Impact of Pneumococcal Conjugate Vaccines on Pneumonia Hospitalizations in High- and Low-Income Subpopulations in Brazil

Convergent impact of vaccination and antibiotic pressures on pneumococcal populations

Streptococcus pneumoniae is a remarkably adaptable and successful human pathogen, playing dual roles of both asymptomatic carriage in the nasopharynx and invasive disease including pneumonia, bacteremia, and meningitis. Efficacious vaccines and effective antibiotic therapies are critical to mitigating morbidity and mortality. However, clinical interventions can be rapidly circumvented by the pneumococcus by its inherent proclivity for genetic exchange. This leads to an underappreciated interplay between vaccine and antibiotic pressures on pneumococcal populations. Circulating populations have undergone dramatic shifts due to the introduction of capsule-based vaccines of increasing valency imparting strong selective pressures. These alterations in population structure have concurrent consequences on the frequency of antibiotic resistance profiles in the population. This review will discuss the interactions of these two selective forces. Understanding and forecasting the drivers of antibiotic resistance and capsule switching are of critical importance for public health, particularly for such a genetically promiscuous pathogen as S. pneumoniae.

Trends in Pneumococcal and Bacterial Meningitis in Brazil from 2007 to 2019

The pneumococcal conjugate vaccination (PCV) was introduced into the Brazilian Childhood National Immunization Program in 2010; however, universal pneumococcal vaccination for older adults has not been implemented yet. Our aim is to evaluate the trends in pneumococcal meningitis incidence and case fatality rate (CFR) across all age groups from 2007 to 2019 using data from the National Surveillance System. The pre-PCV (2007-2009) and post-PCV (2011-2019) periods were compared; changes in incidence and CFR were assessed by joinpoint regression. Additional analyses of bacterial meningitis were performed to compare the patterns and trends. Over the 13-year period, 81,203 and 13,837 cases were classified as bacterial and pneumococcal meningitis, respectively. S. pneumoniae was the main etiological agent of bacterial meningitis in adults aged ≥50 years and the most lethal in all age groups. In the post-PCV period, a 56.5% reduction in the average incidence was seen in pneumococcal meningitis in the pediatric population. In contrast, there was an increasing trend among adults. The CFR for pneumococcal and bacterial meningitis remained stable in most age groups during the study period. These findings highlight the value of expanding pneumococcal vaccination policies, including vaccines that provide better indirect protection from children to adults and broadening vaccination to older adults.

Impact of PCV10 on pediatric pneumococcal disease burden in Brazil: time for new recommendations?

OBJECTIVE

To describe the impact of the 10-valent pneumococcal conjugate vaccine on the pediatric burden of pneumococcal infections, carriage, serotype replacement, and antimicrobial resistance in Brazil since its introduction in 2010.

DATA SOURCE

A narrative review of English, Spanish, and Portuguese articles published in online databases and in Brazilian epidemiological surveillance databases was performed. The following keywords were used: Streptococcus pneumoniae, pneumococcal disease, conjugate vaccine, PCV10, antimicrobial resistance, and meningitis.

SUMMARY OF THE FINDINGS

Declines in hospitalization rates of all-cause pneumonia occurred in the target age groups and some age groups not targeted by vaccination early after the use of PCV10. Large descriptive studies of laboratory-confirmed pneumococcal meningitis and hospital-based historical series of hospitalized children with IPD have evidenced a significant impact on disease burden, in-hospital fatality rates, and admission to the intensive care unit before and after the inclusion of the vaccine. Impact data on otitis media is limited and inconsistent; the main benefit remains the prevention of complicated diseases. During the late post-vaccine years, a significant and progressive increase in high-level penicillin non-susceptibility pneumococci has been described. Since 2014 serotype 19A has been the leading serotype in all ages and was responsible for 28.2%-44.6% of all IPD in children under 5 yrs.

CONCLUSIONS

PCV10 has performed a significant impact on IPD in Brazil since 2010, however, progress has been continuously hampered by replacement. Broader spectrum PCVs could provide expanded direct and indirect protection against ST19A and other additional serotypes of increasing importance if administered to children in the Brazilian National Immunization Program.

