clinical Practice Research Datalink

Incident Herpes Zoster and Risk of Dementia: A Population-Based Danish Cohort Study

BACKGROUND AND OBJECTIVES

Herpes zoster (HZ) is caused by reactivation of the neurotrophic varicella-zoster virus (VZV). Zoster may contribute to development of dementia through neuroinflammation, cerebral vasculopathy, or direct neural damage, but epidemiologic evidence is limited. We used data from linked nationwide Danish registries to conduct a cohort study of the association between zoster and dementia during 1997-2017. As secondary aims, we examined whether associations were more pronounced for zoster involving cranial nerves (mainly ophthalmic zoster) or the CNS and Alzheimer disease as an outcome.

METHODS

We included people aged ≥40 years with zoster and a general population comparison cohort matched 5:1 by sex and birth year. We identified zoster and dementia in the registries using prescription records in the community and hospital diagnoses. We used Cox regression to compute confounder-adjusted hazard ratios (HRs) with 95% CIs for dementia associated with zoster during 0-1 year and 1-21 years of follow-up. We compared the cumulative incidence of dementia, inverse probability weighted for confounders.

RESULTS

The study included 247,305 people with zoster and 1,235,890 matched general population comparators (median age 64 years; 61% female). The HR of all-cause dementia was 0.98 (95% CI 0.92-1.04) during the first year and 0.93 (95% CI 0.90-0.95) thereafter in people with zoster vs matched comparators. Dementia was diagnosed in 9.7% of patients with zoster and 10.3% of matched comparators by the end of follow-up. We observed no increased long-term risk of dementia in subgroup analyses, except possibly in people with CNS infection (HR 1.94; 95% CI 0.78-4.80). Analyses of Alzheimer disease as a separate outcome showed similar results.

DISCUSSION

HZ is not associated with an increased risk of dementia, and contrary to expectation, we found a small decrease in the risk. The explanation for this finding is unclear, and systematic errors should be considered. Patients with CNS involvement had an almost 2-fold increased relative risk of dementia. The population attributable fraction of dementia due to this rare complication is estimated at 0.014%. Therefore, universal vaccination against VZV in the elderly is unlikely to reduce dementia risk.

Development and Validation of a Primary Care Electronic Health Record Phenotype to Study Migration and Health in the UK

International migrants comprised 14% of the UK's population in 2020; however, their health is rarely studied at a population level using primary care electronic health records due to difficulties in their identification. We developed a migration phenotype using country of birth, visa status, non-English main/first language and non-UK-origin codes and applied it to the Clinical Practice Research Datalink (CPRD) GOLD database of 16,071,111 primary care patients between 1997 and 2018. We compared the completeness and representativeness of the identified migrant population to Office for National Statistics (ONS) country-of-birth and 2011 census data by year, age, sex, geographic region of birth and ethnicity. Between 1997 to 2018, 403,768 migrants (2.51% of the CPRD GOLD population) were identified: 178,749 (1.11%) had foreign-country-of-birth or visa -status codes, 216,731 (1.35%) non-English-main/first-language codes, and 8288 (0.05%) non-UK-origin codes. The cohort was similarly distributed versus ONS data by sex and region of birth. Migration recording improved over time and younger migrants were better represented than those aged ≥50. The validated phenotype identified a large migrant cohort for use in migration health research in CPRD GOLD to inform healthcare policy and practice. The under-recording of migration status in earlier years and older ages necessitates cautious interpretation of future studies in these groups.

Perceived psychological stress and risk of herpes zoster: a nationwide population-based cohort study

BACKGROUND

Psychological stress may reduce cellular immunity, but its role in triggering latent infections, including herpes zoster (HZ), is controversial.

OBJECTIVES

To examine the association between perceived psychological stress and risk of HZ.

METHODS

In a linked registry-based cohort study, we followed 77 310 persons aged 40 years or older who participated in the 2010 Danish National Health Survey from 1 May 2010 until HZ diagnosis, death, emigration or 1 July 2014, whichever occurred first. We computed hazard ratios (HRs) of HZ associated with Cohen's Perceived Stress Scale (PSS) score (range 0-40) using Cox regression with age as the timescale, adjusted for sex, immunosuppressive and selected chronic conditions, immunosuppressive drugs, and sociodemographic, lifestyle and anthropometric factors. The PSS measures chronic stress perceived by an individual in response to various demands of daily life. We modelled the PSS score using quintiles and a restricted cubic spline function.

