Simulation-based sample size calculations of marginal proportional means models for recurrent events with competing risks.

In randomised controlled trials, the outcome of interest could be recurrent events, such as hospitalisations for heart failure. If mortality rates are non-negligible, both recurrent events and competing terminal events need to be addressed when formulating the estimand and statistical analysis is no longer trivial. In order to design future trials with primary recurrent event endpoints with competing risks, it is necessary to be able to perform power calculations to determine sample sizes. This paper introduces a simulation-based approach for power estimation based on a proportional means model for recurrent events and a proportional hazards model for terminal events. The simulation procedure is presented along with a discussion of what the user needs to specify to use the approach. The method is flexible and based on marginal quantities which are easy to specify. However, the method introduces a lack of a certain type of dependence. This is explored in a sensitivity analysis which suggests that the power is robust in spite of that. Data from a randomised controlled trial, LEADER, is used as the basis for generating data for a future trial. Finally, potential power gains of recurrent event methods as opposed to first event methods are discussed.

Case study of semaglutide and cardiovascular outcomes: An application of the Causal Roadmap to a hybrid design for augmenting an RCT control arm with real-world data.

Introduction: Increasing interest in real-world evidence has fueled the development of study designs incorporating real-world data (RWD). Using the Causal Roadmap, we specify three designs to evaluate the difference in risk of major adverse cardiovascular events (MACE) with oral semaglutide versus standard-of-care: (1) the actual sequence of non-inferiority and superiority randomized controlled trials (RCTs), (2) a single RCT, and (3) a hybrid randomized-external data study. Methods: The hybrid design considers integration of the PIONEER 6 RCT with RWD controls using the experiment-selector cross-validated targeted maximum likelihood estimator. We evaluate 95% confidence interval coverage, power, and average patient time during which participants would be precluded from receiving a glucagon-like peptide-1 receptor agonist (GLP1-RA) for each design using simulations. Finally, we estimate the effect of oral semaglutide on MACE for the hybrid PIONEER 6-RWD analysis. Results: In simulations, Designs 1 and 2 performed similarly. The tradeoff between decreased coverage and patient time without the possibility of a GLP1-RA for Designs 1 and 3 depended on the simulated bias. In real data analysis using Design 3, external controls were integrated in 84% of cross-validation folds, resulting in an estimated risk difference of -1.53%-points (95% CI -2.75%-points to -0.30%-points). Conclusions: The Causal Roadmap helps investigators to minimize potential bias in studies using RWD and to quantify tradeoffs between study designs. The simulation results help to interpret the level of evidence provided by the real data analysis in support of the superiority of oral semaglutide versus standard-of-care for cardiovascular risk reduction.

A causal roadmap for generating high-quality real-world evidence.

Increasing emphasis on the use of real-world evidence (RWE) to support clinical policy and regulatory decision-making has led to a proliferation of guidance, advice, and frameworks from regulatory agencies, academia, professional societies, and industry. A broad spectrum of studies use real-world data (RWD) to produce RWE, ranging from randomized trials with outcomes assessed using RWD to fully observational studies. Yet, many proposals for generating RWE lack sufficient detail, and many analyses of RWD suffer from implausible assumptions, other methodological flaws, or inappropriate interpretations. The Causal Roadmap is an explicit, itemized, iterative process that guides investigators to prespecify study design and analysis plans; it addresses a wide range of guidance within a single framework. By supporting the transparent evaluation of causal assumptions and facilitating objective comparisons of design and analysis choices based on prespecified criteria, the Roadmap can help investigators to evaluate the quality of evidence that a given study is likely to produce, specify a study to generate high-quality RWE, and communicate effectively with regulatory agencies and other stakeholders. This paper aims to disseminate and extend the Causal Roadmap framework for use by clinical and translational researchers; three companion papers demonstrate applications of the Causal Roadmap for specific use cases.

Bivariate pseudo-observations for recurrent event analysis with terminal events.

