Rates of Acquisition of Pneumococcal Colonization and Transmission Probabilities, by Serotype, Among Newborn Infants in Kilifi District, Kenya (original) (raw)
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Journal of Infectious Diseases, 2012
Background. To understand and model the impact of pneumococcal conjugate vaccines at the population level, we need to know the transmission dynamics of individual pneumococcal serotypes. We estimated serotypespecific clearance and acquisition rates of nasopharyngeal colonization among Kenyan children. Methods. Children aged 3-59 months who were identified as carriers in a cross-sectional survey were followed-up approximately 1, 2, 4, 8, 16, and 32 days later and monthly thereafter until culture of 2 consecutive swabs yielded an alternative serotype or no pneumococcus. Serotype-specific clearance rates were estimated by exponential regression of interval-censored carriage durations. Duration was estimated as the reciprocal of the clearance rate, and acquisition rates were estimated on the basis of prevalence and duration, assuming an equilibrium state. Results. Of 2840 children sampled between October 2006 and December 2008, 1868 were carriers. The clearance rate was 0.032 episodes/day (95% confidence interval [CI], .030-.034), for a carriage duration of 31.3 days, and the rate varied by serotype (P < .0005). Carriage durations for the 28 serotypes with ≥10 carriers ranged from 6.7 to 50 days. Clearance rates increased with year of age, adjusted for serotype (hazard ratio, 1.21; 95% CI, 1.15-1.27). The acquisition rate was 0.061 episodes/day (95% CI, .055-.067), which did not vary with age. Serotypespecific acquisition rates varied from 0.0002 to 0.0022 episodes/day. Serotype-specific acquisition rates correlated with prevalence (r = 0.91; P < .00005) and with acquisition rates measured in a separate study involving 1404 newborns in Kilifi (r = 0.87; P < .00005). Conclusions. The large sample size and short swabbing intervals provide a precise description of the prevalence, duration, and acquisition of carriage of 28 pneumococcal serotypes. In Kilifi, young children experience approximately 8 episodes of carriage per year. The declining prevalence with age is attributable to increasing clearance rates.
The Prevalence and Risk Factors for Pneumococcal
2016
Background: Pneumococcal conjugate vaccines (PCV) reduce nasopharyngeal carriage of vaccine-serotype pneumococci but increase in the carriage of non-vaccine serotypes. We studied the epidemiology of carriage among children 3–59 months old before vaccine introduction in Kilifi, Kenya.
BMC infectious diseases, 2017
Pneumococci are spread by persons with nasopharyngeal colonization, a necessary precursor to invasive disease. Pneumococcal conjugate vaccines can prevent colonization with vaccine serotype strains. In 2011, Kenya became one of the first African countries to introduce the 10-valent pneumococcal conjugate vaccine (PCV10) into its national immunization program. Serial cross-sectional colonization surveys were conducted to assess baseline pneumococcal colonization, antibiotic resistance patterns, and factors associated with resistance. Annual surveys were conducted in one urban and one rural site during 2009 and 2010 among children aged <5 years. To reflect differences in vaccine target population, recruitment was age-stratified in Kibera, whereas a simple random sample of children was drawn in Lwak. Nasopharyngeal swabs were collected from eligible children. Pneumococci were isolated and serotyped. Antibiotic susceptibility testing was performed using the 2009 isolates. Antibiotic ...
International Journal of Infectious Diseases
Nasopharyngeal carriage of Streptococcus pneumoniae underpins disease development and transmission. This study was performed to examine pneumococcal carriage dynamics, including density and multiple serotype carriage, in Indonesian infants during the first year of life. Methods: Two hundred healthy infants were enrolled at 2 months of age. Eight nasopharyngeal swabs were collected from enrolment until 12 months of age. Pneumococci were detected using quantitative PCR and serotyped by microarray. Regression models assessed factors influencing pneumococcal carriage and density. Results: Eighty-five percent of infants carried pneumococci at least once during the study. The median age at first acquisition was 129 days (interquartile range 41-216 days). The median duration of carriage was longer for the first pneumococcal acquisition compared with subsequent acquisitions (151 days vs. 95 days, p < 0.0001). Of the 166 infants who carried pneumococci during the study, the majority (63.9%) carried a single pneumococcal serotype at a time. Pneumococcal carriage density was higher when upper respiratory tract infection symptoms were present, lower during antibiotic usage, decreased with age, and tended to decrease over time during a carriage episode. Conclusions: The majority of Indonesian infants carry pneumococcus at least once during the first year of life. Pneumococcal carriage is a dynamic process, with pneumococcal density varying during a carriage episode.
