Pertussis Hospitalizations Research Articles

Pertussis in infancy and the association with respiratory and cognitive disorders at toddler age

Pertussis in unvaccinated infants can run a severe course and is often accompanied by complications. In this pilot study, we studied whether there is an association between pertussis hospitalisation in infancy and, respiratory symptoms, growth and cognitive development in early childhood. A group of 89 children aged 13-45 months and hospitalised for laboratory confirmed pertussis within the first six months of their life were compared with 172 children without a history of pertussis. Risk ratios (RR) with 95% confidence intervals (CI) of the association between health outcomes and pertussis in infancy were calculated. Weight-for-length and length-for-age z-scores were calculated to investigate growth. Van Wiechen scores were compared to study cognitive development. Children with a history of pertussis in infancy had a greater chance on "asthma symptoms" (RR 2.8 95%CI 1.1-7.0) on toddler age and were more likely to report "respiratory infections" (RR 3.3 95%CI 1.6-6.6). In addition, children with a history of pertussis in infancy had significantly lower weight-for-height in the first 40 months of life. No significant differences in cognitive development were found. We found an association between severe pertussis in infancy and respiratory symptoms on toddler age. The mechanisms that may underlie this association require further investigation.

Pertussis after end of a mass vaccination project—End of the “vaccination honey-moon”

After 16 years of no vaccination against pertussis in Sweden, mass vaccination of infants and catch-up vaccination of children up to 10 years with a monocomponent pertussis toxoid vaccine was performed in the Greater Gothenburg area of Sweden between 1995 and 1999. At the end of the project in February 1999, 56% of all 10 year old children born in the Greater Gothenburg area had received 3 doses of the pertussis toxoid. No booster doses were given. This led to a temporary almost complete elimination of the disease. The aim of the present study was to follow the incidence of pertussis after end of the mass vaccination project (1999–2009) as it is reflected by laboratory verified cases (cultures and/or PCR) and pertussis hospitalizations. A reemergence of pertussis was seen from the end of 1999 with a peak in 2004 followed by a decrease when booster doses to both 6 and 10 year old children were introduced in 2005–2006. From July 1, 1999 through December 31, 2009 a total of 1973 cases were diagnosed with culture or PCR. The disease was prevalent in all age groups. The highest documented incidence was seen in infants younger than 12 months. 450 patients with verified pertussis had received 3 doses of the pertussis toxoid vaccine in the mass vaccination project and some other trials (comprising a total of 69,423 children). The mean time from the last dose to the laboratory verification of pertussis was 5 years in these 450 cases. There were 128 hospitalizations, 106 of which were in infants. In conclusion, pertussis is still not eliminated from the area. Booster doses are needed but the numbers and optimal timing are not known.

Review of the 2008–2009 pertussis epidemic in NSW: notifications and hospitalisations

In 2008 and 2009 increased numbers of pertussis notifications were reported in NSW. During the epidemic period, the pertussis notification rate was 2.7 times higher than the previous 5-year average. Rates of pertussis notifications and hospitalisations were highest among infants aged less than 1 year across all years studied. Compared to previous years, the notification rate for children aged 1-4 years increased dramatically and was particularly striking for children aged 3 years with notifications exceeding those for infants in 2009. Changes in testing practices during the epidemic period, including a significant increase in the use of polymerase chain reaction, may account for some of the relative increase in size of the 2008-2009 outbreak compared with previous outbreak years.

Effectiveness of two pertussis vaccines in preterm Danish children

Reduced immunogenicity in preterm children has been observed for pertussis vaccines. How immunogenicity relates to clinical protection is not well-established for pertussis, and the corresponding reduction, if any, in post-licensure vaccination effectiveness among preterm children has not been determined. We conducted a nationwide cohort study of 879,424 Danish children including 1553 cases of pertussis hospitalisation. The effectiveness of pertussis vaccination, both whole-cell and acellular, was evaluated in preterm and full-term children. The effectiveness of a completed primary series of pertussis vaccination, whole-cell or acellular, was similar in preterm and full-term children.

