Acta Pædiatrica ISSN 0803-5253
REGULAR ARTICLE
Pertussis is still common in a highly vaccinated infant population Elettra Berti1, Elena Chiappini ([email protected])1, Elisa Orlandini2, Luisa Galli1, Maurizio de Martino1 1.Department of Sciences for Health Sciences, Anna Meyer Children’s University Hospital, University of Florence, Florence, Italy 2.Information Technology Section, Tuscany Regional Government Department of Right to Health and Solidarity Policies, Florence, Italy
Keywords Children, Epidemiology, Hospitalisation, Infants, Pertussis
ABSTRACT Aim: To provide epidemiological data on pertussis in a highly vaccinated paediatric
Correspondence Elena Chiappini, MD, Department of Sciences for Health Sciences, Anna Meyer Children’s University Hospital, University of Florence, Viale Pieraccini 24, 50100 Florence, Italy. Tel: +39 055 5662830 | Fax: +39 055 4221012 | Email: [email protected]
Methods: We analysed data from the regional hospital discharge database on children
Received 10 October 2013; revised 8 February 2014; accepted 7 April 2014. DOI:10.1111/apa.12655
population, focusing on the age of the infected children. hospitalised for pertussis in Tuscany, Italy, from January 2000 to December 2012.
Results: A total of 279 cases were recorded. The majority of hospitalised children were infants (75.6%), who had the highest rate of complications (24.2%) of any age group and a crude mortality rate of 9.47 per 1000. The overall hospitalisation rate decreased significantly during the study period, from 4.23 to 2.82 per 100 000, but when we analysed the data by age groups, we found notable differences. Hospitalisation rates in the 1- to 4-year-old age group decreased significantly from 2.82 in the year 2000 to zero per 100 000 in 2012 and decreased significantly in the 5- to 9-year-old age group over the same period, from 6.58 to 0.63 per 100 000. Overall hospitalisation rates in the infant group remained high at 53.14 per 100 000, with three peaks due to periodic pertussis outbreaks. Conclusion: Pertussis is still a relevant health concern in infants who are unvaccinated or incompletely immunised, both in terms of morbidity and mortality.
INTRODUCTION Pertussis is a worldwide, endemic, epidemic, infectious respiratory disease, with outbreaks every three to 5 years. Despite universal immunisation programmes and high vaccination coverage, pertussis remains a major public health issue in Western countries. A resurgence of the disease has been recorded in many developed countries in the last decade, affecting mainly infants and adolescents (1– 7). Moreover, pertussis is still an important cause of death in infants, with a mortality rate of 0.2% in children under the age of 6 months (1). In Italy, pertussis immunisation has been recommended since the 1960s and relevant epidemiology changes have been described during the past few decades, according to the rate of coverage (7,8). However, a re-emergence of pertussis has been reported in the last few years, even in our country, despite the high vaccination coverage (7–9). Since the 1990s, acellular pertussis vaccines have been introduced to the Italian vaccination schedules. In Tuscany, these particular vaccines are administered to infants when they reach the ages of 3, 5, 11–13 months and 5–6 years. Since 2003, a booster dose has been provided for adolescents aged from 12 to 14. The aim of the study was to evaluate the incidence of pertussis in a highly vaccinated paediatric population, together with the relevant changes over a 13-year period, focusing on age, pertussis-related complications and mortality.
846
METHODS Study design and case definition We performed a retrospective cohort study analysing children hospitalised for pertussis in 31 Tuscan hospitals, from January 1, 2000 to December 31, 2012. Cases were identified by consulting the regional hospital discharge database, which is coded according to the International Classification of Disease, Ninth Revision, Clinical Modification (ICD-9-CM) system that is currently used in Italy (10). The regional database was retrospectively searched using the following ICD9-CM codes: 033.0 (pertussis due to Bordetella pertussis), 033.1 (pertussis due to Bordetella parapertussis), 033.8 (pertussis due to other specified pathogens), 033.9 (pertussis due to unspecified pathogens) and 484.3 (pneumonia in pertussis).
Key notes
There were 279 children hospitalised for pertussis in Tuscany, Italy, from January 2000 to December 2012 and 75.6% were infants. Pertussis-related hospital admissions fell in the most highly vaccinated age groups, but not in children under the age of one or over the age of nine. Pertussis remained endemic in the region’s infants, was an important cause of hospitalisation and resulted in a crude mortality rate of 9.47 per 1000.
©2014 Foundation Acta Pædiatrica. Published by John Wiley & Sons Ltd 2014 103, pp. 846–849
Pertussis in infants
Berti et al.
