Effectiveness of Six Improved Cookstoves in Reducing Household Air Pollution and Their Acceptability in Rural Western Kenya.

BACKGROUND: Household air pollution (HAP) from biomass fuel burning is linked to poor health outcomes. Improved biomass cookstoves (ICS) have the potential to improve HAP. OBJECTIVES: A pre-/post- intervention study assessed the impact of six ICS on indoor air quality and acceptability of ICS to local users in rural Western Kenya. METHODS: We measured mean personal and kitchen level concentrations of particulate matter <2.5µm in diameter (PM2.5, µg/m3) and carbon monoxide (CO, ppm) during the 48-hour period of each ICS use in 45 households. We compared these levels to those observed with traditional 3-stone fire (TSF) use. We assessed ICS acceptability through interviews and focus groups. We evaluated association of stove type, fuel use, and factors related to cooking practices with mean kitchen PM2.5 and CO using multivariable regression. RESULTS: Stove type, exclusive ICS use (vs. concurrent TSF use), and the amount of fuel used were independently associated with kitchen PM2.5 and CO levels. Reductions (95%CI) in mean PM2.5 compared to TSF, ranged by ICS from 11.9% (-2.8-24.5) to 42.3% (32.3-50.8). Reductions in kitchen CO compared to TSF, ranged by ICS from -5.8% (-21.9-8.2) to 34.5% (23.2-44.1). Mean kitchen PM2.5 ranged from 319µg/m3 to 518µg/m3 by ICS. Women thought ICS were easy to use, more efficient, produced less smoke, and cooked faster, compared to TSF. Women also reported limitations for each ICS. CONCLUSIONS: We documented reductions in HAP from ICS compared to TSF. The PM2.5 levels with ICS use were still considerably higher than WHO indoor air quality guidelines. Achieving maximal potential of ICS requires adherence to more exclusive use and addressing user reported ICS limitations.

User Perspectives of Characteristics of Improved Cookstoves from a Field Evaluation in Western Kenya.

Over half of the world's population uses biomass fuels; these households cook on open fires indoors, increasing their risk of adverse health effects due to household air pollution (HAP) from biomass combustion. This study evaluated six improved cookstoves (ICS) for effectiveness and acceptability in a rural community in Western Kenya. This paper describes women's views on each ICS compared to the traditional three-stone fire. Views on stove characteristics, fuel consumption, health effects and acceptability were assessed through structured interviews and focus group discussions. Data were coded and analyzed using a thematic approach. In total, 262 interviews and 11 focus groups were conducted from 43 women. Overall, women preferred the ICS over the traditional three-stone fire for various reasons including ease of use, efficiency, fuel efficiency and perceived reduction in smoke and improved health. However, there were clear preferences for specific ICS with almost half of women preferring a Philips stove. Despite acceptance and use of ICS, women used multiple stoves to meet their daily needs. Qualitative studies are essential to field evaluations to provide insight into user perspectives and acceptability of ICS and to inform research and development of technologies that are both effective in reducing HAP and practical in use.

Systematic review of the effect of pneumococcal conjugate vaccine dosing schedules on vaccine-type invasive pneumococcal disease among young children.

BACKGROUND: Pneumococcal conjugate vaccines (PCV) are being implemented globally using a variety of different schedules. The optimal schedule to maximize protection of vaccinated children against vaccine-type invasive pneumococcal disease (VT-IPD) is not known. METHODS: To assess the relative benefit of various PCV dosing schedules, we conducted a systematic review of studies published in English from 1994 to 2010 (supplemented post hoc with studies from 2011) on PCV effectiveness against VT-IPD among children targeted to receive vaccine. Data on 2-dose and 3-dose primary series, both with and without a booster ("2+0," "2+1," "3+0" and "3+1"), were included. For observational studies using surveillance data or case counts, we calculated percentage reduction in VT-IPD before and after PCV introduction. RESULTS: Of 4 randomized controlled trials and 31 observational studies reporting VT-IPD among young children, none evaluated a 2+0 complete series, 7 (19%) evaluated 2+1, 4 (11%) 3+0 and 27 (75%) 3+1. Most (86%) studies were from North America or Europe. Only 1 study (observational) directly compared 2 schedules (3+0 vs. 3+1); results supported the use of a booster dose. In clinical trials, vaccine efficacy ranged from 65% to 71% with 3+0 and 83% to 94% with 3+1. Surveillance data and case counts demonstrate reductions in VT-IPD of up to 100% with 2+1 (6 studies) or 3+1 (17 studies) schedules and up to 90% with 3+0 (2 studies). Reductions were observed as early as 1 year after PCV introduction. CONCLUSIONS: These data support the use of 2+1, 3+0 and 3+1 schedules, although most data of PCV impact on VT-IPD among young children are from high-income countries using 3+1. Differences between schedules for impact on VT-IPD are difficult to discern based on available data.