The epidemiology of pertussis in Germany: past and present

BackgroundCurrent and past pertussis epidemiology in the two parts of Germany is compared in the context of different histories of vaccination recommendations and coverage to better understand patterns of disease transmission.MethodsAvailable regional pertussis surveillance and vaccination coverage data, supplemented by a literature search for published surveys as well as official national hospital and mortality statistics, were analyzed in the context of respective vaccination recommendations from 1964 onwards.ResultsRoutine childhood pertussis vaccination was recommended in the German Democratic Republic (GDR) from 1964 and in former West German states (FWG) from 1969, but withdrawn from 1974–1991 in FWG. Pertussis incidence declined to <1 case/100.000 inhabitants in GDR prior to reunification in 1991, while in FWG, where pertussis was not notifiable after 1961, incidence was estimated at 160–180 cases/100.000 inhabitants in the 1970s-1980s. Despite recommendations for universal childhood immunization in 1991, vaccination coverage decreased in former East German States (FEG) and increased only slowly in FWG. After introduction of acellular pertussis vaccines in 1995, vaccination coverage increased markedly among younger children, but remains low in adolescents, especially in FWG, despite introduction of a booster vaccination for 9–17 year olds in 2000. Reported pertussis incidence increased in FEG to 39.3 cases/100.000 inhabitants in 2007, with the proportion of adults increasing from 20% in 1995 to 68% in 2007. From 2004–2007, incidence was highest among 5–14 year-old children, with a high proportion fully vaccinated according to official recommendations, which did not include a preschool booster until 2006. Hospital discharge statistics revealed a ~2-fold higher pertussis morbidity among infants in FWG than FEG.ConclusionThe shift in pertussis morbidity to older age groups observed in FEG is similar to reports from other countries with longstanding vaccination programs and suggests that additional booster vaccination may be necessary beyond adolescence. The high proportion of fully vaccinated cases in older children in FEG suggests waning immunity 5–10 years after primary immunisation in infancy. The higher incidence of pertussis hospitalisations in infants suggests a stronger force of infection in FWG than FEG. Nationwide pertussis reporting is required for better evaluation of transmission patterns and vaccination policy in both parts of Germany.

Potential Impact of Acceleration of the Pertussis Vaccine Primary Series for Infants

This study estimates the potential impact, on rates of pertussis infections, hospitalizations, and deaths among infants in the United States, of administering the first dose of diphtheria and tetanus toxoids and acellular pertussis vaccine at 6 weeks rather than 2 months of age. We used existing data to estimate current US rates of pertussis infections, hospitalizations, and deaths according to age and infant population in 2004. We then estimated the potential impact of accelerating the administration of the first dose of diphtheria and tetanus toxoids and acellular pertussis vaccine from 2 months to 6 weeks of age, an alternative schedule consistent with current vaccination guidelines. We used Poisson distribution analysis to determine 95% confidence intervals for projected rates of pertussis disease. Acceleration of administration of the first dose of diphtheria and tetanus toxoids and acellular pertussis vaccine from 2 months to 6 weeks of age is expected to prevent 1236 cases of pertussis, 898 hospitalizations, and 7 deaths attributable to pertussis per year in the United States. These decreases represent 9% reduction in cases, 9% reduction in hospitalizations, and 6% reduction in deaths attributable to pertussis among infants <3 months of age. Acceleration of the second and third doses by 2 weeks is expected to prevent an additional 923 cases, 520 hospitalizations, and 2 deaths attributable to pertussis each year. Acceleration of administration of diphtheria and tetanus toxoids and acellular pertussis vaccine from 2 months to 6 weeks should reduce the burden of pertussis among young infants.