The analysis of recurrent events in the presence of terminal events requires special attention. Several approaches have been suggested for such analyses either using intensity models or marginal models. When analysing treatment effects on recurrent events in controlled trials, special attention should be paid to competing deaths and their impact on interpretation. This paper proposes a method that formulates a marginal model for recurrent events and terminal events simultaneously. Estimation is based on pseudo-observations for both the expected number of events and survival probabilities. Various relevant hypothesis tests in the framework are explored. Theoretical derivations and simulation studies are conducted to investigate the behaviour of the method. The method is applied to two real data examples. The bivariate marginal pseudo-observation model carries the strength of a two-dimensional modelling procedure and performs well in comparison with available models. Finally, an extension to a three-dimensional model, which decomposes the terminal event per death cause, is proposed and exemplified.

Methodological challenges in the analysis of recurrent events for randomised controlled trials with application to cardiovascular events in LEADER.

Analysis of recurrent events is becoming increasingly popular for understanding treatment effects in randomised controlled trials. The analysis of recurrent events can improve efficiency and capture disease burden compared to standard time-to-first event analyses. However, the added knowledge about the multi-state process comes at the cost of modelling complexity. High mortality rates can complicate matters even more. A case study using data from a randomised controlled trial, LEADER, is presented to highlight interpretation of common methods as well as potential pitfalls when analysing recurrent events in the presence of a competing risk. The presented methods either target features of the underlying intensity functions or marginal traits of a multi-state process which includes terminal events or not. In particular, approaches to handle death as a part of an event and as a competing risk are discussed. A new method targeting the marginal mean function for a composite endpoint, which includes both death as a component and as a competing risk, will be introduced. Finally, recommendations for how to capture meaningful treatment effects in randomised controlled trials when analysing recurrent and terminal events will be made.

Semaglutide Effects on Cardiovascular Outcomes in People With Overweight or Obesity (SELECT) rationale and design.

Cardiovascular disease (CVD) is a major cause of morbidity and mortality. Although it has been widely appreciated that obesity is a major risk factor for CVD, treatments that produce effective, durable weight loss and the impact of weight reduction in reducing cardiovascular risk have been elusive. Instead, progress in CVD risk reduction has been achieved through medications indicated for controlling lipids, hyperglycemia, blood pressure, heart failure, inflammation, and/or thrombosis. Obesity has been implicated as promoting all these issues, suggesting that sustained, effective weight loss may have independent cardiovascular benefit. GLP-1 receptor agonists (RAs) reduce weight, improve glycemia, decrease cardiovascular events in those with diabetes, and may have additional cardioprotective effects. The GLP-1 RA semaglutide is in phase 3 studies as a medication for obesity treatment at a dose of 2.4 mg subcutaneously (s.c.) once weekly. Semaglutide Effects on Heart Disease and Stroke in Patients with Overweight or Obesity (SELECT) is a randomized, double-blind, parallel-group trial testing if semaglutide 2.4 mg subcutaneously once weekly is superior to placebo when added to standard of care for preventing major adverse cardiovascular events in patients with established CVD and overweight or obesity but without diabetes. SELECT is the first cardiovascular outcomes trial to evaluate superiority in major adverse cardiovascular events reduction for an antiobesity medication in such a population. As such, SELECT has the potential for advancing new approaches to CVD risk reduction while targeting obesity.

Complete and on-time routine childhood immunisation: determinants and association with severe morbidity in urban informal settlements, Nairobi, Kenya.

Background: Completion of the full series of childhood vaccines on-time is crucial to ensuring greater protection against vaccine-preventable diseases.Aim: To examine determinants of complete and on-time vaccination and evaluate the relationship between vaccination patterns and severe morbidity outcomes.Subjects and methods: Vaccination information from infants in Nairobi Urban Health and Demographic Surveillance System was used to evaluate full and on-time vaccination coverage of routine immunisation. Logistic regression was used to identify determinants of full and on-time vaccination coverage. Cox regression model was used to evaluate the relationship between vaccination status and subsequent severe morbidity. A shared frailty cox model was fitted to account for the heterogeneity in hospitalisation episodes.Results: Maternal age, post-natal care, parity, ethnicity, and residence place were identified as determinants of vaccination completion. Institutional deliveries and residence place were identified as the determinants of on-time vaccination. A significant 58% (confidence interval [CI]: 15-79%) (p = .017) lower mortality was observed among fully immunised children compared with not fully immunised. Lower mortality was observed among on-time immunised children, 64% (CI: 20-84%) compared to those with delays.Conclusions: Improving vaccination timeliness and completion schedule is critical for protection against vaccine preventable diseases and may potentially provide protection beyond these targets.