Cost-utility and cost-benefit analysis of pediatric PCV programs in Egypt

New vaccine introductions (NVIs) raise issues of value for money (VfM) for self-financing middle-income countries like Egypt. We evaluate a pediatric pneumococcal conjugate vaccine (PCV) NVI in Egypt from health payer and societal perspectives, using cost-utility and cost-benefit analysis (CUA, CBA). We evaluate vaccinating 100 successive birth cohorts with the 13-valent PCV ("PCV13") and the 10-valent PCV ("PCV10") relative to no vaccination and each other. We quantify health effects with a disease incidence projection model and a multiple-cohort static disease model. Our CBA uses a health-augmented lifecycle model to generate willingness-to-pay for health gains from which we calculate rates of return (RoR). We obtain parameters from the published literature. We perform deterministic and probabilistic sensitivity analysis. Our base-case CUA finds incremental cost-effectiveness ratios (ICERs) for PCV13 and PCV10 relative to no program of $926 (95% confidence interval $512-$1,735) and $1,984 ($1,186-$3,805) per quality-adjusted life year (QALY), respectively; and for PCV13 relative to PCV10 of $174 ($88-$331) per QALY. Our base-case CBA finds RoRs to PCV13 and PCV10 relative to no program of 488% (188-993%) and 164% (33-336%), respectively, and to PCV13 relative to PCV10 of 3109% (1410-6602%). Both CUA and CBA find PCV13 to be good VfM relative to PCV10.

Evaluating the Impact of Meningococcal Vaccines With Synthetic Controls

Invasive meningococcal disease (IMD) has a low and unpredictable incidence, presenting challenges for real-world evaluations of meningococcal vaccines. Traditionally, meningococcal vaccine impact is evaluated by predicting counterfactuals from pre-immunization IMD incidences, possibly controlling for IMD in unvaccinated age groups, but the selection of controls can influence results. We retrospectively applied a synthetic control (SC) method, previously used for pneumococcal disease, to data from 2 programs for immunization of infants against serogroups B and C IMD in England and Brazil. Time series of infectious/noninfectious diseases in infants and IMD cases in older unvaccinated age groups were used as candidate controls, automatically combined in a SC through Bayesian variable selection. SC closely predicted IMD in absence of vaccination, adjusting for nontrivial changes in IMD incidence. Vaccine impact estimates were in line with previous assessments. IMD cases in unvaccinated age groups were the most frequent SC-selected controls. Similar results were obtained when excluding IMD from control sets and using other diseases only, particularly respiratory diseases and measles. Using non-IMD controls may be important where there are herd immunity effects. SC is a robust and flexible method that addresses uncertainty introduced when equally plausible controls exhibit different post-immunization behaviors, allowing objective comparisons of IMD programs between countries.

Impact of national introduction of ten-valent pneumococcal conjugate vaccine on invasive pneumococcal disease in Bangladesh: Case-control and time-trend studies

BACKGROUND

Bangladesh introduced the ten-valent pneumococcal conjugate vaccine (PCV10) into its national immunization program in March 2015 creating an opportunity to assess the real-world impact of PCV on invasive pneumococcal disease (IPD).

METHODS

Between January 2014 and June 2018, children aged 3-35 months in three rural sub-districts of Sylhet district of Bangladesh were visited every two months to collect morbidity and care-seeking data. Children attending sub-district hospitals with pneumonia, meningitis, or sepsis were assessed for IPD after obtaining informed consent. Blood and cerebrospinal fluid were collected from enrolled children to isolate pneumococcus using culture and molecular test. Children who were age-eligible to receive the PCV and had pneumococcus isolated were enrolled as cases. Four age and sex-matched clinic and community controls were selected for each case within one to two weeks of case identification. Data on immunization status and confounders were collected. PCV coverage was estimated using vaccine coverage surveys. Case-control and incidence trend analyses were conducted to assess the impact of PCV on IPD.