Pertussis among American Indian and Alaska Native infants

Collaborators from the Centers for Disease Control and Prevention and other public health programs report the substantially increased burden of hospitalization for pertussis among American Indian and Alaska Native (AI/AN) infants compared with the general U.S. infant population. Cases occur primarily in infants too young to be afforded protection from the current pertussis immunization schedule that begins at two months of age and despite vaccination coverage rates similar to or just slightly lower than national coverage levels. Additional strategies will be required to reduce the burden. Because the Alaska and Southwest regions, among seven regions, account for the majority of the differences between AI/AN children and the general U.S. population, it is likely that ethnicity per se is one contributing factor among others such as geography, environment, and social factors. Collaborators from the Centers for Disease Control and Prevention and other public health programs report the substantially increased burden of hospitalization for pertussis among American Indian and Alaska Native (AI/AN) infants compared with the general U.S. infant population. Cases occur primarily in infants too young to be afforded protection from the current pertussis immunization schedule that begins at two months of age and despite vaccination coverage rates similar to or just slightly lower than national coverage levels. Additional strategies will be required to reduce the burden. Because the Alaska and Southwest regions, among seven regions, account for the majority of the differences between AI/AN children and the general U.S. population, it is likely that ethnicity per se is one contributing factor among others such as geography, environment, and social factors.

Epidemiología de las hospitalizaciones atribuibles a infección por Bordetella pertussis en población general en España (1999-2005)

ObjectiveBordetella pertussis infection has high hospitalization and morbidity rates in spite of the high vaccine coverage.The aim of this study was to estimate the rate of hospitalization due to B. pertussis infection in Spain, from 1999 to 2005. Material and methodsA retrospective study was carried out using the National Epidemiologic Surveillance System for hospital data (Minimum Basic Data Set [MBDS]) to obtain information on hospitalization, age, length of hospitalization, mortality, case-fatality rates and associated costs. ResultsDuring the study period, 3727 pertussis hospitalizations were recorded (Spanish Version of the International Classification of Diseases, 9th Revision, Clinical Modification: ICD-9-CM codes 033 y 484.3, any diagnostic position), a global annual hospitalization rate of 1.34 per 100,000 people. 85.6% of hospitalizations occurred in children up to 1 year of age, and 95% in children younger than 5 years of age. The highest hospitalization rate was registered in Ceuta and Melilla. The average length of hospitalization was 8.8±8.3 days. During the 7-year study period, there were 23 deaths, of which 16 (69.6%) occurred in children below 1 year of age. The case-fatality rate was 0.62%. The total mean annual cost to the National Health System was 1,024,794.41 €. ConclusionsThe epidemiological pattern found suggests that there are population groups not protected against pertussis,which results in morbidity, mortality and a substantial use of healthcare resources. Booster doses of the vaccine should be given to protect teenagers and adults, which will indirectly protect susceptible, breast-feeding babies.

Pertussis Hospitalizations Among Infants in the United States, 1993 to 2004

We sought to describe the rates of pertussis hospitalization among infants by using databases that do not rely on passive reporting and compare with results obtained from the passive national surveillance system. The incidence of infant pertussis hospitalization in 1993 to 2004 was determined by using 2 national hospitalization discharge databases (Nationwide Inpatient Sample and Kids' Inpatient Database) and the National Notifiable Disease Surveillance System/Supplemental Pertussis Surveillance System. Rates were determined for separate age groups among infants < 1 year of age. Pertussis complications and procedures were examined by using the Kids' Inpatient Database. In 1993 to 2004, the pertussis hospitalization rates for infants < or = 2 months of age were generally stable, by the discharge databases. The incidence of infant pertussis hospitalization obtained from the Nationwide Inpatient Sample and Kids' Inpatient Database was approximately 2 times greater than that obtained from the passive reporting system. Infants 1 to 2 months of age had the highest incidence (239 hospitalizations per 100,000 live births in the 2003 Kids' Inpatient Database). An annual average of 2678 hospitalizations occurred in 2000 and 2003; 86% occurred in infants < or = 3 months of age. Among those with ages provided, 95% of infants who required mechanical ventilation and all of those who died were < or = 3 months of age. Pertussis hospitalization incidence rates among the youngest infants were generally stable in 1993 to 2004 and were highest for infants 1 to 2 months of age. The impact of the new adolescent and adult tetanus-diphtheria-acellular pertussis vaccines on infant pertussis should be monitored through such discharge databases. Additional vaccination strategies should be evaluated to protect infants as early in life as possible.