Modeling marginal features in studies of recurrent events in the presence of a terminal event.

We study models for recurrent events with special emphasis on the situation where a terminal event acts as a competing risk for the recurrent events process and where there may be gaps between periods during which subjects are at risk for the recurrent event. We focus on marginal analysis of the expected number of events and show that an Aalen-Johansen type estimator proposed by Cook and Lawless is applicable in this situation. A motivating example deals with psychiatric hospital admissions where we supplement with analyses of the marginal distribution of time to the competing event and the marginal distribution of the time spent in hospital. Pseudo-observations are used for the latter purpose.

BCG Vaccination at Birth and Rate of Hospitalization for Infection Until 15 Months of Age in Danish Children: A Randomized Clinical Multicenter Trial.

BACKGROUND: The bacillus Calmette-Guérin (BCG) vaccine against tuberculosis might reduce the non-tuberculosis-related child mortality rate in low-income settings. We tested the hypothesis that BCG vaccination at birth would reduce early childhood hospitalization for infection in Denmark, a high-income setting. Hospitalization for infection was a secondary outcome in a randomized trial with the primary aim to estimate the potential non-specific effects of BCG vaccination at birth on all-cause hospitalization. METHODS: A total of 4262 children included in the Danish Calmette Study were assigned randomly to either receive the BCG vaccine or not and were followed through the Danish National Patient Register. The outcome was number of hospitalizations for infection until the age of 15 months. Data were analyzed by Cox regression in intention-to-treat (ITT) and per-protocol (PP) analyses. RESULTS: In the ITT analysis, we observed 588 hospitalizations for infection (mean, 0.28 hospitalization per child) among the 2129 children allocated to receive the BCG vaccine and 595 hospitalizations for infection (mean, 0.28 hospitalization per child) among the 2133 children allocated to the control group (hazard ratio [HR], 0.99 [95% confidence interval (CI), 0.85-1.15]). The PP analysis yielded an HR of 1.00 (95% CI, 0.86-1.16).Predefined interaction ITT analyses showed that among 740 children with a BCG-vaccinated mother, the HR for BCG-vaccinated children was 0.65 (95% CI, 0.45-0.94); the HR for children who had a non-BCG-vaccinated mother was 1.10 (95% CI, 0.93-1.29) (P = .01, test of no interaction). Cesarean delivery modified the effect of BCG vaccination (HRs, 0.73 [95% CI, 0.54-0.99] in children born by cesarean section vs 1.10 [95% CI, 0.92-1.30] in other children; P = .02). When the outcome was defined as time to first hospitalization, the HR for premature children after BCG vaccination was 1.81 (95% CI, 0.95-3.43), whereas the HR was 0.94 (95% CI, 0.82-1.08) for children born at term (P = .05). CONCLUSION: BCG vaccination did not affect the rate of hospitalization for infection up to the age of 15 months in Danish children. In future studies, the role of maternal BCG-vaccination, premature birth, and cesarean delivery needs further exploration.

Where girls are less likely to be fully vaccinated than boys: Evidence from a rural area in Bangladesh.