RESULTS

The unadjusted rate of HZ varied from 5·53 to 7·20 per 1000 person-years from the lowest to the highest PSS score quintile. Compared with the lowest PSS score quintile, the adjusted HR for HZ was 1·00 [95% confidence interval (CI) 0·86-1·16], 1·08 (95% CI 0·92-1·26), 1·05 (95% CI 0·90-1·23) and 1·14 (95% CI 0·97-1·34) for the second to the fifth quintile, respectively. In cubic spline analyses, PSS scores < 20 were not associated with increased HR of HZ, but thereafter the HR increased linearly from 1·10 (95% CI 0·85-1·41) to 2·22 (95% CI 1·32-3·75).

CONCLUSIONS

Our study indicated that high levels of psychological stress are associated with increased risk of HZ.

A systematic literature review of herpes zoster incidence worldwide

We conducted a systematic review to characterize the incidence rate of herpes zoster (HZ) in the general population, specifically in individuals ≥50 years of age. A total of 69 publications were included in the review. We found a cumulative incidence of HZ ranging from 2.9–19.5 cases per 1,000 population and an incidence rate of HZ ranging from 5.23–10.9 cases per 1,000 person-years. The cumulative incidence (3.22–11.2 versus 2.44–8.0 cases per 1,000 population) and incidence rates (6.05–12.8 versus 4.30–8.5 cases per 1,000 person-years) were higher in females than males. Studies revealed a trend of increasing incidence of HZ with increasing age and over time. Variations in incidence estimates can be attributed to the various study designs, case ascertainments, age distributions of the population and year of the study. HZ is associated with a substantial disease burden and is expected to increase due to population aging.

Associations of Lifestyle and Anthropometric Factors With the Risk of Herpes Zoster: A Nationwide Population-Based Cohort Study

The role of lifestyle in development of herpes zoster remains unclear. We examined whether smoking status, alcohol consumption, body mass index, or physical activity were associated with zoster risk. We followed a population-based cohort of 101,894 respondents to the 2010 Danish National Health Survey (baseline, May 1, 2010) until zoster diagnosis, death, emigration, or July 1, 2014, whichever occurred first. We computed hazard ratios for zoster associated with each exposure, using Cox regression with age as the time scale and adjusting for potential confounders. Compared with never smokers, hazards for zoster were increased in former smokers (1.17, 95% confidence interval (CI): 1.06, 1.30), but not in current smokers (1.00, 95% CI: 0.89, 1.13). Compared with low-risk alcohol consumption, neither intermediate-risk (0.95, 95% CI: 0.84, 1.07) nor high-risk alcohol consumption (0.99, 95% CI: 0.85, 1.15) was associated with zoster. We also found no increased hazard associated with weekly binge drinking versus not (0.93, 95% CI: 0.77, 1.11). Risk of zoster varied little by body mass index (referent = normal weight) and physical activity levels (referent = light level), with hazard ratios between 0.96 and 1.08. We observed no dose-response association between the exposures and zoster. The examined lifestyle and anthropometric factors thus were not risk factors for zoster.

Incidence of Hospitalizations and Emergency Department Visits for Herpes Zoster in Immunocompromised and Immunocompetent Adults in Ontario, Canada, 2002-2016

BACKGROUND

Immunocompromised adults are at .increased risk of herpes zoster (HZ) infection and related complications. We aimed to assess the incidence of hospital-attended HZ (ie, seen in hospital or emergency department) in immunocompromised populations and compare it to immunocompetent populations.

METHODS

We calculated incidence rates (IRs) of hospital-attended HZ in Ontario, Canada, between 1 April 2002 and 31 August 2016 in adults ≥18 years of age categorized as immunocompromised or immunocompetent. We repeated these analyses by type of immunocompromising condition and provided incidence rate ratios (IRRs) comparing to immunocompetent adults. We also calculated IRs and IRRs of HZ complications by immunocompromised status.