Pertussis-Associated Hospitalizations in American Indian and Alaska Native Infants

To investigate the burden of pertussis in American Indian and Alaska Native (AI/AN) infants. AI/AN pertussis-associated hospitalizations between 1980 and 2004 were evaluated using Indian Health Service (IHS)/tribal inpatient data, which include all reported hospitalizations within the IHS/tribal health care system. Between 1980 and 2004, 483 pertussis-associated hospitalizations in AI/AN infants were documented; 88% of cases involved infants age < 6 months. For this entire period, the average annual hospitalization rate was 132.7 per 100,000 AI/AN infants (95% confidence interval [CI] = 121.3 to 145.2), and 234.5 per 100,000 AI/AN infants age < 6 months (95% CI = 213.1 to 258.1). Between 2000 and 2004, the annual hospitalization rate was 100.5 per 100,000 AI/AN infants (95% CI = 81.6 to 123.7), which exceeds the estimated 2003 pertussis hospitalization rate of 67.7 per 100,000 in the general US infant population (95% CI = 61.9 to 73.5). The highest pertussis hospitalization rates in 2000 to 2004 were in AI/AN infants in the Alaska and Southwestern IHS regions of the United States. The burden of pertussis in AI/AN infants is high, particularly so in infants age < 6 months in the Alaska and the Southwestern IHS regions of the United States. Ensuring implementation of vaccination strategies to reduce the incidence of pertussis in AI/AN, infants, adolescents, and adults alike is warranted to reduce the burden of pertussis in AI/AN infants.

Infants hospitalised with pertussis: Estimating the true disease burden

New Zealand (NZ) has a large pertussis disease burden compared with other developed countries. Accurate ascertainment of disease burden is fundamental to controlling pertussis and informing immunisation policy. Disease burden estimates are primarily from passive surveillance, which underestimates disease incidence. The aim of this study is to use active surveillance to determine pertussis disease burden in infants hospitalised in NZ. Using the NZ Paediatric Surveillance Unit, active surveillance from 08/2004 to 07/2005 for infants <12 months old, hospitalised with pertussis. 110 infants identified (196 per 100,000), including six with complications, eight intensive care admissions and one death. The hospitalisation rate (per 100,000) varied with ethnicity, being higher for Maori (296) and Pacific (358) compared with European/other (117). Twenty-four per cent were too young to be immunised. Of infants 6 weeks and older 46% had received no immunisations. Despite being more likely to be immunised Pacific infants had a higher hospitalisation rate owing to a larger proportion acquiring pertussis prior to age 6 weeks. Cyanosis and apnoea were frequent symptoms in young infants. Under-identification, estimated using capture-recapture analysis, was modest for both active surveillance (16%) and passive notification (19%). Infant pertussis hospitalisation rates are three to six times greater than rates in the USA, England and Australia. Underestimation of disease burden by passive notification in hospitalised infants is modest, suggesting a high degree of clinical awareness by paediatricians in NZ. New immunisation strategies are needed to protect infants from a younger age.

Hospitalisations due to pertussis in New Zealand in the pre‐immunisation and mass immunisation eras

