Appropriateness of administrative data for vaccine impact evaluation: the case of pneumonia hospitalizations and pneumococcal vaccine in Brazil

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.

Impact of meningococcal C conjugate vaccine on incidence of invasive meningococcal disease in an 18-year time-series in Brazil and in distinct Brazilian regions

OBJECTIVE

To evaluate the impact of meningococcal C conjugate (MCC) vaccine in Brazil.

METHODS

Ecological study assessing all invasive meningococcal disease (IMD) and meningococcal C disease (MenC) cases reported in all age groups, from 2001 to 2019. MCC was implemented in 2010. Data were collected on the DATASUS platform. Joinpoint regression was performed to assess the Annual Percent Change (APC) of the incidence rate.

RESULTS

IMD incidence decreased in all Brazilian regions from 2001 onwards, without apparent additional reduction attributable to MCC vaccine in the North, Northeast and South. The higher and statistically significant APC reduction in all age groups, in the North and South, and in children <5 years, in the Northeast, occurred between 2001-2011 (-15.4%), 2004-2012 (-14.4%), and 2001-2013 (-10.3%), respectively, before MCC vaccine implementation. Annual incidence of MenC in under 5 years significantly fell in the North (-6.8%; 2011-2018), Southeast (-40.6%; 2010-2015) and Midwest (-48.6%; 2010-2014), which may be attributable to MCC implementation.

CONCLUSION

IMD and MenC behaved differently after MCC vaccine implementation in Brazil during this 18-year time-series analysis. This suggests that the control of IMD should be based on multiple public health care measures and considered on a regional basis.

Evaluation strategies for measuring pneumococcal conjugate vaccine impact in low-resource settings

OBJECTIVES

Pneumococcal conjugate vaccines (PCVs) are effective in reducing pneumococcal disease. We measured 13-valent PCV (PCV13) effect on different pneumococcal outcomes using diverse studies in Lao People's Democratic Republic.

METHODS

Studies included: pre-PCV13 population-based record review of hospitalized childhood pneumonia cases; acute respiratory infection (ARI) study post-PCV13 to demonstrate effectiveness (VE) against hypoxic pneumonia; invasive pneumococcal disease (IPD) surveillance in all ages (2004-2018); carriage studies in children hospitalized with ARI (2013-2019); community carriage surveys pre- and post-PCV13.

RESULTS

Annual pneumonia incidence rate in children pre-PCV13 was 1,530 (95% confidence interval [CI] 1,477-1,584) per 100,000. Adjusted VE against hypoxic pneumonia was 37% (95% CI 6-57%). For IPD, 85% (11/13) of cases were due to vaccine-types pre-PCV13, and 43% (3/7) post-PCV13 in children aged <5 years; for ≥5 years, 61% (27/44) and 42% (17/40), respectively. For ARI cases, adjusted VE for vaccine-type carriage was 39% (95% CI 4-60) in <5 year olds; slightly higher than community surveys (23% [95% CI 4-39%] in 12-23 month olds).

CONCLUSIONS

Despite limited baseline data, we found evidence of PCV13 impact on disease and carriage. Our approach could be used in similar settings to augment existing WHO PCV evaluation guidelines.

Impact after 10-year use of pneumococcal conjugate vaccine in the Brazilian national immunization program: an updated systematic literature review from 2015 to 2020

In 2010, a 10-valent pneumococcal non-typeable Haemophilus influenzae protein D conjugate vaccine (PHiD-CV) was introduced in the Brazilian national immunization program; the 3 + 1 dose schedule was replaced by a 2 + 1 dose schedule in 2016. This systematic review presents the latest published evidence (2015–2020) on the impact after 10-year use of PHiD-CV in Brazil from a total of 29 publications. Overall, the PHiD-CV program had a positive impact on the morbidity and mortality associated with invasive pneumococcal disease (IPD), pneumonia and acute otitis media (AOM) in children <5 years-old. A reduction in the vaccine-type invasive disease was observed in all-ages; suggesting indirect protection unvaccinated older children and adults. The occurrence of non-vaccine type disease was evidenced in some studies. Higher vaccination coverage is required at national and state level for sustained population impact. Given the change in the vaccination schedule and the dynamics of pneumococcal disease epidemiology, continuous surveillance is warranted.

