Douglas C. Dover

Twenty-five–year follow-up among survivors of childhood acute lymphoblastic leukemia: a report from the Childhood Cancer Survivor Study

Survivors of childhood acute lymphoblastic leukemia (ALL) are at risk for late effects of cancer therapy. Five-year ALL survivors (< 21 years at diagnosis; n = 5760 eligible, 4151 participants), diagnosed from 1970 to 1986 were compared with the general population and a sibling cohort (n = 3899). Cumulative mortality of 5760 5-year survivors was 13% at 25 years from diagnosis. Recurrent ALL (n = 483) and second neoplasms (SNs; n = 89) were the major causes of death. Among 185 survivors, 199 SNs occurred, 53% in the CNS. Survivors reported more multiple chronic medical conditions (CMCs; odds ratio [OR], 2.8; 95% CI, 2.4-3.2) and severe or life-threatening CMCs (OR, 3.6; 95% CI, 3.0-4.5) than siblings. Cumulative incidence of severe CMCs, including death, 25 years from diagnosis was 21.3% (95% CI, 18.2-24.4; 23.3% [95% CI, 19.4-27.2] and 13.4% [95% CI, 8.4-18.4] for irradiated and nonirradiated survivors, respectively). Survivors reported more adverse general and mental health, functional impairment, and activity limitations compared with siblings (P < .001). Rates of marriage, college graduation, employment, and health insurance were all lower compared with sibling controls (P < .001). Long-term survivors of childhood ALL exhibit excess mortality and morbidity. Survivors who received radiation therapy as part of their treatment or had a leukemia relapse are at greatest risk for adverse outcomes.

Twenty years of follow-up among survivors of childhood and young adult acute myeloid leukemia: A report from the Childhood Cancer Survivor Study

Limited data exist on the comprehensive assessment of late medical and social effects experienced by survivors of childhood and young adult acute myeloid leukemia (AML).

Shingles in Alberta: before and after publicly funded varicella vaccination.

PURPOSE A universal publicly funded chickenpox vaccination program was implemented in Alberta in 2002. We examine the epidemiology of medically attended shingles in Alberta from 1994 to 2010. METHODS Incident shingles cases (earliest health service utilizations for ICD-9 053 or ICD-10-CA B02) and their co-morbid conditions for the 12 months prior to shingles diagnosis were identified from the records of Albertas universal, publicly funded health-care insurance system for 1994-2010. Shingles diagnostic codes at least 180 days after the first were classified as recurrent episodes. Denominators for rates were estimated using mid-year population estimates from the Alberta Health Care Insurance Plan Registry. Annual age- and sex-specific rates were estimated. We estimated the proportion of all cases that were hospitalized. We explored the pattern of rates for sex, age-group co-morbidity and year effects and their interactions. RESULTS Crude rates of shingles increased over the interval 1994-2010. Most persons had only a single episode of shingles; 4% of cases were hospitalized. Shingles rates were higher among females than males. While only 2% of shingles cases had one or more co-morbidities, this proportion was also higher for females than males. Prior to 2002, all age groups of both sexes experienced increasing annual rates of shingles. However, there was a sharp decline in the rate of shingles for both females and males under the age of 10 years for 2002-2010, the period in which there was publicly funded chickenpox vaccination. CONCLUSION The declining rates of shingles among persons under the age of 10 years are consistent with an impact of the chickenpox vaccination program. The trend of increasing rates of shingles among older persons began prior to implementation of vaccination.