Hospitalised children below the age of 18 years, living in Tuscany and discharged from a Tuscan hospital with a diagnosis of pertussis were included in the study. Cases were selected if the pertussis diagnosis code occurred in any of the diagnostic discharge reports. A double-check using any data written up on the enrolled children was also conducted to avoid possible bias due to the inpatients being transferred between hospitals. Data collection All data on paediatric pertussis-related hospitalisations were analysed by consulting the hospital discharge form from the regional database. Cases were defined as complicated if they had the pertussis discharge code and any other pertussis complication in any diagnostic position. The following codes were included: pneumonia (ICD-482.9, 484.3, 485.0 and 486.0), acute bronchiolitis (ICD-4661), respiratory failure (ICD-5188.1 and 5188.2), syncope (ICD7802), sepsis (ICD-7855.2) and rib fracture (ICD-8070.0). The Italian National Statistical Institute database provided the number of children living in Tuscany, by age group, during the study period. We also collected surveillance data about vaccination coverage for pertussis at 24 months of age, from January 1, 2000 to December 31, 2012. The study was approved by the ethics committee of the Anna Meyer Children’s University Hospital in Florence, Italy. Statistical analysis The study population was characterised on the basis of age, gender, nationality, the season when the child was hospitalised, the presence of complications, hospital admitting, median length of stay and mode of discharge. Patients were stratified by four age groups: 0–11 months, 12 months to 4 years, 5–9 years and 10–17 years. Rates of hospitalisation for pertussis were calculated as cases per 100 000 children living in Tuscany, and the 95% confidence intervals (CI) were calculated using an exact binomial distribution. Categorical variables were analysed using the v2 or the v2 for trend tests (Cochran–Armitage test for trend). All significant tests were two sided. We considered a value of p < 0.05 significant. The statistical analyses were performed using the SPSS software package (SPSS 11.5; Chicago, IL, USA).
RESULTS During the study period, 279 children were hospitalised for pertussis by the 31 Tuscan hospitals in the region, and the characteristics of the study population are summarised in Table S1. Median age was 3 months, and the interquartile range (IQR) was 1–11. More than three-quarters (75.63%) of the 279 hospitalisations occurred in the zero- to 11month age group, and 62% of the subjects studied were children in their first 3 months of life, who had not yet started the immunisation schedule. The infant group also presented with the highest rate of pertussis-related complications (51 of 211, 24.17%) of any age group, as reported in Figure 1. Pneumonia was the main complication in this age
Figure 1 Pertussis: cases and complications by age group in Tuscan children from 2000 to 2012.
group (32 of 211), followed by respiratory failure (11 of 211), acute bronchiolitis (6 of 211), sepsis (1 of 211) and syncope (1 of 211). Two of 279 children died during hospitalisation, providing a crude mortality rate of 7.17 per 1000 children (95% CI: 4.14–101.95) and a case fatality rate of 9.47 per 1000 infants (95% CI: 5.56–134.31). Both children were female and aged
REGULAR ARTICLE
Pertussis is still common in a highly vaccinated infant population Elettra Berti1, Elena Chiappini ([email protected])1, Elisa Orlandini2, Luisa Galli1, Maurizio de Martino1 1.Department of Sciences for Health Sciences, Anna Meyer Children’s University Hospital, University of Florence, Florence, Italy 2.Information Technology Section, Tuscany Regional Government Department of Right to Health and Solidarity Policies, Florence, Italy
Keywords Children, Epidemiology, Hospitalisation, Infants, Pertussis
ABSTRACT Aim: To provide epidemiological data on pertussis in a highly vaccinated paediatric
Correspondence Elena Chiappini, MD, Department of Sciences for Health Sciences, Anna Meyer Children’s University Hospital, University of Florence, Viale Pieraccini 24, 50100 Florence, Italy. Tel: +39 055 5662830 | Fax: +39 055 4221012 | Email: [email protected]
Methods: We analysed data from the regional hospital discharge database on children
Received 10 October 2013; revised 8 February 2014; accepted 7 April 2014. DOI:10.1111/apa.12655
population, focusing on the age of the infected children. hospitalised for pertussis in Tuscany, Italy, from January 2000 to December 2012.
Results: A total of 279 cases were recorded. The majority of hospitalised children were infants (75.6%), who had the highest rate of complications (24.2%) of any age group and a crude mortality rate of 9.47 per 1000. The overall hospitalisation rate decreased significantly during the study period, from 4.23 to 2.82 per 100 000, but when we analysed the data by age groups, we found notable differences. Hospitalisation rates in the 1- to 4-year-old age group decreased significantly from 2.82 in the year 2000 to zero per 100 000 in 2012 and decreased significantly in the 5- to 9-year-old age group over the same period, from 6.58 to 0.63 per 100 000. Overall hospitalisation rates in the infant group remained high at 53.14 per 100 000, with three peaks due to periodic pertussis outbreaks. Conclusion: Pertussis is still a relevant health concern in infants who are unvaccinated or incompletely immunised, both in terms of morbidity and mortality.