RESULTS

The community cohort yielded 217,605 child years of observations and 154,773 sick child-visits to study hospitals. Pneumococcus was isolated from 44 children who were age-eligible to receive PCV; these children were enrolled as cases. The cases were matched with 166 community- and 150 clinic-controls. The matched case-control analyses using community-controls showed 83% effectiveness (95% CI: 1.57-97.1%) and clinic controls showed 90% effectiveness (95% CI: -26.0% to 99.1%) of PCV in preventing IPD. Incidence trend analysis estimated vaccine effectiveness at 80.1% (95% CI: 38.4, 93.6).

CONCLUSION

PCV in this pediatric population in Bangladesh was highly effective in preventing IPD.

Levels of pneumococcal conjugate vaccine coverage and indirect protection against invasive pneumococcal disease and pneumonia hospitalisations in Australia: An observational study

BACKGROUND

There is limited empiric evidence on the coverage of pneumococcal conjugate vaccines (PCVs) required to generate substantial indirect protection. We investigate the association between population PCV coverage and indirect protection against invasive pneumococcal disease (IPD) and pneumonia hospitalisations among undervaccinated Australian children.

METHODS AND FINDINGS

Birth and vaccination records, IPD notifications, and hospitalisations were individually linked for children aged <5 years, born between 2001 and 2012 in 2 Australian states (New South Wales and Western Australia; 1.37 million children). Using Poisson regression models, we examined the association between PCV coverage, in small geographical units, and the incidence of (1) 7-valent PCV (PCV7)-type IPD; (2) all-cause pneumonia; and (3) pneumococcal and lobar pneumonia hospitalisation in undervaccinated children. Undervaccinated children received <2 doses of PCV at <12 months of age and no doses at ≥12 months of age. Potential confounding variables were selected for adjustment a priori with the assistance of a directed acyclic graph. There were strong inverse associations between PCV coverage and the incidence of PCV7-type IPD (adjusted incidence rate ratio [aIRR] 0.967, 95% confidence interval [CI] 0.958 to 0.975, p-value < 0.001), and pneumonia hospitalisations (all-cause pneumonia: aIRR 0.991 95% CI 0.990 to 0.994, p-value < 0.001) among undervaccinated children. Subgroup analyses for children <4 months old, urban, rural, and Indigenous populations showed similar trends, although effects were smaller for rural and Indigenous populations. Approximately 50% coverage of PCV7 among children <5 years of age was estimated to prevent up to 72.5% (95% CI 51.6 to 84.4) of PCV7-type IPD among undervaccinated children, while 90% coverage was estimated to prevent 95.2% (95% CI 89.4 to 97.8). The main limitations of this study include the potential for differential loss to follow-up, geographical misclassification of children (based on residential address at birth only), and unmeasured confounders.

CONCLUSIONS

In this study, we observed substantial indirect protection at lower levels of PCV coverage than previously described-challenging assumptions that high levels of PCV coverage (i.e., greater than 90%) are required. Understanding the association between PCV coverage and indirect protection is a priority since the control of vaccine-type pneumococcal disease is a prerequisite for reducing the number of PCV doses (from 3 to 2). Reduced dose schedules have the potential to substantially reduce program costs while maintaining vaccine impact.

Indirect effects of 13-valent pneumococcal conjugate vaccine on pneumococcal carriage in children hospitalised with acute respiratory infection despite heterogeneous vaccine coverage: an observational study in Lao People's Democratic Republic

Introduction

Empiric data on indirect (herd) effects of pneumococcal conjugate vaccines (PCVs) in settings with low or heterogeneous PCV coverage are limited. The indirect effects of PCV, which benefits both vaccinated and non-vaccinated individuals, are mediated by reductions in vaccine-type (VT) carriage (a prerequisite for disease). The aim of this study among hospitalised children in Lao People’s Democratic Republic (Lao PDR) is to determine the effectiveness of a 13-valent PCV (PCV13) against VT pneumococcal nasopharyngeal carriage (direct effects) and the association between village-level PCV13 coverage and VT carriage (indirect effects).