Pertussis disease burden in New Zealand in recent decades has been large compared with other developed countries. However, these comparisons use data from relatively short time periods given the long epidemic cycle of pertussis. To better understand the current disease burden, this study examined pertussis hospitalisation data in New Zealand in both the pre-immunisation and mass immunisation eras. Hospital discharge data and population data from 1873 to 2004 were used to estimate average pertussis hospital discharge rates per decade. Rates were compared using relative risks and 95% confidence intervals (CI). Average annual pertussis hospitalisation rates per 100000 were less than two from 1873 to 1919, increased to 12 in the 1940s, decreased to less than four in the 1960s and have increased since then with the rate in the current decade being 5.8. Compared with the 1960s (3.8 per 100000) the average annual rate has been significantly greater in the 1980s (RR=1.11, 95% CI 1.03, 1.21), 1990 s (RR=1.33, 95% CI 1.23, 1.44) and 2000s (RR=1.55, 95% CI 1.42, 1.68). Since 1960 hospitalisation rates have increased for those less than one year old, one to four years old and five years and older. The increases have been most marked for infants (RR 2000s vs. 1960s=2.87, 95% CI 2.59, 3.18). After an initial decline following mass immunisation, pertussis hospitalisation rates in New Zealand have subsequently increased steadily. To reduce pertussis disease burden improved immunisation coverage and timeliness is required and consideration given to spreading the pertussis vaccine schedule over a wider age range.

The Effect of Changing From Whole-Cell to Acellular Pertussis Vaccine on the Epidemiology of Hospitalized Children With Pertussis in Canada

Between July 1997 and April 1998, universal childhood immunization programs in Canada changed from using a whole-cell pertussis to a 5-component acellular pertussis-containing vaccine. To assess effects on pertussis epidemiology of this nationwide change, we analyzed hospitalizations during 1991-2004 using the Canadian Immunization Monitoring Program, Active (IMPACT) pertussis database. IMPACT is an active surveillance network based in 12 pediatric tertiary-care hospitals across Canada. Characteristics of hospitalized cases of pertussis were compared by type of vaccine received or by birth date (if immunization records were unavailable or the child was unvaccinated). Age-stratified incidence rates were calculated by year and vaccine type. Two thousand ninety-six cases of pertussis were admitted to IMPACT centers, 1174 during the whole-cell vaccine program (WCV-P) and 842 during the acellular vaccine program (ACV-P). Pertussis incidence among children <5 years old decreased significantly during the ACV-P, causing an increase in the residual proportion of cases either too young to be immunized (<2 months old: ACV-P 39% versus WCV-P 26.1%; P < 0.0001) or too young for a second dose (2-3 months old: 42.9% versus 34.2%, respectively; P < 0.0001). A significantly smaller proportion of cases (ACV-P 15.1% versus WCV-P 27.3%) occurred in infants who were old enough (4-11 months of age) to have received 2 or 3 doses of vaccine. With ACV-P, pertussis hospitalizations in children 4-59 months old decreased in frequency, consistent with improved vaccine effectiveness, but remained prominent among very young infants. Improved control strategies are needed to reduce infections among infants too young for pertussis vaccination.

Higher pertussis hospitalization rates in indigenous Australian infants, and delayed vaccination

This ecological study aimed to identify possible reasons for higher pertussis hospitalization rates in indigenous Australian infants. Two national datasets were analysed: the Hospital Morbidity Database and the Australian Childhood Immunisation Register (ACIR). Most (52%) pertussis hospitalizations in indigenous infants occurred at 0–2 months of age, and rates in these indigenous infants were significantly higher in remote areas. Indigenous infants had higher hospitalization rates and more frequently delayed vaccination than non-indigenous infants of the same age. These data suggest that residence in a remote area, as a proxy for poorer living conditions for indigenous people, and delayed vaccination, both contribute to higher pertussis hospitalization rates in indigenous infants.

The impact of pre-school booster vaccination of 4–6-year-old children on pertussis in 0–1-year-old children