INTRODUCTION Pertussis is a worldwide, endemic, epidemic, infectious respiratory disease, with outbreaks every three to 5 years. Despite universal immunisation programmes and high vaccination coverage, pertussis remains a major public health issue in Western countries. A resurgence of the disease has been recorded in many developed countries in the last decade, affecting mainly infants and adolescents (1– 7). Moreover, pertussis is still an important cause of death in infants, with a mortality rate of 0.2% in children under the age of 6 months (1). In Italy, pertussis immunisation has been recommended since the 1960s and relevant epidemiology changes have been described during the past few decades, according to the rate of coverage (7,8). However, a re-emergence of pertussis has been reported in the last few years, even in our country, despite the high vaccination coverage (7–9). Since the 1990s, acellular pertussis vaccines have been introduced to the Italian vaccination schedules. In Tuscany, these particular vaccines are administered to infants when they reach the ages of 3, 5, 11–13 months and 5–6 years. Since 2003, a booster dose has been provided for adolescents aged from 12 to 14. The aim of the study was to evaluate the incidence of pertussis in a highly vaccinated paediatric population, together with the relevant changes over a 13-year period, focusing on age, pertussis-related complications and mortality.
846
METHODS Study design and case definition We performed a retrospective cohort study analysing children hospitalised for pertussis in 31 Tuscan hospitals, from January 1, 2000 to December 31, 2012. Cases were identified by consulting the regional hospital discharge database, which is coded according to the International Classification of Disease, Ninth Revision, Clinical Modification (ICD-9-CM) system that is currently used in Italy (10). The regional database was retrospectively searched using the following ICD9-CM codes: 033.0 (pertussis due to Bordetella pertussis), 033.1 (pertussis due to Bordetella parapertussis), 033.8 (pertussis due to other specified pathogens), 033.9 (pertussis due to unspecified pathogens) and 484.3 (pneumonia in pertussis).
Key notes
There were 279 children hospitalised for pertussis in Tuscany, Italy, from January 2000 to December 2012 and 75.6% were infants. Pertussis-related hospital admissions fell in the most highly vaccinated age groups, but not in children under the age of one or over the age of nine. Pertussis remained endemic in the region’s infants, was an important cause of hospitalisation and resulted in a crude mortality rate of 9.47 per 1000.
©2014 Foundation Acta Pædiatrica. Published by John Wiley & Sons Ltd 2014 103, pp. 846–849
Pertussis in infants
Berti et al.
Hospitalised children below the age of 18 years, living in Tuscany and discharged from a Tuscan hospital with a diagnosis of pertussis were included in the study. Cases were selected if the pertussis diagnosis code occurred in any of the diagnostic discharge reports. A double-check using any data written up on the enrolled children was also conducted to avoid possible bias due to the inpatients being transferred between hospitals. Data collection All data on paediatric pertussis-related hospitalisations were analysed by consulting the hospital discharge form from the regional database. Cases were defined as complicated if they had the pertussis discharge code and any other pertussis complication in any diagnostic position. The following codes were included: pneumonia (ICD-482.9, 484.3, 485.0 and 486.0), acute bronchiolitis (ICD-4661), respiratory failure (ICD-5188.1 and 5188.2), syncope (ICD7802), sepsis (ICD-7855.2) and rib fracture (ICD-8070.0). The Italian National Statistical Institute database provided the number of children living in Tuscany, by age group, during the study period. We also collected surveillance data about vaccination coverage for pertussis at 24 months of age, from January 1, 2000 to December 31, 2012. The study was approved by the ethics committee of the Anna Meyer Children’s University Hospital in Florence, Italy. Statistical analysis The study population was characterised on the basis of age, gender, nationality, the season when the child was hospitalised, the presence of complications, hospital admitting, median length of stay and mode of discharge. Patients were stratified by four age groups: 0–11 months, 12 months to 4 years, 5–9 years and 10–17 years. Rates of hospitalisation for pertussis were calculated as cases per 100 000 children living in Tuscany, and the 95% confidence intervals (CI) were calculated using an exact binomial distribution. Categorical variables were analysed using the v2 or the v2 for trend tests (Cochran–Armitage test for trend). All significant tests were two sided. We considered a value of p < 0.05 significant. The statistical analyses were performed using the SPSS software package (SPSS 11.5; Chicago, IL, USA).
RESULTS During the study period, 279 children were hospitalised for pertussis by the 31 Tuscan hospitals in the region, and the characteristics of the study population are summarised in Table S1. Median age was 3 months, and the interquartile range (IQR) was 1–11. More than three-quarters (75.63%) of the 279 hospitalisations occurred in the zero- to 11month age group, and 62% of the subjects studied were children in their first 3 months of life, who had not yet started the immunisation schedule. The infant group also presented with the highest rate of pertussis-related complications (51 of 211, 24.17%) of any age group, as reported in Figure 1. Pneumonia was the main complication in this age
Figure 1 Pertussis: cases and complications by age group in Tuscan children from 2000 to 2012.
group (32 of 211), followed by respiratory failure (11 of 211), acute bronchiolitis (6 of 211), sepsis (1 of 211) and syncope (1 of 211). Two of 279 children died during hospitalisation, providing a crude mortality rate of 7.17 per 1000 children (95% CI: 4.14–101.95) and a case fatality rate of 9.47 per 1000 infants (95% CI: 5.56–134.31). Both children were female and aged