Systematic review of the effect of pneumococcal conjugate vaccine dosing schedules on immunogenicity.

BACKGROUND: Despite the breadth of studies demonstrating benefits of pneumococcal conjugate vaccine (PCV), uncertainty remains regarding the optimal PCV dosing schedule in infants. METHODS: We conducted a systematic literature review of PCV immunogenicity published from 1994 to 2010 (supplemented post hoc with studies from 2011). Studies included for analysis evaluated ≥2 doses of 7-valent or higher product (excluding Aventis-Pasteur PCV11) administered to nonhigh-risk infants ≤6 months of age. Impact of PCV schedule on geometric mean antibody concentration (GMC) and proportion of subjects over 0.35 mcg/mL were assessed at various time points; the GMC 1 month postdose 3 (for various dosing regimens) for serotypes 1, 5, 6B, 14, 19F and 23F was assessed in detail using random effects linear regression, adjusted for product, acellular diphtheria-tetanus-pertussis/whole-cell diphtheria- tetanus-pertussis coadministration, laboratory method, age at first dose and geographic region. RESULTS: From 61 studies, we evaluated 13 two-dose (2+0) and 65 three-dose primary schedules (3+0) without a booster dose, 11 "2+1" (2 primary plus booster) and 42 "3+1" schedules. The GMC after the primary series was higher following 3-dose schedules compared with 2-dose schedules for all serotypes except for serotype 1. Pre- and postbooster GMCs were generally similar regardless of whether 2 or 3 primary doses were given. GMCs were significantly higher for all serotypes when dose 3 was administered in the second year (2+1) compared with ≤6 months of age (3+0). CONCLUSIONS: While giving the third dose in the second year of life produces a higher antibody response than when given as part of the primary series in the first 6 months, the lower GMC between the 2-dose primary series and booster may result in less disease protection for infants in that interval than those who completed the 3-dose primary series. Theoretical advantages of higher antibodies induced by giving the third dose in the second year of life, such as increased protection against serotype 1 disease, longer duration of protection or more rapid induction of herd effects, need to be evaluated in practice.

The differential impact of coadministered vaccines, geographic region, vaccine product and other covariates on pneumococcal conjugate vaccine immunogenicity.

BACKGROUND: Antipneumococcal capsular polysaccharide antibody concentrations are used as predictors of vaccine efficacy against vaccine serotype (ST) pneumococcal disease among infants. While pneumococcal conjugate vaccines (PCV) are recommended globally, factors associated with optimal PCV immune response are not well described. We aimed to systematically assess local setting factors, beyond dosing schedule, which may affect PCV antibody levels. METHODS: We conducted a literature review of PCV immunogenicity, abstracting data from published reports, unpublished sources, and conference abstracts from 1994 to 2010 (and ad hoc 2011 reports). Studies included in this analysis evaluated ≥ 2 primary doses of PCV before 6 months of age in non-high-risk populations, used 7-valent or higher PCV products (excluding Aventis-Pasteur and Merck products) and provided information on geometric mean concentration (GMC) for STs 1, 5, 6B, 14, 19F or 23F. Using random effects meta-regression, we assessed the impact of geographic region, coadministered vaccines and PCV product on postprimary GMC, adjusting for dosing schedule and ELISA laboratory method. RESULTS: Of 12,980 citations reviewed, we identified 103 vaccine study arms for this analysis. Children in studies from Asia, Africa and Latin America had significantly higher GMC responses compared with those in studies from Europe and North America. Coadministration with acellular pertussis DTP compared with whole-cell DTP had no effect on PCV immunogenicity except for ST14, where GMCs were higher when coadministered with acellular pertussis DTP. Vaccine product, number of PCV doses, dosing interval, age at first dose and ELISA laboratory method also affected the GMC. CONCLUSIONS: PCV immunogenicity is associated with geographic region and vaccine product; however, the associations and magnitude varied by ST. Consideration of these factors is essential when comparing PCV immunogenicity results between groups and should be included in the evidence base when selecting optimal PCV vaccine schedules in specific settings.