RESULTS

There were 135 206 incident cases of hospital-attended HZ during the study period. Immunocompromised adults accounted for 13% of these cases despite representing 3% of the population. The risk of hospital-attended HZ was higher for immunocompromised adults compared with immunocompetent adults (IRR, 2.9 [95% confidence interval {CI}, 2.9-3.0]) and ranged across type of immunocompromising conditions, from 2.6 (95% CI, 2.6-2.7) in those with a solid tumor malignancy to 12.3 (95% CI, 11.3-13.2) in those who had undergone hematopoietic stem cell transplant. The risk of any HZ complication was higher in immunocompromised adults (IRR, 3.6 [95% CI, 3.5-3.7]) and highest for disseminated zoster (IRR, 32.8 [95% CI, 27.8-38.6]).

CONCLUSIONS

The risk of hospital-attended HZ and related complications was higher in immunocompromised populations compared with immunocompetent populations. Our findings underscore the high-risk nature of this population and the potential benefits that may be realized through HZ vaccination.

Herpes zoster in older adults in Ontario, 2002-2016: Investigating incidence and exploring equity

Older adults are at increased risk of herpes zoster (HZ) and post-herpetic neuralgia (PHN) and HZ vaccines are available to help prevent infection. The objective of our study was to provide updated data on incidence of HZ and PHN related to clinical and demographic factors in older adults to inform immunization practices. We conducted a population-based, retrospective cohort study and included all cases of HZ seen in outpatient, emergency department, and hospital settings for adults aged 65 years and over between April 1, 2002 to August 31, 2016 in Ontario, Canada. We calculated the incidence of HZ and PHN, and estimated the proportion within each subgroup that developed PHN. We also assessed incidence by neighbourhood-level income quintile before and after the availability of vaccine for private purchase. The average annual incidence of HZ in any setting was 59.0 per 10,000 older adults, with higher incidence in outpatient as opposed to hospital settings. Incidence was higher in the oldest age groups, females, and those classified as immunocompromised or frail. Relative to the pre-vaccine era, the disparities in incidence of HZ by neighbourhood-level income increased, with higher rates of HZ and PHN seen in those residing in lower income quintiles. Additional prevention efforts should be targeted toward adults who are immunocompromised, frail, and those living in lower socioeconomic quintiles. Future work should assess the impact of the zoster vaccine program with a particular focus on equity in the publicly-funded era.

Safety of inadvertent administration of live zoster vaccine to immunosuppressed individuals in a UK-based observational cohort analysis

OBJECTIVES

To investigate the safety of live attenuated varicella zoster vaccination when administered to immunosuppressed individuals.

DESIGN

Prospective observational cohort study.

SETTING

The study used anonymised data from the Clinical Practice Research Datalink (CPRD), comprising a representative sample of routinely collected primary care data in England between 2013 and 2017 and and linked Hospital Episode Statistics data.

PARTICIPANTS

168 767 individuals age-eligible for varicella zoster vaccination registered at a general practice in England contributing data to CPRD.

MAIN OUTCOME MEASURES

Electronic health records indicating immunosuppression, zoster vaccination, diagnoses of specific varicella-zoster virus (VZV)-related disease and non-specific rash/encephalitis compatible with VZV-related disease.

RESULTS

Between 1 September 2013 and 31 August 2017, a period of immunosuppression was identified for 9093/168 767 (5.4%; 95% CI: 5.3%-5.5%) individuals age-eligible for zoster vaccination. The overall rate of vaccination while immunosuppressed was 1742/5251 (33.2 per 100 adjusted person years at risk; 95% CI: 31.9%-34.5%). Follow-up of the 1742 individuals who were inadvertently vaccinated while immunosuppressed identified only two cases of VZV-related disease within 8 weeks of vaccination (0.1%; 95% CI: 0.01%-0.4%), both primary care diagnoses of 'shingles', neither with a related hospital admission.