Journal of Global Health
Background Nasopharyngeal pneumococcal carriage (NPC) is a prerequisite for invasive pneumococcal disease and reduced carriage of vaccine serotypes is a marker for the protection offered by the pneumococcal conjugate vaccine (PCV). The present study reports NPC during the first year of life in a vaccinated (with PCV10) cohort in Bangladesh and an unvaccinated cohort in India. Methods A total of 450 and 459 infants were recruited from India and Bangladesh respectively within 0-7 days after birth. Nasopharyngeal swabs were collected at baseline, 18 and 36 weeks after birth. The swabs were processed for pneumococcal culture and identification of serotypes by the Quellung test and polymerase chain reaction (PCR). An identical protocol was applied at both sites. Results Prevalence of NPC was 48% in the Indian and 54.8% in the Bangladeshi cohort at 18 weeks. It increased to 53% and 64.8% respectively at 36 weeks. The average prevalence of vaccine serotypes was higher in the Indian cohort (17.8% vs 9.8% for PCV-10 and 26.1% vs17.6% for PCV-13) with 6A, 6B, 19F, 23F, and 19A as the common serotypes. On the other hand, the prevalence of non-vaccine serotypes was higher (43.6% vs 27.1% for non-PCV13) in the Bangladeshi cohort with 34, 15B, 17F, and 35B as the common serotypes. Overcrowding was associated with increased risk of pneumococcal carriage. The present PCV-13 vaccine would cover 28%-30% and 47%-48% serotypes in the Bangladeshi and Indian cohorts respectively. Conclusions South Asian infants get colonised with pneumococci early in infancy; predominantly vaccine serotypes in PCV naïve population (India) and non-vaccine serotypes in the vaccinated population (Bangladesh). These local findings are important to inform the public health policy and the development of higher valent pneumococcal vaccines.
2021
BackgroundInvasive pneumococcal disease (IPD) in young infants is uncommon but associated with high morbidity and mortality. Accurate data on the burden of IPD in young infants in low-income countries are lacking. We examined the burden of IPD in infants aged <90 days in Blantyre, Malawi over a 14 year period and evaluated the impact of the 12 November 2011 introduction of the 13-valent pneumococcal conjugate vaccine (PCV13) on vaccine-serotype IPD (VT-IPD) in this population.MethodsWe conducted laboratory-based prospective IPD surveillance in infants aged <90 days admitted to Queen Elizabeth Central Hospital (QECH) in Blantyre between 2005 and 2018, including 7 years pre- and 7 years post-PCV13 introduction. IPD was defined as Streptococcus pneumoniae identified by culture from blood or cerebrospinal fluid. Serotypes were determined by multiplex PCR and latex agglutination testing.ResultsWe identified 130 cases of culture-confirmed IPD in infants <90 days old between 2005-...
Journal of Infectious Diseases, 1996
Nasopharyngeal carriage of Streptococcus pneumoniae was studied in 162 healthy infants at ages 2, 4, 6, 7, 12, and 13 months and in an additional 352 healthy children at ages 12, 15, 18, 21, and 24 months. Carriage was 26%,39%, and 62% at 2, 12, and 24 months, respectively, and the respective resistance to ;:.1 antibiotic was 11%, 19%, and 27%. The presence of an older sibling or antibiotic treatment during the month preceding the culture was associated with carriage of resistant pneumococci in infants, whereas attendance at large day care centers was associated with carriage during the second year of life. Antibiotic resistance was detected in all 7 serotypes included in the candidate pediatric conjugate vaccines and was significantly more prevalent among vaccine-type pneumococci than among non -vaccine-type pneumococci. The use of conjugate vaccines may reduce the spread of resistant pneumococci.
Clinical Infectious Diseases, 2001
During 1 decade (1989-1998), data on invasive pneumococcal disease were collected prospectively to assess the burden of disease among Jewish and Bedouin children in southern Israel and the potential reduction in illness that can be achieved by using conjugate vaccines. Data on 513 children <15 years old with bacteriologically proven invasive pneumococcal disease were obtained. Among Jewish and Bedouin children <5 years old, incidence rates were 45 and 139 cases per 100,000 child-years of observation, respectively. Jewish and Bedouin children differed in clinical manifestations, seasonal patterns of disease, serotype distribution, and antibiotic susceptibility rates. The potential coverage by 7-, 9-, and 11-valent conjugate vaccines is 41%, 67%, and 71%, respectively, for Jewish children and 22%, 63%, and 65%, respectively, for Bedouin children. The 9- and 11-valent pneumococcal conjugate vaccines have the potential to substantially decrease invasive pneumococcal disease in southern Israel.