Systematic review of the effect of pneumococcal conjugate vaccine dosing schedules on prevention of pneumonia.

BACKGROUND: Pneumonia is the leading cause of morbidity and mortality among children <5 years of age globally. Pneumococcal conjugate vaccines (PCVs) are known to provide protection against vaccine serotype pneumococcal pneumonia; uncertainty exists regarding the optimum PCV dosing schedule. METHODS: We conducted a systematic review of studies published from 1994 to 2010 (supplemented post hoc with studies from 2011) documenting the effect of PCV dosing schedules on clinical and radiologically confirmed pneumonia, pneumococcal pneumonia and empyema among children of ages targeted to receive vaccine. Data on 2- and 3-dose schedules were included. Percent change of pneumonia incidence rates from baseline to most recent year post-PCV introduction was calculated. RESULTS: We identified 42 primary citations that evaluated PCV schedules and pneumonia. Thirty-seven (88%) were from North America, Europe or Australia; 37 (88%) evaluated PCV7 and 1 (2%) PCV10. Two studies (both observational) compared multiple schedules within the study. We found evidence of reduced clinical and radiologically confirmed pneumonia incidence for all schedules, including 2+1 (1 nonrandomized trial, 5 observational studies), 3+0 (5 randomized trials, 2 observational studies) and 3+1 (5 clinical trials, 24 observational studies) schedules. The magnitude of disease impact did not differ among schedules. Evidence for impact on pneumococcal pneumonia and empyema varied. CONCLUSIONS: All schedules (2+1, 3+0 and 3+1) reduced clinical and radiologically confirmed pneumonia. Quantifying differences in pneumonia disease impact between schedules was difficult due to heterogeneity among studies in design, case definition and population. These findings support World Health Organization recommendations for 3-dose schedules administered as either 3+0 or 2+1 regimens. Pneumonia impact data are still needed on expanded serotype PCV products, developing country settings and the role for a booster dose.

Systematic review of the effect of pneumococcal conjugate vaccine dosing schedules on vaccine-type nasopharyngeal carriage.

BACKGROUND: Pneumococcal conjugate vaccines (PCV) reduce nasopharyngeal carriage of vaccine type (VT) pneumococci, an important driver of vaccine programs' overall benefits. The dosing schedule that best reduces carriage is unclear. METHODS: We performed a systematic review of English language publications from 1994 to 2010 (supplemented post hoc with studies from 2011) reporting PCV effects on VT carriage to assess variability in effect by dosing schedule. RESULTS: We identified 32 relevant studies (36 citations) from 12,980 citations reviewed. Twenty-one (66%) evaluated PCV7; none used PCV10 or PCV13. Five studies evaluated 2 primary doses and 13 three primary doses. After the first year of life, 14 evaluated 3-dose primary series with PCV booster (3+1), seven 3 doses plus 23-valent polysaccharide booster "3+1PPV23," five "3+0," four "2+1," three "2+1PPV23" and two "2+0." Four studies directly compared schedules. From these, 3 primary doses reduced VT carriage more than 2 doses at 1-7 months following the series (1 study significant; 2 borderline). In a study, the 2+1 schedule reduced VT carriage more than 2+0 at 18, but not at 24 months of age. One study of a 23-valent pneumococcal polysaccharide vaccine booster showed no effect. All 16 clinical trials with unvaccinated controls and 11 observational studies with before-after designs showed reduction in VT carriage. CONCLUSIONS: The available literature demonstrates VT-carriage reduction for 2+0, 2+1, 3+0 and 3+1 PCV schedules, but not for 23-valent pneumococcal polysaccharide vaccine booster. Comparisons between schedules show that 3 primary doses and a 2+1 schedule may reduce carriage more than 2 primary doses and a 2+0 schedule, respectively.