Risk of febrile seizures after first dose of measles–mumps–rubella–varicella vaccine: a population-based cohort study

Background: The combination measles–mumps–rubella–varicella (MMRV) vaccine currently used in Canada (Priorix-Tetra) may increase the risk of febrile seizures relative to the separate vaccines (MMR and varicella) previously administered. We determined the risk of febrile seizure after the first dose of MMRV, as well as any additional risk for children at high risk for seizures because of pre-existing medical conditions. Methods: In this retrospective, population-based cohort study, we compared the risk of seizures after the first dose of MMRV with the risk after same-day administration of separate MMR and varicella vaccines (MMR+V) in children 12 to 23 months of age in the province of Alberta. We deterministically linked vaccination data to health service utilization data for seizures. We used Poisson regression, with adjustment for age and calendar year, to determine the risk for the full cohort and for high-risk children. Results: The risk of seizures 7 to 10 days after vaccination was twice as high with MMRV as with MMR+V (relative risk [RR] 1.99, 95% confidence interval [CI] 1.30–3.05). The excess absolute risk of seizures was 3.52 seizures per 10 000 doses of MMRV relative to MMR+V. In high-risk children, the risk was not differentially higher for MMRV (RR 1.30, 95% CI 0.60–2.79). Interpretation: Despite an increased risk of febrile seizures following MMRV (compared with MMR+V), the absolute level of risk was small. Policy-makers need to balance these findings with the potential benefits of administering the combination vaccine or determine whether the choice of vaccine rests with clinicians and/or parents.

Determining rubella immunity in pregnant Alberta women 2009-2012.

Rubella IgG levels for 157,763 pregnant women residing in Alberta between 2009 and 2012 were analyzed. As there have been no reported cases of indigenous rubella infection in Canada since 2005, there has been a lack of naturally acquired immunity, and the current prenatal population depends almost entirely on vaccine induced immunity for protection. Rubella antibody levels are significantly lower in younger maternal cohorts with 16.8% of those born prior to universal vaccination programs (1971-1980), and 33.8% of those born after (1981-1990) having IgG levels that are not considered protective (<15 IU/mL). Analysis across pregnancies showed only 35.0% of women responded with a 4-fold increase in antibody levels following post-natal vaccination. Additionally, 41.2% of women with antibody levels <15 IU/mL had previously received 2 doses of rubella containing vaccine. These discordant interpretations generate a great deal of confusion for laboratorians and physicians alike, and result in significant patient follow-up by Public Health teams. To assess the current antibody levels in the prenatal population, latent class modeling was employed to generate a two class fit model representing women with an antibody response to rubella, and women without an antibody response. The declining level of vaccine-induced antibodies in our population is disconcerting, and a combined approach from the laboratory and Public Health may be required to provide appropriate follow up for women who are truly susceptible to rubella infection.

How to determine protective immunity in the post-vaccine era

abstract The ability to determine an individuals susceptibility to infection relies heavily on the assay used, and the ability to correlate results of the assay to a clinical interpretation. Current rubella immunity screening methods identify total rubella IgG antibodies circulating in the serum, however both humoral and cell mediated immune responses have been shown to contribute to protection from infection. Therefore, antibody screening assays may under-estimate immunity in some populations. In fact, waning antibody titers over time in a large prenatal population were recently documented in North America, and the trend has been echoed in other countries that have achieved elimination through universal rubella vaccination. Despite decreasing antibody titers, the number of acute rubella cases has not increased in these populations, suggesting that the lower antibody levels may still be protective. Based on the changing epidemiology in universally vaccinated populations, it may be time to reassess the level of antibody that indicates immunity to rubella infection.

The effectiveness of shingles vaccine among Albertans aged 50 years or older: A retrospective cohort study

PURPOSE We assessed the effectiveness of shingles vaccine in preventing incident shingles among Alberta residents aged 50 years or older over the period 2009 - 2015, using administrative health data. METHODS The cohort comprised of Albertans from the Alberta Health Care Insurance Plan Registry (AHCIP) as of June 30, 2009 and aged 50 years or older. Those who received shingles vaccine were identified from the provincial pharmaceutical information network. The occurrence of incident shingles was identified through both inpatient and outpatients/community care data. Incident shingles was defined as the earliest dated record of ICD 9-CM 053 or ICD-10-CA B02. Starting on November 1, 2009, individuals with no history of shingles or shingles vaccination were followed until Nov 1, 2015 (6 years), or until shingles incidence, death, or AHCIP cancellation (including leaving Alberta). Vaccine effectiveness (VE) was estimated as the inverse of the relative risk of developing incident shingles in each year following vaccination compared to time at risk without vaccination, while adjusting for age, sex, income quintile, and immune compromising conditions (identified from physician claims, inpatient, and cancer registry data). RESULTS There were 1,094,236 individuals in the cohort, with 85,439 (7.80%) vaccinated individuals. The shingles incidence rate was 9.03 [95% CI: 8.95, 9.11] cases per 1,000 person years (49,243 cases). Adjusted VE in the first year following immunization was 50.02% [95% CI: 44.71%, 54.83%] against incident shingles, decreasing to no effect by the fifth year (VE = 14.00% [95% CI: -20.99%, 38.88%]). CONCLUSIONS Our findings are consistent with observations from other population based studies and provide population level data for policy-makers to review when making decisions related to public funding of shingles vaccine.