BACKGROUND: Immunization is one of the most successful and effective health intervention to reduce vaccine preventable diseases for children. Recently, Bangladesh has made huge progress in immunization coverage. In this study, we compared the recent immunization coverage between boys and girls in a rural area of Bangladesh. SETTING: The study is based on data from Chakaria Health and Demographic Surveillance System (HDSS) of icddr,b, which covers a population of 90,000 individuals living in 16,000 households in 49 villages. METHODS: We calculated the coverage of fully immunized children (FIC) for 4584 children aged 12-23 months of age between January 9, 2012 and January 19, 2016. We analyzed immunization coverage using crude FIC coverage ratio (FCR) and adjusted FCR (aFCR) from binary regression models. The dynamic of gender inequality was examined across sociodemographic and economic conditions. MAIN OUTCOME MEASURE: The adjusted female/male (F/M) FIC coverage ratios in various sociodemographic and economic categories. RESULTS: Among children who lived below the lower poverty line, the F/M aFCR was 0.89 (0.84-0.94) compared to 0.98 (0.95-1.00) for children from the households above lower poverty line (p = 0.003, test for interaction). For children of mothers with no high school education, the F/M aFCR was 0.94 (0.91-0.97), whereas it was 1.00 (0.96-1.04) for children of mothers who attended high school (p = 0.04, test for interaction). The F/M aFCR was 1.01 (0.96-1.06) for first born children but 0.95 (0.93-0.98) for second or higher birth order children (p = 0.04, test for interaction). CONCLUSIONS: Fewer girls than boys were completely vaccinated by their first birthday due to girls' lower coverage for measles vaccine. The tendency was most marked for children living below the poverty line, for children whose mothers did not attend high school, and for children of birth order two or higher. In the study setting and similar areas, sex differentials in coverage should be taken into account in ongoing immunization programmes.

National Immunization Campaigns with Oral Polio Vaccine Reduce All-Cause Mortality: A Natural Experiment within Seven Randomized Trials.

BACKGROUND: A recent WHO review concluded that live BCG and measles vaccine (MV) may have beneficial non-specific effects (NSEs) reducing mortality from non-targeted diseases. NSEs of oral polio vaccine (OPV) were not examined. If OPV vaccination campaigns reduce the mortality rate, it would suggest beneficial NSEs. SETTING: Between 2002 and 2014, Guinea-Bissau had 15 general OPV campaigns and other campaigns with OPV plus vitamin A supplementation (VAS), VAS-only, MV, and H1N1 vaccine. In this period, we conducted seven randomized controlled trials (RCTs) with mortality as main outcome. METHODS: Within these RCTs, we assessed whether the mortality rate was lower after-campaign than before-campaign. We used Cox models with age as underlying time and further adjusted for low birth-weight, season and time trend in mortality. We calculated the adjusted mortality rate ratio (MRR) for after-campaign vs before-campaign. RESULTS: The mortality rate was lower after OPV-only campaigns than before, the MRR being 0.81 (95% CI = 0.68-0.95). With each additional dose of campaign-OPV the mortality rate declined further (MRR = 0.87 (95% CI: 0.79-0.96) per dose) (test for trend, p = 0.005). No other type of campaign had similar beneficial effects. Depending on initial age and with follow-up to 3 years of age, the number needed to treat with campaign-OPV-only to save one life was between 68 and 230 children. CONCLUSION: Bissau had no case of polio infection so the results suggest that campaign-OPV has beneficial NSEs. Discontinuation of OPV-campaigns in low-income countries may affect general child mortality levels negatively.

Rapid Protective Effects of Early BCG on Neonatal Mortality Among Low Birth Weight Boys: Observations From Randomized Trials.

Background: Three randomized trials (RCTs) in low-weight (<2.5 kg) infants have shown that Bacille Calmette-Guérin (BCG) vaccine nonspecifically reduces all-cause mortality in the neonatal period. Methods: Using data from 3 RCTs of early BCG (n = 6583) we examined potential sex differences in the timing of the mortality reduction in the neonatal period, presenting metaestimates of the main outcome mortality rate ratios (MRR) for BCG-vaccinated and controls. Results: Among controls, boys had a particularly high mortality during the first week after randomization: male-female MRR 2.71 (95% CI, 1.70-4.50). During the first week, BCG had a marked beneficial effect for boys, reducing mortality 3-fold (MRR [BCG/no BCG] = 0.36 [0.20-0.67]). In weeks 2-4 the effect waned for boys (MRR = 0.91 [0.51-1.69]). In girls, the pattern was opposite with a limited effect in the first week (MRR = 0.85 [0.46-1.54]), but a significant reduction in weeks 2-4 (MRR = 0.56 [0.31-1.00]). This was consistent in all 3 trials. Verbal autopsies linked early benefit to fewer sepsis-related deaths among BCG-vaccinated boys. Discussion: The marked reduction in mortality in the days after BCG vaccination in boys emphasizes the importance of providing BCG soon after birth. Trial registration numbers: ClinicalTrials.gov (NCT00146302) and ClinicalTrials.gov (NCT00625482).