Methods

Pneumococcal nasopharyngeal carriage surveillance commenced in December 2013, shortly after PCV13 introduction (October 2013). We recruited and swabbed children aged 2–59 months admitted to hospital with acute respiratory infection. Pneumococci were detected using lytA quantitative real-time PCR and serotyped using microarray. PCV13 status and village-level PCV13 coverage were determined using written immunisation records. Associations between both PCV13 status and village-level PCV13 coverage and VT carriage were calculated using generalised estimating equations, controlling for potential confounders.

Results

We enrolled 1423 participants and determined PCV13 coverage for 368 villages (269 863 children aged under 5 years). By 2017, median village-level vaccine coverage reached 37.5%, however, the IQR indicated wide variation among villages (24.1–56.4). Both receipt of PCV13 and the level of PCV13 coverage were independently associated with a reduced odds of VT carriage: adjusted PCV13 effectiveness was 38.1% (95% CI 4.1% to 60.0%; p=0.032); and for each per cent increase in PCV13 coverage, the estimated odds of VT carriage decreased by 1.1% (95% CI 0.0% to 2.2%; p=0.056). After adjustment, VT carriage decreased from 20.0% to 12.8% as PCV13 coverage increased from zero to 60% among under 5.

Conclusions

Despite marked heterogeneity in PCV13 coverage, we found evidence of indirect effects in Lao PDR. Individual vaccination with PCV13 was effective against VT carriage.

Incorporating Information on Control Diseases Across Space and Time to Improve Estimation of the Population-level Impact of Vaccines

BACKGROUND

The synthetic control method evaluates the impact of vaccines while adjusting for a set of control time series representing diseases that are unaffected by the vaccine. However, noise in control time series, particularly in areas with small counts, can obscure the association with the outcome, preventing proper adjustments. To overcome this issue, we investigated the use of temporal and spatial aggregation methods to smooth the controls and allow for adjustment of underlying trends.

METHODS

We evaluated the impact of pneumococcal conjugate vaccine on all-cause pneumonia hospitalizations among adults ≥80 years of age in 25 states in Brazil from 2005 to 2015. Pneumonia hospitalizations in this group indicated a strong increasing secular trend over time that may influence estimation of the vaccine impact. First, we aggregated control time series separately by time or space before incorporation into the synthetic control model. Next, we developed distributed lags models (DLMs) to automatically determine what level of aggregation was most appropriate for each control.

RESULTS

The aggregation of control time series enabled the synthetic control model to identify stronger associations between outcome and controls. As a result, the aggregation models and DLMs succeeded in adjusting for long-term trends even in smaller states with sparse data, leading to more reliable estimates of vaccine impact.

CONCLUSIONS

When synthetic control struggles to identify important prevaccine associations due to noise in control time series, users can aggregate controls over time or space to generate more robust estimates of the vaccine impact. DLMs automate this process without requiring prespecification of the aggregation level.

The impact and cost-effectiveness of introducing the 10-valent pneumococcal conjugate vaccine into the paediatric immunisation programme in Iceland-A population-based time series analysis

INTRODUCTION

Streptococcus pneumoniae is a cause of infections that range in severity from acute otitis media (AOM) to pneumonia and invasive pneumococcal disease (IPD). The 10-valent pneumococcal conjugate vaccine (PHiD-CV10) was introduced into the Icelandic paediatric immunisation programme in 2011. The aim was to estimate the population impact and cost-effectiveness of PHiD-CV10 introduction.

METHODS

Data on primary care visits from 2005-2015 and hospitalisations from 2005-2017 were obtained from population-based registries. A Bayesian time series analysis with synthetic controls was employed to estimate the number of cases of AOM, pneumonia and IPD that would have occurred between 2013-2017, had PHiD-CV10 not been introduced. Prevented cases were calculated by subtracting the observed number of cases from this estimate. The cost of the programme was calculated accounting for cost-savings due to prevented cases.