GSK Study identifier: HO-18-19438

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.

Impact of Brazil's More Doctors Program on hospitalizations for primary care sensitive cardiovascular conditions

Globally, cardiovascular diseases are the leading cause of disease burden and death. Timely and appropriate provision of primary care may lead to sizeable reductions in hospitalizations for a range of chronic and acute health conditions. In this paper, we study the impact of Brazil's More Doctors Program (MDP) on hospitalizations due to cerebrovascular disease and hypertension. We exploit the geographic variation in the uptake of the MPD and combine coarsened exact matching and difference-in-difference methods to construct valid counterfactual estimates. We use data from the Hospital Information System in Unified Health System, the MDP administrative records, the Brazilian Regulatory Agency, the Ministry of Health, and the Brazilian Institute of Geography and Statistics, covering the years from 2009 to 2017. Our analysis resulted in estimated coefficients of -1.47 (95%CI: -4.04,1.10) for hospitalizations for cerebrovascular disease and -1.20 (95%CI: -5.50,3.11) for hypertension, suggesting an inverse relationship between the MDP and hospitalizations. For cerebrovascular disease, the estimated MDP coefficient was -0.50 (95%CI: -2.94,1.95) in the year of program introduction, -5.21 (95%CI: -9.43,-0.99) and -8.21 (95%CI: -13.68,-2.75) in its third and fourth year of implementation, respectively. Our results further suggest that the beneficial impact of MDP on hospitalizations due to cerebrovascular disease became discernable in urban municipalities starting from the fourth year of implementation. We found no evidence that the MDP led to reductions in hospitalizations due to hypertension. Our results highlight that increased investment in resources devoted to primary care led to improvements in hospitalizations for selected cardiovascular conditions. However, it took time for the beneficial effects of the MDP to become discernable and the Program did not guarantee declines in hospitalizations for all cardiovascular conditions, suggesting that further improvements may be needed to enhance the beneficial impact of the MDP on the level and distribution of population health in Brazil.

Hospitalization Rate and Population-based Incidence of Hospitalization for Community-acquired Pneumonia Among Children in Suzhou, China

BACKGROUND

Data on hospitalization burden of community-acquired pneumonia (CAP) in children are very limited in China. This study aimed to estimate the hospitalization rate (HR) and population-based incidence of hospitalization of CAP for children <15 years of age in Suzhou, China.

METHODS

This was a retrospective study of children hospitalized in Soochow University Affiliated Children's Hospital from January 2010 to December 2014. Children who were residents of downtown Suzhou, 29 days to <15 years of age, with discharge diagnosis codes (International Classification of Diseases, 10th revision) including J09-J18 and J20-J22 were included. All-cause clinical community-acquired pneumonia (CCAP) and radiographically confirmed pneumonia (RCAP) were identified based on individual medical chart review. The HR and population-based cumulative incidence of hospitalization (HI) were calculated.

RESULTS

Among 184,734 children <15 years of age admitted to Soochow University Affiliated Children's Hospital during the study period, 31,302 children were identified as having CCAP and 24,218 (77.4%) children confirmed as having RCAP. CCAP hospitalization occurred year round and peaked during winter and early spring. The overall HRs for CCAP and RCAP were 189.0 [95% confidence interval (CI): 187.1-190.9] and 146.2 (95% CI: 144-148) per 1000 hospitalizations, respectively, and the HIs per 100,000 children annually were CCAP, 3235.8 (95% CI: 3207.3-3264.2) and RCAP, 2503.5 (95% CI: 2478.3-2528.6). For children <5 years of age, the HR for CCAP was 248.4 (95% CI: 245.9-250.9) and RCAP was 194.0 (95% CI: 191.4-196.3) per 1000 hospitalizations; the HI for CCAP was 6956.2 (95% CI: 6892.8-7019.6) and 5431.9 (95% CI: 5375.4-5488.4) per 100,000 children for RCAP. The highest HR and HI were observed in children 29 days to <6 months of age: HR for CCAP was 407.4 (95% CI: 400.9-413.9) per 1000 hospitalizations and HI for CCAP was 11,203.7 (95% CI: 11,026.8-11,380.6) per 100,000 children annually.