Systematic review of the indirect effect of pneumococcal conjugate vaccine dosing schedules on pneumococcal disease and colonization.

BACKGROUND: To aid decision making for pneumococcal conjugate vaccine (PCV) use in infant national immunization programs, we summarized the indirect effects of PCV on clinical outcomes among nontargeted age groups. METHODS: We systematically reviewed the English literature on infant PCV dosing schedules published from 1994 to 2010 (with ad hoc addition of 2011 articles) for outcomes on children >5 years of age and adults including vaccine-type nasopharyngeal carriage (VT-NP), vaccine-type invasive pneumococcal disease (VT-IPD) and syndromic pneumonia. RESULTS: Of 12,980 citations reviewed, we identified 21 VT-IPD, 6 VT-NP and 9 pneumonia studies. Of these 36, 21 (58%) included 3 primary doses plus PCV or pneumococcal polysaccharide vaccine (PPV23) booster schedule (3+1 or 3+PPV23), 5 (14%) 3+0, 9 (25%) 2+1 and 1 (3%) 2+0. Most (95%) were PCV7 studies. Among observational VT-IPD studies, all schedules (2+1, 3+0 and 3+1) demonstrated reductions in incidence among young adult groups. Among syndromic pneumonia observational studies (2+1, 3+0 and 3+1), only 3+1 schedules showed significant indirect impact. Of 2 VT-NP controlled trials (3+0 and 3+1) and 3 VT-NP observational studies (2+1, 3+1 and 3+PPV23), 3+1 and 3+PPV23 schedules showed significant indirect effect. The 1 study to directly compare between schedules was a VT-NP study (2+0 vs. 2+1), which found no indirect effect on older siblings and parents of vaccinated children with either schedule. CONCLUSIONS: Indirect benefit of a 3+1 infant PCV dosing schedule has been demonstrated for VT-IPD, VT-NP and syndromic pneumonia; 2+1 and 3+0 schedules have demonstrated indirect effect only for VT-IPD. The choice of optimal infant PCV schedule is limited by data paucity on indirect effects, especially a lack of head-to-head studies and studies of PCV10 and PCV13.

Methods for a systematic review of pneumococcal conjugate vaccine dosing schedules.

BACKGROUND: Streptococcus pneumoniae causes a considerable amount of morbidity and mortality in children <5. However, pneumococcal conjugate vaccines (PCVs) can prevent much of this burden. Until recently, PCVs were mostly available only in developed countries using a variety of dosing schedules. As more lower income countries make decisions to introduce PCV into their national immunization programs, an optimal schedule with which to administer PCV has become a key policy question. METHODS: We performed a systematic review of English literature published from 1994 to 2010 on the effects of PCV dosing schedules on immunogenicity, nasopharyngeal carriage, invasive pneumococcal disease and pneumonia. Data were independently double abstracted and cleaned for analysis. Descriptive analyses were performed. RESULTS: We identified 12,980 citations from the literature search (12,976) and secondary means (44). Double review of titles and abstracts yielded 769 articles that underwent full data abstraction. Of these, 350 were further analyzed and are presented in separate reports in this supplement. CONCLUSIONS: This article presents the methods utilized in our systematic review. Because of the heterogenity of the study methods of the reports identified by this review, we did not conduct formal meta-analyses. However, these methods allow us to present a full landscape of the literature on PCV dosing schedules.

Serotype-specific changes in invasive pneumococcal disease after pneumococcal conjugate vaccine introduction: a pooled analysis of multiple surveillance sites.