The Effect of Smallpox and Bacillus Calmette-Guérin Vaccination on the Risk of Human Immunodeficiency Virus-1 Infection in Guinea-Bissau and Denmark.

BACKGROUND: The live smallpox and Bacillus Calmette-Guérin (BCG) vaccinations have been associated with better adult survival in both Guinea-Bissau and Denmark. In Guinea-Bissau, human immunodeficiency virus (HIV)-1 became an important cause of death after smallpox vaccination was phased out globally in 1980. We hypothesised that smallpox and BCG vaccinations were associated with a lower prevalence of HIV-1 infection, and we tested this hypothesis in both Guinea-Bissau and Denmark. METHODS: We conducted 2 studies: (1) a cross-sectional study of HIV infection and vaccination scars in Guinea-Bissau including 1751 individuals and (2) a case-base study with a background population of 46239 individuals in Denmark. In Guinea-Bissau, HIV-1 transmission was almost exclusively sexually transmitted. In Denmark, we excluded intravenous drug users. Data were analyzed using logistic regression. RESULTS: Bacillus Calmette-Guérin and/or smallpox vaccination compared with neither of these vaccines was associated with an adjusted odds ratio (aOR) for HIV-1 of 0.62 (95% confidence interval [CI], 0.36-1.07) in Guinea-Bissau and 0.70 (95% CI, 0.43-1.15) in Denmark. We combined the results from both settings in a meta-analysis (aOR = 0.66; 95% CI, 0.46-0.96). Data from Guinea-Bissau indicated a stronger effect of multiple smallpox vaccination scars (aOR = 0.27; 95% CI, 0.10-0.75) as follows: women, aOR = 0.18 (95% CI, 0.05-0.64); men, aOR = 0.52 (95% CI, 0.12-2.33); sex-differential effect, P = .29. CONCLUSIONS: The studies from Guinea-Bissau and Denmark, 2 very different settings, both suggest that the BCG and smallpox vaccines could be associated with a decreased risk of sexually transmitted HIV-1. It might be informative to pursue this observation and explore possible protective mechanisms as part of the search for an HIV-1 vaccine.

Co-administration of BCG and Diphtheria-tetanus-pertussis (DTP) Vaccinations May Reduce Infant Mortality More Than the WHO-schedule of BCG First and Then DTP. A Re-analysis of Demographic Surveillance Data From Rural Bangladesh.

BACKGROUND: WHO recommends BCG at birth and diphtheria-tetanus-pertussis (DTP)-containing vaccine at 6, 10 and 14weeks of age. However, BCG and DTP are often co-administered in low-income countries. The health implications have not been examined. SETTING: We reanalysed data from Matlab, Bangladesh, to examine the influence of co-administration on mortality; 37,894 children born 1986-1999 were followed with registration of vaccinations and survival. METHODS: Using Cox models, survival was analysed from 6weeks to 9months of age when measles vaccine is given; 712 children died in this age group. We calculated mortality rate ratios (MRR) for children starting the vaccination schedule with BCG-first, BCG+DTP1-first or DTP1-first. RESULTS: Only 17% followed the WHO-schedule with BCG-first. Mortality was 16/1000 person-years for children who initiated the vaccination schedule with BCG+DTP1 but 32/1000 and 20/1000 for children who received BCG-first or DTP-first, respectively. Compared with BCG+DTP1-first and adjusting for background factors, the BCG-first-schedule was associated with 2-fold higher mortality (MRR=1.94 (1.42-2.63)). DTP1 administered after BCG-first was associated with higher mortality than receiving DTP1 with BCG (MRR=1.78 (1.03-3.03)). CONCLUSIONS: Co-administration of BCG and DTP may further reduce mortality. Since all observational studies support this trend, co-administration of BCG and DTP should be tested in randomised trials.

Fewer out-of-sequence vaccinations and reduction of child mortality in Northern Ghana.