CONCLUSIONS

There is a considerable burden of CAP among children <15 years of age in Suzhou, particularly among children 29 days to <6 months of age and during winter and early spring. These data provide valuable information to monitor CAP trends over time in children of Suzhou, China.

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

Background

Pneumococcal conjugate vaccines (PCVs) are being used worldwide. A key question is whether the impact of PCVs on pneumonia is similar in low- and high-income populations. However, most low-income countries, where the burden of disease is greatest, lack reliable data that can be used to evaluate the impact. Data from middle-income countries that have both low- and high-income subpopulations can provide a proxy measure for the impact of the vaccine in low-income countries.

Methods

We evaluated the impact of PCV10 on hospitalizations for all-cause pneumonia in Brazil, a middle-income country with localities that span a broad range of human development index (HDI) levels. We used complementary time series and spatiotemporal methods (synthetic controls and hierarchical Bayesian spatial regression) to test whether the decline in pneumonia hospitalizations associated with vaccine introduction varied across the socioeconomic spectrum.

Results

We found that the declines in all-cause pneumonia hospitalizations in children and young and middle-aged adults did not vary substantially across low and high HDI subpopulations. Moreover, the estimated declines seen in infants and young adults were associated with higher levels of uptake of the vaccine at a local level.

Conclusions

These results suggest that PCVs have an important impact on hospitalizations for all-cause pneumonia in both low- and high-income 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.

Challenges to estimating vaccine impact using hospitalization data

Because the real-world impact of new vaccines cannot be known before they are implemented in national programs, post-implementation studies at the population level are critical. Studies based on analysis of hospitalization rates of vaccine-preventable outcomes are typically used for this purpose. However, estimates of vaccine impact based on hospitalization data are particularly prone to confounding, as hospitalization rates are tightly linked to changes in the quality, access and use of the healthcare system, which often occur simultaneously with introduction of new vaccines. Here we illustrate how changes in healthcare delivery coincident with vaccine introduction can influence estimates of vaccine impact, using as an example reductions in infant pneumonia hospitalizations after introduction of the 10-valent pneumococcal conjugate vaccine (PCV10) in Brazil. To this end, we explore the effect of changes in several metrics of quality and access to public healthcare on trends in hospitalization rates before (2008–09) and after (2011–12) PCV10 introduction in 2010. Changes in infant pneumonia hospitalization rates following vaccine introduction were significantly associated with concomitant changes in hospital capacity and the fraction of the population using public hospitals. Importantly, reduction of pneumonia hospitalization rates after PCV10 were also associated with the expansion of outpatient services in several Brazilian states, falling more sharply where primary care coverage and the number of health units offering basic and emergency care increased more. We show that adjustments for unrelated (non-vaccine) trends commonly employed by impact studies, such as use of single control outcomes, are not always sufficient for accurate impact assessment. We discuss several ways to identify and overcome such biases, including sensitivity analyses using different denominators to calculate hospitalizations rates and methods that track changes in the outpatient setting. Employing these practices can improve the accuracy of vaccine impact estimates, particularly in evolving healthcare settings typical of low- and middle-income countries.

Sustained Decrease in Gastroenteritis-related Deaths and Hospitalizations in Children Less Than 5 Years of Age After the Introduction of Rotavirus Vaccination: A Time-Trend Analysis in Brazil (2001-2010)

BACKGROUND

Rotavirus (RV) vaccine, Rotarix, was introduced into the Brazil national immunization program in 2006. To estimate population-level vaccine effect, we conducted a time-trend analysis on all-cause gastroenteritis (GE)-related death certificate-reported deaths (DCRDs), hospital deaths (HDs) and hospitalizations trends in <5-year-olds before and after RV vaccine introduction.