BACKGROUND: Vaccine-serotype (VT) invasive pneumococcal disease (IPD) rates declined substantially following introduction of 7-valent pneumococcal conjugate vaccine (PCV7) into national immunization programs. Increases in non-vaccine-serotype (NVT) IPD rates occurred in some sites, presumably representing serotype replacement. We used a standardized approach to describe serotype-specific IPD changes among multiple sites after PCV7 introduction. METHODS AND FINDINGS: Of 32 IPD surveillance datasets received, we identified 21 eligible databases with rate data ≥ 2 years before and ≥ 1 year after PCV7 introduction. Expected annual rates of IPD absent PCV7 introduction were estimated by extrapolation using either Poisson regression modeling of pre-PCV7 rates or averaging pre-PCV7 rates. To estimate whether changes in rates had occurred following PCV7 introduction, we calculated site specific rate ratios by dividing observed by expected IPD rates for each post-PCV7 year. We calculated summary rate ratios (RRs) using random effects meta-analysis. For children <5 years old, overall IPD decreased by year 1 post-PCV7 (RR 0.55, 95% CI 0.46-0.65) and remained relatively stable through year 7 (RR 0.49, 95% CI 0.35-0.68). Point estimates for VT IPD decreased annually through year 7 (RR 0.03, 95% CI 0.01-0.10), while NVT IPD increased (year 7 RR 2.81, 95% CI 2.12-3.71). Among adults, decreases in overall IPD also occurred but were smaller and more variable by site than among children. At year 7 after introduction, significant reductions were observed (18-49 year-olds [RR 0.52, 95% CI 0.29-0.91], 50-64 year-olds [RR 0.84, 95% CI 0.77-0.93], and ≥ 65 year-olds [RR 0.74, 95% CI 0.58-0.95]). CONCLUSIONS: Consistent and significant decreases in both overall and VT IPD in children occurred quickly and were sustained for 7 years after PCV7 introduction, supporting use of PCVs. Increases in NVT IPD occurred in most sites, with variable magnitude. These findings may not represent the experience in low-income countries or the effects after introduction of higher valency PCVs. High-quality, population-based surveillance of serotype-specific IPD rates is needed to monitor vaccine impact as more countries, including low-income countries, introduce PCVs and as higher valency PCVs are used. Please see later in the article for the Editors' Summary.

"It is good for my family's health and cooks food in a way that my heart loves": qualitative findings and implications for scaling up an improved cookstove project in rural Kenya.

The use of indoor, three-stone fire pits in resource-poor countries is a substantial burden on human health and the environment. We conducted a pilot intervention promoting the purchase and use of an improved cookstove in rural Kenya. The goals of this qualitative inquiry were to understand the motivation to purchase and use; perceived benefits and challenges of cookstove use; and the most influential promotion activities for scaling up future cookstove promotion. Purposive sampling was used to recruit 10 cookstove promoters and 30 cookstove purchasers in the Luo community. Qualitative semi-structured interviews were transcribed and a thematic analysis conducted. Women reported the need for less firewood, fuel cost savings, reduced smoke, improved cooking efficiency, reduced eye irritation, lung congestion and coughing as major benefits of the cookstove. Cost appeared to be a barrier to wider adoption. The most persuasive promotion strategies were interpersonal communication through social networks and cooking demonstrations. Despite this cost barrier, many women still considered the improved cookstove to be a great asset within their household. This inquiry provided important guidance for future cookstove implementation projects.

Global use of Haemophilus influenzae type b conjugate vaccine.

Haemophilus influenzae type b (Hib) conjugate vaccines have been underutilized globally. We report progress in global use of Hib vaccines included in national immunization schedules. The number of countries using Hib vaccine increased from 89/193 (46%) in 2004 to 158/193 (82%) by the end of 2009. The increase was greatest among low-income countries eligible for financial support from the GAVI Alliance [13/75 (17%) in 2004, 60/72 (83%) by the end of 2009], and can be attributed to various factors. Additional efforts are still needed to increase vaccine adoption in lower middle income countries [20/31 (65%) by the end of 2009].