BACKGROUND: Studies suggest that diphtheria-tetanus-pertussis (DTP) vaccine administered simultaneously with measles vaccine (MV) or DTP administered after MV are associated with higher child mortality than having MV-after-DTP3 as most recent vaccination. We tested this in Northern Ghana where the prevalence of such out-of-sequence vaccinations has declined. METHODS: Using annual cohort data of children aged 12-23months from 1996 to 2012 and Cox proportional hazards models, we assessed survival in relation to the most recent vaccination status within the next 12months and until five years of age. We assessed whether mortality in children aged 12-59months was higher when the most recent vaccine was non-live (DTP) rather than live (MV or OPV). RESULTS: Out-of-sequence vaccinations with DTP-containing vaccines and MV declined from 86% in 1989 to 24% in 1996 and 0.7% in 2012. Between 1996 and 2012, 38 070 children had their vaccinations status assessed: the adjusted hazard ratio (HR) for out-of-sequence vaccinations (DTP>=MV) compared with the recommended sequence of MV-after-DTP3 was 1.42(1.06-1.90) during the first 12months after assessment of vaccination status and 1.29(1.03-1.60) with follow-up to five years of age; the HR was 2.58(1.14-5.84) before OPV or MV campaigns and 1.37(1.02-1.85) after the campaigns. CONCLUSION: Out-of-sequence vaccinations with DTP and MV are associated with higher mortality than MV as most recent vaccination; the effect is unlikely to be due to confounding. Hence, the reduction in out-of-sequence vaccinations may have lowered child mortality. It is recommended not to give DTP with MV or DTP after MV.

Palivizumab Exposure and the Risk of Atopic Dermatitis, Asthma and Allergic Rhinoconjunctivitis: A Cross-National, Population-Based Cohort Study.

BACKGROUND: Palivizumab is a humanized monoclonal antibody designed to provide passive immunity against respiratory syncytial virus. It is prescribed to children at high risk for severe infection with respiratory syncytial virus. However, little is known about the risk of the immune-mediated diseases atopic dermatitis, asthma, and allergic rhinoconjunctivitis after palivizumab exposure. AIM: Our objective was to investigate whether exposure to palivizumab was associated with atopic dermatitis, asthma, or allergic rhinoconjunctivitis in childhood. METHODS: This was a cross-national population-based cohort study including data from 769,523 Danish children born 1 January 1999-31 December 2010 and 581,742 Swedish children born 1 July 2005-31 December 2010. Since palivizumab is only indicated for children at the highest risk, sub-cohorts of preterm children, children with bronchopulmonary dysplasia, and children with hemodynamic significant heart disease were defined. RESULTS: Of the 1,351,265 children included, 1192 (0.09%) were exposed to palivizumab. An increased risk of asthma after palivizumab exposure was observed in the total birth cohort (hazard ratio [HR] 1.49; 95% confidence interval [CI] 1.32-1.68) and in the sub-cohort of preterm children (HR 1.24; 95% CI 1.07-1.44). However, post hoc analyses using the propensity score to balance confounding factors found no increased risk of asthma in preterm children (HR 0.91; 95% CI 0.56-1.48). No increased risks of atopic dermatitis (HR 1.18; 95% CI 0.94-1.48) or allergic rhinoconjunctivitis (HR 1.14; 95% CI 0.92-1.42) were observed. CONCLUSION: Exposure to palivizumab neither increased the risk of atopic disease nor protected against asthma.

BCG vaccination at birth and early childhood hospitalisation: a randomised clinical multicentre trial.