Economic impact of switching rubella IgG methodologies to the prenatal public health program in Alberta

BACKGROUND Despite widespread use of a universal rubella standard, variability in rubella antibody titre can be observed between assays, particularly at the low end of the linear range. OBJECTIVES Here, we investigate the impact of a methodology change for rubella IgG from the Abbott AXSYM to the Abbott Architect in a comprehensive prenatal screening program in the Canadian province of Alberta. STUDY DESIGN 51,815 specimens (21,399 tested by AxSYM and 30,416 tested by Architect) submitted for routine prenatal screening between January 2006 and December 2012 from women who lived in Alberta after the universal childhood immunization programme for rubella was implemented, and whose immunization records were available, were included in the study. RESULTS Prenatal samples tested by AxSYM for rubella IgG were approximately 30% higher than those reported by Architect. Among individuals who had tests across multiple pregnancies, the change in test platform led to an additional 7% of women who initially tested positive, becoming non-positive (i.e. negative or indeterminate) in their subsequent tests. The tendency of the Architect IgG assay to report lower quantitative values was demonstrated across all birth cohorts and vaccination status, and resulted in an additional 2800 women requiring vaccination between 2010 and 2012 with an estimated cost of

Is varicella vaccination associated with pediatric arterial ischemic stroke? A population-based cohort study

38,500. CONCLUSION The change in rubella IgG screening assay resulted in a significant increase in the number of women who required post partum vaccination and Public Health follow-up.

Twenty Year Follow up of Survivors of Childhood Acute Lymphoid Leukemia: A Report from the Childhood Cancer Survivor Study (CCSS).

BACKGROUND AND PURPOSE Varicella disease is a risk factor for pediatric Arterial Ischemic Stroke (AIS). Isolated case reports have emerged suggesting that varicella vaccination may also pose a risk for AIS. METHODS This retrospective population-based cohort study assessed the risk of AIS in children who received a varicella-containing vaccine, as compared to those who did not. The study cohort consisted of children born between January 1, 2006 and December 31, 2013, in the Canadian province of Alberta, where all routine childhood vaccinations are publicly-funded, and recorded in a central immunization repository. These data were linked with hospital discharge abstract data to identify children diagnosed with AIS. A Cox proportional hazard model assessed the risk of AIS in the 12 months following vaccination for children receiving a varicella vaccine between 11 and 23 months of age, as compared to non-vaccinated children. RESULTS Of the 368,992 children in the cohort, 325,729 were vaccinated with a varicella-containing vaccine between 11 and 23 months of age. The rate of AIS was 7.8 (95% CI 4.8-10.9) per 100,000 person years at risk in the 12 months following varicella vaccination, as compared to 6.8 (95% CI 1.3-12.2) for children who did not receive a varicella vaccine. The adjusted Hazard Ratio for the risk of AIS, controlling for other AIS risk factors, in vaccinated children as compared to non-vaccinated children was 1.6 (95% CI 0.7-3.7) in the 12 months following vaccination and 1.7 (95% CI 0.5-4.9) in the 30 days following vaccination. CONCLUSIONS Our study found no evidence of an increased risk of AIS following varicella vaccination. This population-based cohort study provides reassurance to parents and clinicians regarding the safety of varicella vaccination.