Effectiveness of the 10-Valent Pneumococcal Conjugate Vaccine (PCV-10) in Children in Chile: A Nested Case-Control Study Using Nationwide Pneumonia Morbidity and Mortality Surveillance Data

Background

The ten-valent pneumococcal conjugate vaccine (PCV10) was introduced into the Chilean National Immunization Program (NIP) in January 2011 with a 3+1 schedule (2, 4, 6 and 12 months) without catch-up vaccination. We evaluated the effectiveness of PCV10 on pneumonia morbidity and mortality among infants during the first two years after vaccine introduction.

Methods

This is a population-based nested case-control study using four merged nationwide case-based electronic health data registries: live birth, vaccination, hospitalization and mortality. Children born in 2010 and 2011 were followed from two moths of age for a period of two years. Using four different case definitions of pneumonia hospitalization and/or mortality (all-cause and pneumonia related deaths), all cases and four randomly selected matched controls per case were selected. Controls were matched to cases on analysis time. Vaccination status was then assessed. Vaccine effectiveness (VE) was estimated using conditional logistic regression.

Results

There were a total of 497,996 children in the 2010 and 2011 Chilean live-birth cohorts. PCV10 VE was 11.2% (95%CI 8.5–13.6) when all pneumonia hospitalizations and deaths were used to define cases. VE increased to 20.7 (95%CI 17.3–23.8) when ICD10 codes used to denote viral pneumonia were excluded from the case definition. VE estimates on pneumonia deaths and all-cause deaths were 71.5 (95%CI 9.0–91.8) and 34.8 (95% CI 23.7–44.4), respectively.

Conclusion

PCV10 vaccination substantially reduced the number of hospitalizations due to pneumonia and deaths due to pneumonia and to all-causes over this study period. Our findings also reinforce the importance of having quality health information systems for measuring VE.

Prevalence of meningococcal carriage in children and adolescents aged 10-19 years in Chile in 2013

In 2011, Chile experienced an increase in the number of cases of IMD caused by Neisseria meningitidis group W. This epidemiological scenario prompted authorities to implement prevention strategies. As part of these strategies, the Institute of Public Heath of Chile conducted a cross-sectional study to determine the prevalence of pharyngeal carriage of N. meningitidis in a representative sample of healthy children and adolescents aged 10-19 years. The identification of presumptive N. meningitidis strains was performed by testing carbohydrate utilization in the National Reference Laboratory at the ISP. Association of meningococcal carriage with risk factors was analyzed by calculating the Odds Ratio. Selected variables were included in a logistic model for risk analyses. The prevalence of carriage of N. meningitidis was 6.5% (CI: 5.7-7.3%). Older age (carriers: 14.2±0.29 vs. non-carriers: 13.8±0.08 years old; p=0.009), cohabitation with children (carriers: 0.9±0.13 vs. non-carriers: 0.7±0.03; p=0.028), number of smoking cohabitants (carriers: 0.55±0.13 vs. non-carriers: 0.44±0.03) and frequent attendance to crowded social venues (carriers: 49% vs. non-carriers: 37%; p=0.008) were determined to favor carriage. Statistical modeling showed that meningococcal carriage was associated with older age (OR: 1.077, p-value: 0.002) and cohabitation with children (OR: 1.182, p-value: 0.02).

[Laboratory surveillance for invasive meningococcal disease in Chile, 2006-2012]

BACKGROUND

Laboratory surveillance of Invasive Meningococcal Disease (IMD) is performed by the Institute of Public Health of Chile. It confirms identification, classifies in serogroups and analyzes the genetic profiles of Neisseria meningitidis isolates from laboratories throughout the country.

AIM

To show the results of this surveillance from 2006 to 2012.

METHODS

A descriptive data analysis of the confirmed cases of IMD and serological characterization, susceptibility and genetic profiles of the isolates. The analysis was disaggregated by serogroup, age and region.

RESULTS

From 2006 to 2012, 486 isolates of N. meningitidis were confirmed. In 2011 a rise in IMD rates was observed due to an increase in W serogroup cases, mainly affecting children aged 5 years or less. Serogroup W became the most prevalent during 2012 (58.3%), replacing the historically prevalent serogroup B. Predominating strains belonged to ST-32 complex/ET-5 complex (40, 4% of strains) and ST-41/44 complex/ Lineage 3 (45, 9% of strains).

CONCLUSIONS

Laboratory surveillance has allowed the early detection of increasing IMD caused by serogroup W, which is emergent in Chile. This information has reinforced the daily monitoring of new cases, in collaboration with all the clinical laboratories of the country.

[Laboratory surveillance of Streptococcus pneumoniae from invasive disease, Chile 2007-2012]

BACKGROUND

10-valent pneumococcal vaccine (PCV-10) was introduced in 2011 to the National Immunization Program in Chile. It was administered in 4 doses, but in 2012 it was modified to a 3 dose program. This article shows the results of the Laboratory Surveillance System for Streptococcus pneumoniae isolated of invasive disease from 2007 to 2012 and compares the incidence of invasive pneumococcal disease (IPD) by age groups in the prevaccinal (2007-2010) and postvaccinal period (2012).

METHODS

Descriptive study of S. pneumoniae surveillance in invasive diseases cases confirmed at the National Reference Laboratory of the Institute of Public Health of Chile from 2007 to 2012.

RESULTS

Global incidence of laboratory confirmed IPD cases decreased 27.8% from 2007 to 2012 and showed a lower risk for IPD in 2012 compared with 2007. Incidence in children aged 1 year or less decreased from 56.1 to 16.3 per 100,000 and from 42.0 to 19.9 per 100,000 in children aged 12 to 23 months in the same period. Highest decreases were observed in IPD cases caused by serotypes 4 (100%), 19F (93.3%), 23F (90.9%), 14 (81.1%), 6B (70%), 18C (58.3%) and 1(81.8%) in children aged 2 years or less.

CONCLUSION

Surveillance System detects S.pneumoniae isolated from invasive diseases, contributing with information about laboratory confirmed IPD trends, prevalent serotypes and replacement effects. These results can be used as evidence in healthcare decision making for pneumococcal vaccines.

[Prevalence of leptospirosis in adults in Chile, 2003]

BACKGROUND

Leptospirosis is a zoonosis endemic in some regions in Chile. Since its inclusion into the list of notifiable diseases, the Chilean Ministry of Health was able to maintain an adequate surveillance of leptospirosis. Nonetheless, some cases are not reported due to subclinical disease or nonspecific symptoms.

OBJECTIVES

Determine the national prevalence of leptospirosis and assess the epidemiological characteristics of seropositive individuals.

METHODS

Secondary data analysis of the National Health Survey, 2003.

RESULTS

National prevalence was 0.4%. Low socioeconomical status and female gender were characteristics, which were more frequently found in sero-positive cases. The most common serovars were icterohaemorrhagiae, bratislava and pomona.

CONCLUSION

We present the first epidemiological analysis of leptospirosis on a national level in Chile. Thus, the study contributes to the knowledge the epidemiological situation of this disease in Chile.