METHODS

National level all-cause GE-related death certificate [Mortality Information System] and admission (Hospital Information System) data were aggregated and analyzed. Negative-binomial regression models (adjusting for age, year and region) compared DCRDs, HDs and hospitalization trends in <5-year-olds between baseline (2001-2005) and postvaccine introduction periods (Mortality Information System: 2007-2009 and Hospital Information System: 2007-2010). Negative-binomial regression models were fitted to data for each outcome before 2006, and the predicted annual frequencies of each outcome were plotted against corresponding observed annual frequencies.

RESULTS

During the postvaccine introduction period, there was an overall age-independent GE-related DCRDs reduction (20.9%, P = 0.04) observed in children <5 years of age; a reduction was also seen in infants <1 year of age (20.8%, P = 0.003). Age-independent GE-related HDs and hospitalizations reductions (57.1%, P < 0.0001 and 26.6%, P < 0.0001, respectively) were observed in <5-year-olds; HDs reductions were also observed for each age group (<1-year-olds: 55.0%, P < 0.0001 and 1- to <5-year-olds: 59.5%, P < 0.0001). Observed annual frequencies of GE-related DCRDs, HDs and hospitalizations were lower than the predicted value in each age group in all years after 2006.

CONCLUSIONS

GE-related DCRDs, HDs and hospitalizations were significantly reduced in <1 and in 1- to <5-year-old Brazilian children after Rotarix introduction, which provides additional evidence of the direct and indirect population-level effect of RV vaccination on GE-related mortality and morbidity in children.

Sensitivity of the Dengue Surveillance System in Brazil for Detecting Hospitalized Cases

We evaluated the sensitivity of the dengue surveillance system in detecting hospitalized cases in ten capital cities in Brazil from 2008 to 2013 using a probabilistic record linkage of two independent information systems hospitalization (SIH-SUS) adopted as the gold standard and surveillance (SINAN). Sensitivity was defined as the proportion of cases reported to the surveillance system amid the suspected hospitalized cases registered in SIH-SUS. Of the 48,174 hospitalizations registered in SIH-SUS, 24,469 (50.7%) were reported and registered in SINAN, indicating an overall sensitivity of 50.8% (95%CI 50.3–51.2). The observed sensitivity for each of the municipalities included in the study ranged from 22.0% to 99.1%. The combination of the two data sources identified 71,161 hospitalizations, an increase of 97.0% over SINAN itself. Our results allowed establishing the proportion of underreported dengue hospitalizations in the public health system in Brazil, highlighting the use of probabilistic record linkage as a valuable tool for evaluating surveillance systems.

This manuscript address essential issues regarding the current and future challenges of a dengue surveillance system. Dengue fever is one of the major public health threats in a large area of the world, including Brazil which represents around 70% of the cases in the Americas. The dengue surveillance system in Brazil was established in 1986, but evaluations of this surveillance system were rarely conducted. The need for accurate data is of paramount importance due to not only the increase of severe cases in the past decade, but also to monitor the impact of a vaccine as soon as it occurs. The evaluation of the sensitivity of surveillance system is a challenge, due to the lack of a gold standard. In our study, we took advantage of two very well structured and independent information systems with nationwide coverage. The hospitalization information system was defined as the gold standard for hospitalized cases in the public health system and compared to the notifiable diseases information system using a probabilistic record linkage. Therefore, we were able to evaluate the sensitivity of the dengue surveillance system in detecting hospitalized cases in ten capital cities from 2008 to 2013 in Brazil.

Impact of the pneumococcal 10-valent vaccine on reducing hospitalization for community-acquired pneumonia in children

OBJECTIVE

To describe and analyze the occurrence of hospitalizations for community-acquired pneumonia in children before and after the pneumococcal 10-valent conjugate vaccine implementation into the National Immunization Program.

METHODS

This is an ecological study that includes records of children younger than one year old, vaccinated and not vaccinated with the pneumococcal 10-valent conjugate vaccine in the periods pre- and post-inclusion of the vaccine in the National Immunization Program in the area covered by the Regional Health Superintendence of Alfenas, state of Minas Gerais, Brazil. Vaccination was considered as the exposure factor and hospitalization for community-acquired pneumonia as the endpoint, using secondary annual data by municipality. The prevalence ratio and its 95% confidence interval (95%CI) were used to verify the association between variables. The Z test was used to calculate the difference between proportions.