RESULTS

The introduction of PHiD-CV10 prevented 13,767 (95% credible interval [CI] 2,511-29,410) visits for AOM from 2013-2015, and prevented 1,814 (95%CI -523-4,512) hospitalisations for pneumonia and 53 (95%CI -17-177) admissions for IPD from 2013-2017. Visits for AOM decreased both among young children and among children 4-19 years of age, with rate ratios between 0.72-0.89. Decreases were observed in both pneumonia hospitalisations (rate ratios between 0.67-0.92) and IPD (rate ratios between 0.27-0.94). The total cost of implementing PHiD-CV10 in Iceland was -7,463,176 United States Dollars (USD) (95%CI -16,159,551-582,135) with 2.1 USD (95%CI 0.2-4.7) saved for every 1 USD spent.

CONCLUSIONS

The introduction of PHiD-CV10 was associated with large decreases in visits and hospitalisations for infections commonly caused by pneumococcus and was cost-saving during the first five years of the immunisation programme.

The impact of 10-valent pneumococcal conjugate vaccine upon hospitalization rate of children with pneumonia in different Brazilian administrative regions

BACKGROUND

Streptococcus pneumoniae is the most frequent bacterial causative agent of pneumonia. Due to its significant contribution to the morbidity and mortality profile and the country's economy, the 10-valent pneumococcal vaccine (PCV10) was introduced in Brazil in 2010. Brazil is divided into five administrative regions which differ in social-economic indices among each other. Estimates of PCV10 impact on hospitalization rates due to pneumonia stratified by distinct Brazilian regions are limited. We assessed this issue.

METHODS

This is a population-based ecological investigation. Data about hospitalizations due to pneumonia, asthma or urinary tract infection (UTI) among patients aged under 20 years in the pre-exposure (2003-2009) and in the post-exposure (2011-2017) periods were retrieved from the National Health System - Hospital Information System (SIH-SUS) database. The total resident population by age group in each year was retrieved from the Brazilian Institute for Geography and Statistics database. Hospitalization rates were estimated for each Brazilian region and the rates obtained in the pre-exposure and in the post-exposure periods were compared by Prais-Winsten regression. The Human Development Index (HDI) evolved differently in the distinct regions during the study period.

RESULTS

Overall, hospitalization rates due to pneumonia declined by 34.5%. Similar trends were observed for hospitalization rates due to asthma and UTI. The same pattern was observed in each Brazilian region. However, the North region was the only one that presented an exponential incidence decline pattern, which could be explained by PCV10 implementation (declined by 10.8% in the quadratic regression, p < 0.01). Only in the North region, significant decline was observed among patients aged 0-4 years (-12.5%; p = 0.01), 5-9 years (-38.5%; p < 0.01) or 10-14 years (-10.7%; p = 0.03).

CONCLUSION

Significant variation in the downward trend of hospitalization rate was only found in the North region, which evolved from very low HDI in 2003; medium HDI in 2010 to high HDI in 2017.

Estimated impact of the pneumococcal conjugate vaccine on pneumonia mortality in South Africa, 1999 through 2016: An ecological modelling study

BACKGROUND

Data on the national-level impact of pneumococcal conjugate vaccine (PCV) introduction on mortality are lacking from Africa. PCV was introduced in South Africa in 2009. We estimated the impact of PCV introduction on all-cause pneumonia mortality in South Africa, while controlling for changes in mortality due to other interventions.

METHODS AND FINDINGS

We used national death registration data in South Africa from 1999 to 2016 to assess the impact of PCV introduction on all-cause pneumonia mortality in all ages, with the exclusion of infants aged <1 month. We created a composite (synthetic) control using Bayesian variable selection of nondiarrheal, nonpneumonia, and nonpneumococcal deaths to estimate the number of expected all-cause pneumonia deaths in the absence of PCV introduction post 2009. We compared all-cause pneumonia deaths from the death registry to the expected deaths in 2012 to 2016. We also estimated the number of prevented deaths during 2009 to 2016. Of the 9,324,638 deaths reported in South Africa from 1999 to 2016, 12·6% were pneumonia-related. Compared to number of deaths expected, we estimated a 33% (95% credible interval (CrI) 26% to 43%), 23% (95%CrI 17% to 29%), 25% (95%CrI 19% to 32%), and 23% (95%CrI 11% to 32%) reduction in pneumonia mortality in children aged 1 to 11 months, 1 to 4 years, 5 to 7 years, and 8 to 18 years in 2012 to 2016, respectively. In total, an estimated 18,422 (95%CrI 12,388 to 26,978) pneumonia-related deaths were prevented from 2009 to 2016 in children aged <19 years. No declines were estimated observed among adults following PCV introduction. This study was mainly limited by coding errors in original data that could have led to a lower impact estimate, and unmeasured factors could also have confounded estimates.