Pertussis in young children is severe and relatively prevalent in vaccinated populations. We estimated the impact of pre-school booster vaccination of 4–6-year-old children on pertussis in 0–1-year-old children. We conducted a population-based historical cohort study of all children born in Denmark, 1977–2001 ( N = 1,536,717) using information on place of residence to identify household members and vaccination history from nationwide registers. We estimated rate ratios (RRs) of pertussis hospitalisation among children in the cohort according to number, age, and vaccination status of their household members. This enabled, through population attributable risks, the estimation of the preventable proportion of hospitalisations among 0–1-year-old children according to age at booster vaccination (4–6 years), booster uptake, and the efficacy of the booster against transmission. The preventable proportion of pertussis hospitalisations among 0–1-year-old children ranged from 7% to 33% (most realistic scenario = 18%), varying according to age at booster vaccination, uptake, and efficacy of booster against transmission. This relatively limited impact of a pre-school booster was partly a consequence of the actual number of 0–1-year-old children living with children of pre-school age or older and partly the result of significant exposure from children younger than pre-school age in the household. According to our model the effectiveness of pre-school booster vaccination as an intervention to prevent pertussis hospitalisation of 0–1-year-old children is modest.

Hospitalization for pertussis: profiles and case costs by age.

BackgroundPertussis, a highly contagious respiratory illness, affects people of all ages and can have serious clinical consequences. It has been reported that from 1997–2000, 20% of all pertussis cases required hospitalization in the US. This analysis examined demographics, case fatality rate, resource use and costs of hospital care related to pertussis by age.MethodsICD-9 codes (033.0, 033.9) were used to identify cases of pertussis in hospital discharge databases from roughly 1,000 US hospitals in 4 states (California, Florida, Maryland, Massachusetts). Data from 1996–1999 were examined by age group. Separate analyses were done for infants (<1 year) and children (1–11 years); however, adolescent and adult cases were combined into one group (12+ years), due to the small number of cases. Databases were used to determine demographics, health service utilization and care costs. Cost estimates include accommodations, ancillary and physician services, reported in 2002 US$.ResultsOf the 2,518 cases identified, 90% were infants. The inpatient case fatality rate was <1%. Of survivors, 99% were discharged home (6% with home health care); 1% required further sub-acute inpatient care. For the 2,266 infants, the mean LOS was 6 days at a cost of $9,586 per stay. Children (n = 191) had a mean LOS of 3.7 and cost of $4,729; adolescents/adults (n = 61, mean age 40 years) stayed on average 3.4 days with a cost of $5,683 per hospitalization.ConclusionInfants are responsible for the bulk of hospitalizations and generate higher inpatient costs. Costly hospital care occurs, however, in patients with pertussis at all ages.

Epidemiology and Surveillance of Pertussis Among Infants in Catalonia, Spain, During 1997–2001

Despite high levels of vaccination coverage in Spain and Catalonia (98% in 2002), pertussis is a significant cause of morbidity among infants. The study aim was to estimate the incidence of hospitalizations for pertussis among infants from 1997 through 2001 in Catalonia. A retrospective review of records for patients <12 months of age with a diagnosis of pertussis (International Classification of Diseases, 9th revision, code 033) at discharge from 11 Catalonian hospitals was performed. Three hundred forty-six patients were identified, 62 (1997), 28 (1998), 59 (1999), 150 (2000) and 47 (2001), of whom 284 (82%) were <4 months of age. The incidence of hospitalizations because of whooping cough from 1997 through 2001 in Catalonia was estimated at 118 cases per 100,000 inhabitants <12 months of age. Symptoms included paroxysmal cough (95%), cyanosis (67.9%), vomiting (36.7%) and apneic episodes (27.7%). Three infants (0.8%) died, all <2 months of age. Two hundred thirty-four patients (67.6%) were unvaccinated (222 patients were <3 months of age). Six patients (1.7%) were fully vaccinated (3 doses). Considering that only 220 patients <12 months of age were reported through the Catalonian Notification System in 1997-2001, at least 126 hospitalizations (36.4%) for pertussis were not reported to this system (mean difference per year, 32.6%; range, 8.4-56%). In this study, hospitalizations exceeded the number of notifications by at least 32.6%; therefore, the real incidence is likely to be greatly underestimated. Pertussis incidence remains high among infants, most of whom are <4 months of age and have had no or 1 dose of vaccine.

National study of infants hospitalized with pertussis in the acellular vaccine era.