CONCLUSIONS

Despite evidence of inadvertent vaccination of immunosuppressed individuals with live zoster vaccination, there is a lack of evidence of severe consequences including hospitalisation. This should reassure primary care staff and encourage vaccination of mildly immunosuppressed individuals who do not meet current thresholds for contraindication. These findings support a review of the extent to which live zoster vaccination is contraindicated among the immunosuppressed.

Risk factors for modified vaccine effectiveness of the live attenuated zoster vaccine among the elderly in England

Background

The United Kingdom introduced routine vaccination with the live-attenuated zoster vaccine for 70 year-olds in 2013, with the vaccine also offered to 79 year-olds as part of a catch-up campaign. In the subsequent years, the catch-up campaign was extended to also include adults aged 78 years. We investigated 14 pre-identified potential risk factors for potential modified vaccine effectiveness.

Methods

This retrospective cohort study in England included subjects born in 1943-1946 (the routine cohort) and in 1934-1937 (the catch-up cohort). We used the Clinical Practice Research Datalink (CPRD) to identify herpes zoster (HZ) cases and the risk factors: age, gender, ethnicity, socio-economic status, asthma, type 2 diabetes, chronic obstructive pulmonary disease, smoking, body mass index, immunosuppression, history of HZ, co-administration with influenza or pneumococcal vaccine. We derived HZ incidence by risk groups, overall vaccine effectiveness (VE) and modified VE expressed as relative differences in VE from Poisson regression models.

Results

Overall VE was 66.8% [95% CI: 62.2; 71.0]. Two out of the 14 investigated risk factors modified the HZ VE. Notably, lower VE was observed in diabetics and in persons with a history of HZ with relative differences in VE of -22·2%, [95% CI: -39·6, -4·5] and -22·5%, [95% CI: -44·9, -0·1].

Conclusions

Live-attenuated zoster vaccine protection against HZ was lower in type 2 diabetics and in subjects with a history of HZ. Contrary to clinical trial results, age did not affect the observed VE. Further study is required to gain insights into why certain risk groups are less protected. Identifying and understanding the effect modifiers of VE is important for future vaccine development as well as vaccine recommendations.

Zoster vaccination inequalities: A population based cohort study using linked data from the UK Clinical Practice Research Datalink

OBJECTIVE

To quantify inequalities in zoster vaccine uptake by determining its association with socio-demographic factors: age, gender, ethnicity, immigration status, deprivation (at Lower-layer Super Output Area-level), care home residence and living arrangements.

METHOD

This population-based cohort study utilised anonymised primary care electronic health records from England (Clinical Practice Research Datalink) linked to deprivation and hospitalisation data. Data from 35,333 individuals from 277 general practices in England and eligible for zoster vaccination during the two-year period (2013-2015) after vaccine introduction were analysed. Logistic regression was used to obtain adjusted odds ratios (aOR) for the association of socio-demographic factors with zoster vaccine uptake for adults aged 70 years (main target group) and adults aged 79 years (catch-up group).

RESULTS

Amongst those eligible for vaccination, 52.4% (n = 18,499) received the vaccine. Socio-demographic factors independently associated with lower zoster vaccine uptake in multivariable analyses were: being older (catch-up group: aged 79 years) aOR = 0.89 (95% confidence interval (CI):0.85-0.93), care home residence (aOR = 0.64 (95%CI: 0.57-0.73)) and living alone (aOR = 0.85 (95%CI: 0.81-0.90)). Uptake decreased with increasing levels of deprivation (p-value for trend<0.0001; aOR most deprived versus least deprived areas = 0.69 (95%CI: 0.64-0.75)). Uptake was also lower amongst those of non-White ethnicities (for example, Black versus White ethnicity: aOR = 0.61 (95%CI: 0.49-0.75)) but was not lower among immigrants after adjusting for ethnicity. Lower uptake was also seen amongst females compared to men in the catch-up group.

CONCLUSIONS

Inequalities in zoster vaccine uptake exist in England; with lower uptake among those of non-White ethnicities, and among those living alone, in a care home and in more deprived areas. Tailored interventions to increase uptake in these social groups should assist in realising the aim of mitigating vaccination inequalities. As care home residents are also at higher risk of zoster, improving the uptake of zoster vaccination in this group will also mitigate inequalities in zoster burden.