CONCLUSIONS

This study found that the introduction of PCV was associated with substantial reduction in all-cause pneumonia deaths in children aged 1 month to <19 years. The model predicted an effect of PCV in age groups who were eligible for vaccination (1 months to 4 years), and an indirect effect in those too old (8 to 18 years) to be vaccinated. These findings support sustaining pneumococcal vaccination to reduce pneumonia-related mortality in children.

Estimating the power to detect a change caused by a vaccine from time series data

When evaluating the effects of vaccination programs, it is common to estimate changes in rates of disease before and after vaccine introduction. There are a number of related approaches that attempt to adjust for trends unrelated to the vaccine and to detect changes that coincide with introduction. However, characteristics of the data can influence the ability to estimate such a change. These include, but are not limited to, the number of years of available data prior to vaccine introduction, the expected strength of the effect of the intervention, the strength of underlying secular trends, and the amount of unexplained variability in the data. Sources of unexplained variability include model misspecification, epidemics due to unidentified pathogens, and changes in ascertainment or coding practice among others. In this study, we present a simple simulation framework for estimating the power to detect a decline and the precision of these estimates. We use real-world data from a pre-vaccine period to generate simulated time series where the vaccine effect is specified a priori. We present an interactive web-based tool to implement this approach. We also demonstrate the use of this approach using observed data on pneumonia hospitalization from the states in Brazil from a period prior to introduction of pneumococcal vaccines to generate the simulated time series. We relate the power of the hypothesis tests to the number of cases per year and the amount of unexplained variability in the data and demonstrate how fewer years of data influence the results.

Estimating the power to detect a change caused by a vaccine from time series data

When evaluating the effects of vaccination programs, it is common to estimate changes in rates of disease before and after vaccine introduction. There are a number of related approaches that attempt to adjust for trends unrelated to the vaccine and to detect changes that coincide with introduction. However, characteristics of the data can influence the ability to estimate such a change. These include, but are not limited to, the number of years of available data prior to vaccine introduction, the expected strength of the effect of the intervention, the strength of underlying secular trends, and the amount of unexplained variability in the data. Sources of unexplained variability include model misspecification, epidemics due to unidentified pathogens, and changes in ascertainment or coding practice among others. In this study, we present a simple simulation framework for estimating the power to detect a decline and the precision of these estimates. We use real-world data from a pre-vaccine period to generate simulated time series where the vaccine effect is specified a priori. We present an interactive web-based tool to implement this approach. We also demonstrate the use of this approach using observed data on pneumonia hospitalization from the states in Brazil from a period prior to introduction of pneumococcal vaccines to generate the simulated time series. We relate the power of the hypothesis tests to the number of cases per year and the amount of unexplained variability in the data and demonstrate how fewer years of data influence the results.

Population-based incidence and serotype distribution of invasive pneumococcal disease prior to introduction of conjugate pneumococcal vaccine in Bangladesh

BACKGROUND

Bangladesh introduced the 10-valent pneumococcal conjugate vaccine (PCV-10) in 2015. We measured population-based incidence of invasive pneumococcal disease (IPD) prior to introduction of PCV-10 to provide a benchmark against which the impact of PCV-10 can be assessed.