In Australia in 1999 acellular pertussis vaccine (DTPa) replaced locally manufactured whole cell vaccine given at 2, 4 and 6 months of age with coverage of about 95% by 12 months of age. Few data are available on pertussis hospitalizations or sources of infection in countries exclusively using DTPa. In 2001 national active monthly surveillance of infant hospitalizations for pertussis was conducted through the Australian Pediatric Surveillance Unit, which surveys all child health specialists monthly. A standard questionnaire was completed for notified cases. There were 140 infants reported (median age at diagnosis, 8 weeks). The rate of hospitalization in indigenous infants was significantly higher than in nonindigenous infants (P < 0.01). Of 97 (69%) infants who had not been vaccinated for pertussis, 63 (65%) were <8 weeks old (before the first scheduled dose of DTPa vaccine). Of 76 infants age > or =8 weeks, only 28 (37%) were appropriately immunized for age. Of 68 coughing contacts whose ages were known, 46 (68%) were adults, usually one of the infant's parents. Of 32 child contacts 16 (50%) were siblings. Four infants <6 weeks old died. Despite universal vaccination with DTPa in Australia, pertussis remains an important cause of hospitalization, morbidity and death in infants, most of whom were too young to be vaccinated or had missed vaccinations. The most common source of infection was a parent. Strategies to improve pertussis control in countries with high DTPa coverage could include adult-formulated booster pertussis vaccines for adolescents and recent parents and/or accelerated pertussis vaccine schedules for infants.

Use of Birth Certificates and Surveillance Data to Characterize Reported Pertussis among Texas Infants and Young Children, 1995 to 2000

Pertussis morbidity is increasing, especially among young infants and children, who are more likely to be hospitalized and have more severe complications. Maternal and pediatric factors associated with underimmunization and hospitalization for pertussis are poorly understood, but young maternal age and low birth weight have been associated with pertussis among young infants. We used pertussis surveillance data, matching cases to the birth certificates of 416 Texas infants and children reported as pertussis cases during 1995 to 2000. Maternal/pediatric information gathered from birth certificates included birth weight, gestational age, and maternal factors (age, birthplace and education level, prenatal care, and previous live births). We assessed the immunization status of the cases and maternal/pediatric factors associated with underimmunization with a pertussis-containing vaccine and hospitalization using descriptive statistics and logistic regression. The 416 cases represented 20% of the pertussis morbidity in Texas from 1995 through 2000. Most children had not been vaccinated (275 [66%]), even though 374 (90%) were old enough for at least one dose. Among those 374 children, only those younger than 6 months were associated with underimmunization (odds ratio [OR], 9.98; 95% confidence interval [CI], 6.24-15.97). Most patients (253 [61%]) were hospitalized. Hospitalization was associated with complications of apnea (OR, 2.13; 95% CI, 1.39 2.38), pneumonia (OR, 5.26; 95% CI, 2.94-11.59), and age younger than 6 months (OR, 2.11; 95% CI, 1.38-3.23). More than two-thirds of the children reported as pertussis cases were old enough to have at least one dose of a pertussis-containing vaccine but were not immunized. Maternal and pediatric characteristics on birth certificates were not useful in predicting either underimmunization or hospitalization for pertussis complications. More current assessments of maternal and pediatric characteristics should be part of pertussis contact investigations.

Hospital admissions for pertussis in Spain, 1995–1998

This epidemiological survey was undertaken to estimate the annual burden of hospitalizations for pertussis in Spain during a four-year period 1995–1998. Data were obtained from the national surveillance system for hospital data. All hospital discharges for pertussis (ICD-9- CM 033) were analyzed. The annual incidence of hospitalization for pertussis was 1.7 per 100,000 population. Eighty-nine percent of the cases were <1 year of age (incidence of 78 per 100,000) and 95% were ≤5 years of age (incidence of 28 per 100,000). During the study period, 14 deaths were reported among patients hospitalized by pertussis. Despite of the high inmunization rates, many pertussis cases occur each year, mostly of them among very young children.