BACKGROUND: The BCG vaccine is administered to protect against tuberculosis, but studies suggest there may also be non-specific beneficial effects upon the infant immune system, reducing early non-targeted infections and atopic diseases. The present randomised trial tested the hypothesis that BCG vaccination at birth would reduce early childhood hospitalisation in Denmark, a high-income setting. METHODS: Pregnant women planning to give birth at three Danish hospitals were invited to participate. After parental consent, newborn children were allocated to BCG or no intervention within 7 days of age. Randomisation was stratified by prematurity. The primary study outcome was number of all-cause hospitalisations analysed as repeated events. Hospitalisations were identified using The Danish National Patient Register. Data were analysed by Cox proportional hazards models in intention-to-treat and per-protocol analyses. RESULTS: 4184 pregnant women were randomised and their 4262 children allocated to BCG or no intervention. There was no difference in risk of hospitalisation up to 15 months of age; 2129 children randomised to BCG experienced 1047 hospitalisations with a mean of 0.49 hospitalisation per child compared with 1003 hospitalisations among 2133 control children (mean 0.47), resulting in a HR comparing BCG versus no BCG of 1.05 (95% CI 0.93 to 1.18) (intention-to-treat analysis). The effect of BCG was the same in children born at term (1.05 (0.92 to 1.18)) and prematurely (1.07 (0.63 to 1.81), p=0.94). The effect was also similar in the two sexes and across study sites. The results were essentially identical in the per-protocol analysis and after adjustment for baseline characteristics. CONCLUSIONS: BCG vaccination at birth did not reduce the risk of hospitalisation for somatic acquired disease until 15 months of age in this Danish study population. TRIAL REGISTRATION NUMBER: NCT01694108, results.

Vaccinations against smallpox and tuberculosis are associated with better long-term survival: a Danish case-cohort study 1971-2010.

Background: When vaccinations with vaccinia against smallpox and Bacillus Calmette-Guérin (BCG) against tuberculosis were phased out in some high-income countries around 1980, the impact on overall mortality was not examined. Recent studies from low-income countries have suggested that these vaccines are associated with mortality reductions, not explained by specific disease protection. We examined whether vaccinia and BCG administered in childhood were associated with long-term mortality reductions in a high-income population. Methods: In this case-cohort study, we followed 47 622 schoolchildren from Copenhagen, Denmark, born 1965 to 1976, from their first health examination to 2010. This cohort experienced the phase-out of vaccinia and BCG vaccination programmes. Results: A sub-cohort of 5 316 individuals (699 excluded) was followed for 164 450 person-years (0.2% were lost to follow-up), and 401 deaths due to natural causes (841 deaths in total) occurred in the full cohort. Compared with individuals who had not received vaccinia or BCG, those who had received both vaccinia and BCG had an adjusted hazard ratio (aHR) of 0.54 [95% confidence interval (CI): 0.36-0.81] for mortality due to natural causes of death; those who only received BCG had an aHR of 0.58 (95% CI: 0.39-0.85). Vaccinia and BCG were not associated with any protection against deaths by accidents, suicide or murder, the combined aHR being 0.94 (95% CI: 0.62-1.42). Conclusions: Vaccinia and BCG vaccinations were associated with better long-term survival, which was not explained by specific protection. Vaccines with beneficial non-specific effects may reduce overall mortality even after the target diseases are eradicated.

Introduction of standard measles vaccination in an urban African community in 1979 and overall child survival: a reanalysis of data from a cohort study.

OBJECTIVE: To examine the effect of the first introduction of measles vaccine (MV) in Guinea-Bissau in 1979. SETTING: Urban community study of the anthropometric status of all children under 6 years of age. PARTICIPANTS: The study cohort included 1451 children in December 1978; 82% took part in the anthropometric survey. The cohort was followed for 2 years. INTERVENTION: In December 1979, the children were re-examined anthropometrically. The participating children, aged 6 months to 6 years, were offered MV if they did not have a history of measles infection. There were no routine vaccinations in 1979-1980. PRIMARY AND SECONDARY OUTCOME MEASURES: Age-adjusted mortality rate ratios (MRRs) for measles vaccinated and not vaccinated children; changes in nutritional status. RESULTS: The nutritional status deteriorated significantly from 1978 to 1979. Nonetheless, children who received MV at the December 1979 examination had significantly lower mortality in the following year (1980) compared with the children who had been present in the December 1978 examination but were not measles vaccinated. Among children still living in the community in December 1979, measles-vaccinated children aged 6-71 months had a mortality rate of 18/1000 person-years during the following year compared with 51/1000 person-years for absent children who were not measles vaccinated (MRR=0.30 (0.12-0.73)). The effect of MV was not explained by prevention of measles infection as the unvaccinated children did not die of measles infection. CONCLUSIONS: MV may have beneficial non-specific effects on child survival not related to the prevention of measles infection.