RESULTS

Considering the 26 municipalities of the Regional Health Superintendence of Alfenas, there was a significant reduction in hospitalizations for community-acquired pneumonia in children younger than one year of age, with prevalence ratio (PR)=0.81 (95%CI: 0.74 to 0.89; p<0.05), indicating a 19% lower prevalence of hospitalization for community-acquired pneumonia in the post-vaccination period.

CONCLUSIONS

The results suggest the effectiveness of the pneumococcal 10-valent conjugate vaccine in preventing severe cases of community-acquired pneumonia in children younger than one year of age.

Impact of the pneumococcal 10-valent vaccine on reducing hospitalization for community-acquired pneumonia in children

OBJECTIVE

To describe and analyze the occurrence of hospitalizations for community-acquired pneumonia in children before and after the pneumococcal 10-valent conjugate vaccine implementation into the National Immunization Program.

METHODS

This is an ecological study that includes records of children younger than one year old, vaccinated and not vaccinated with the pneumococcal 10-valent conjugate vaccine in the periods pre- and post-inclusion of the vaccine in the National Immunization Program in the area covered by the Regional Health Superintendence of Alfenas, state of Minas Gerais, Brazil. Vaccination was considered as the exposure factor and hospitalization for community-acquired pneumonia as the endpoint, using secondary annual data by municipality. The prevalence ratio and its 95% confidence interval (95%CI) were used to verify the association between variables. The Z test was used to calculate the difference between proportions.

RESULTS

Considering the 26 municipalities of the Regional Health Superintendence of Alfenas, there was a significant reduction in hospitalizations for community-acquired pneumonia in children younger than one year of age, with prevalence ratio (PR)=0.81 (95%CI: 0.74 to 0.89; p<0.05), indicating a 19% lower prevalence of hospitalization for community-acquired pneumonia in the post-vaccination period.

CONCLUSIONS

The results suggest the effectiveness of the pneumococcal 10-valent conjugate vaccine in preventing severe cases of community-acquired pneumonia in children younger than one year of age.

Methods and challenges for the health impact assessment of vaccination programs in Latin America

OBJECTIVE

To describe methods and challenges faced in the health impact assessment of vaccination programs, focusing on the pneumococcal conjugate and rotavirus vaccines in Latin America and the Caribbean.

METHODS

For this narrative review, we searched for the terms “rotavirus”, “pneumococcal”, “conjugate vaccine”, “vaccination”, “program”, and “impact” in the databases Medline and LILACS. The search was extended to the grey literature in Google Scholar. No limits were defined for publication year. Original articles on the health impact assessment of pneumococcal and rotavirus vaccination programs in Latin America and the Caribbean in English, Spanish or Portuguese were included.

RESULTS

We identified 207 articles. After removing duplicates and assessing eligibility, we reviewed 33 studies, 25 focusing on rotavirus and eight on pneumococcal vaccination programs. The most frequent studies were ecological, with time series analysis or comparing pre- and post-vaccination periods. The main data sources were: health information systems; population-, sentinel- or laboratory-based surveillance systems; statistics reports; and medical records from one or few health care services. Few studies used primary data. Hospitalization and death were the main outcomes assessed.

CONCLUSIONS

Over the last years, a significant number of health impact assessments of pneumococcal and rotavirus vaccination programs have been conducted in Latin America and the Caribbean. These studies were carried out few years after the programs were implemented, meet the basic methodological requirements and suggest positive health impact. Future assessments should consider methodological issues and challenges arisen in these first studies conducted in the region.

Surveillance of the impact of pneumococcal conjugate vaccines in developing countries

Infection due to Streptococcus pneumoniae is a leading cause of morbidity and mortality in young children, especially in developing countries. With the support of Gavi, the Vaccine Alliance, the majority of these countries have introduced pneumococcal conjugate vaccines (PCV) into their national immunization programs and early data demonstrate a high degree of effectiveness, translating to enormous public health benefit through both direct and indirect (herd) effects. Future vaccination strategy may be focused on maintaining herd effects rather than individual protection. Evaluation of vaccine-type carriage, particularly in pneumonia cases, may be an easy, feasible way of measuring continued vaccine impact.