METHODS

We conducted population, facility and laboratory-based surveillance in children 0-59 months of age in three rural sub-districts of Sylhet district of Bangladesh from January 2014 to June 2015. All children received two-monthly home visits with one week recall for morbidity and care seeking. Children attending the three Upazilla Health Complexes (UHC, sub-district hospitals) in the surveillance area were screened for suspected IPD. Blood samples were collected from suspected IPD cases for culture and additionally, cerebrospinal fluid (CSF) was collected from suspected meningitis cases for culture and molecular testing. Pneumococcal isolates were serotyped by Quellung. Serotyping of cases detected by molecular testing was done by sequential multiplex polymerase chain reaction.

RESULTS

Children under surveillance contributed to 126,657 child years of observations. Sixty-three thousand three hundred eighty-four illness episodes were assessed in the UHCs. Blood specimens were collected from 8,668 suspected IPD cases and CSF from 177 suspected meningitis cases. Streptococcus pneumoniae was isolated from 46 cases; 32 (70%) were vaccine serotype. The population-based incidence of IPD was 36.3/100,000 child years of observations. About 80% of the cases occurred in children below two years of age.

DISCUSSION

IPD was common in rural Bangladesh suggesting the potential benefit of an effective vaccine. Measurement of the burden of IPD requires multiple surveillance modalities.

Challenges in Estimating the Impact of Vaccination with Sparse Data

BACKGROUND

The synthetic control model is a powerful tool to quantify the population-level impact of vaccines because it can adjust for trends unrelated to vaccination using a composite of control diseases. Because vaccine impact studies are often conducted using smaller, subnational datasets, we evaluated the performance of synthetic control models with sparse time series data. To obtain more robust estimates of vaccine impacts from noisy time series, we proposed a possible alternative approach, STL+PCA method (seasonal-trend decomposition plus principal component analysis), which first extracts smoothed trends from the control time series and uses them to adjust the outcome.

METHODS

Using both the synthetic control and STL+PCA models, we estimated the impact of 10-valent pneumococcal conjugate vaccine on pneumonia hospitalizations among cases <12 months and 80+ years of age during 2004-2014 at the subnational level in Brazil. We compared the performance of these models using simulation analyses.

RESULTS

The synthetic control model was able to adjust for trends unrelated to 10-valent pneumococcal conjugate vaccine in larger states but not in smaller states. Simulation analyses showed that the estimates obtained with the synthetic control approach were biased when there were fewer cases, and only 4% of simulations had credible intervals covering the true estimate. In contrast, the STL+PCA analysis had 90% lower bias and had 95% of simulations, with credible intervals covering the true estimate.

CONCLUSIONS

Estimates from the synthetic control model might be biased when data are sparse. The STL+PCA model provides more accurate evaluations of vaccine impact in smaller populations.

Postintroduction Study of Cost-Effectiveness of Pneumococcal Vaccine PCV10 from Public Sector Payer's Perspective in the State of Santa Catarina, Brazil

OBJECTIVES

To evaluate cost-effectiveness of 10-valent pneumococcal conjugate vaccine in the routine immunization program for children younger than 5 years in Brazil by a postintroduction study.

METHODS

Ecological study of prevaccine (2006-2009) versus postvaccine (2011-2014) period related the changes in mortality rate and hospitalization rate to direct cost of pneumonia treatment from the payer's perspective to estimate the cost-effectiveness regarding lives saved, life-years gained, and disability-adjusted life-year for children younger than 5 years in the southern Brazilian state of Santa Catarina. All-cause pneumonia (ICD-10 J12-J18) deaths, hospital admissions, and associated costs were retrieved from the Brazilian Ministry of Health official Web site. Life expectancy at birth, population, ambulatory costs, cost savings, and plausible range of these parameters were used from published sources. Computer simulations with sensitivity analysis were performed to obtain the cost-effectiveness estimates.

RESULTS

About 27 lives were saved and 2573 hospitalizations averted by the 10-valent pneumococcal conjugate vaccine vaccination in the 2011 to 2014 period at the cost of US $24,348 per life-year gained and US $27,748 per disability-adjusted life-year. The latter cost is 81% of Brazilian gross domestic product per capita over the same period.

CONCLUSIONS

The vaccine was very cost-effective according to the World Health Organization criterion.