Maternal Vaccination in Argentina: Tetanus, Diphtheria, and Acellular Pertussis Vaccine Effectiveness During Pregnancy in Preventing Pertussis in Infants <2 Months of Age

BACKGROUND

In 2011, Argentina experienced its highest pertussis incidence and mortality rates of the last decade; 60% of deaths were among infants aged <2 months. In response, a dose of tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis (Tdap) vaccine was recommended for all pregnant women at ≥20 weeks of gestation. Although recent studies suggest that maternal Tdap vaccination is effective at preventing infant disease, no data have come from low- or middle-income countries, nor from ones using whole-cell pertussis vaccines for primary immunization.

METHODS

We conducted a matched case-control evaluation to assess the effectiveness of maternal Tdap vaccination in preventing pertussis among infants aged <2 months in Argentina. Pertussis case patients identified from September 2012 to March 2016 at 6 hospital sites and confirmed by polymerase chain reaction testing were included. Five randomly selected controls were matched to each case patient by hospital site and mother's health district. We used multivariable conditional logistic regression to calculate odds ratios (ORs). Vaccine effectiveness (VE) was estimated as (1 - OR) × 100%.

RESULTS

Seventy-one case patients and 300 controls were included in the analysis. Forty-nine percent of case patients and 78% of controls had mothers who were vaccinated during pregnancy. Overall Tdap VE was estimated at 80.7% (95% confidence interval, 52.1%-92.2%). We found similar VE whether Tdap was administered during the second or third trimester.

CONCLUSIONS

Tdap vaccination during pregnancy is effective in preventing pertussis in infants aged <2 months in Argentina, with similar effectiveness whether administered during the second or third trimester of pregnancy.

Haemophilus influenzae type B meningitis: Is there a re-emergence? 24 years of experience in a children's hospital

INTRODUCTION

Haemophilus influenzae type B (Hib) used to be the main cause of bacterial meningitis in children younger than 5 years old. Following the introduction of the Hib vaccine in the immunization schedule (1998), its incidence reduced significantly but it has increased over the last years. The objectives of this study included describing the characteristics and analyzing the epidemic curve of Haemophilus influenzae type B (Hib) meningitis by comparing the pre- and postimmunization periods.

MATERIALS AND METHODS

Time-series study. All patients hospitalized with Hib meningitis at Hospital de Niños "R. Gutiérrez" (January 1992-May 2016). Hospitalization rates were compared before (pre-immunization) and after (post-immunization) the introduction of the Hib vaccine. The post-immunization period was divided into three similar periods.

RESULTS

Eighty-five patients with Hib meningitis were admitted (73.3% in the pre-immunization period). No differences were observed in relation to the clinical and sociodemographic characteristics of cases in both periods. Pre-immunization: 10.5 cases/year; postimmunization: 0.7 cases/year. As of 2014, the rate has increased. Lethality rate: 4.8% (all preimmunization). Post-immunization data (n= 15): 40% had completed their primary immunization schedule, 40% were delayed on the immunization schedule for their age. Overall reduction in the hospital rate of Hib meningitis by 89.8% (95% confidence interval: -82.79-93.96%, p < 0.001) in the post-immunization period. The analysis of the different post-immunization periods shows a decline in reduction over time.

CONCLUSIONS

A very significant reduction in hospitalizations due to Hib meningitis was observed after the Hib vaccine was introduced; however, over the past years, the number of cases has increased although no changes have been observed in patient characteristics.

Influenza virus: 16 years' experience of clinical epidemiologic patterns and associated infection factors in hospitalized children in Argentina

Background

Influenza is an important cause of acute lower respiratory tract infection (aLRTI), hospitalization, and mortality in children. This study aimed to describe the clinical and epidemiologic patterns and infection factors associated with influenza, and compare case features of influenza A and B.

Methods

In a prospective, cross-sectional study, patients admitted for aLRTI, between 2000 and 2015, were tested for respiratory syncytial virus, adenovirus, influenza, or parainfluenza, and confirmed by fluorescent antibody (FA) or real-time polymerase chain reaction (RT-PCR) assay of nasopharyngeal aspirates.

Results

Of 14,044 patients, 37.7% (5290) had FA- or RT-PCR-confirmed samples that identified influenza in 2.8% (394/14,044; 91.4% [360] influenza A, 8.6% [34] influenza B) of cases. Influenza frequency followed a seasonal epidemic pattern (May–July, the lowest average temperature months). The median age of cases was 12 months (interquartile range: 6–21 months); 56.1% (221/394) of cases were male. Consolidated pneumonia was the most frequent clinical presentation (56.9%; 224/394). Roughly half (49.7%; 196/394) of all cases had previous respiratory admissions; 9.4% (37/394) were re-admissions; 61.5% (241/392) had comorbidities; 26.2% (102/389) had complications; 7.8% (30/384) had nosocomial infections. The average case fatality rate was 2.1% (8/389). Chronic neurologic disease was significantly higher in influenza B cases compared to influenza A cases (p = 0.030). The independent predictors for influenza were: age ≥6 months, odds ratio (OR): 1.88 (95% confidence interval [CI]: 1.44–2.45); p<0.001; presence of chronic neurologic disease, OR: 1.48 (95% CI: 1.01–2.17); p = 0.041; previous respiratory admissions, OR: 1.71 (95% CI: 1.36–2.14); p<0.001; re-admissions, OR: 1.71 (95% CI: 1.17–2.51); p = 0.006; clinical pneumonia, OR: 1.50 (95% CI: 1.21–1.87); p<0.001; immunodeficiency, OR: 1.87 (95% CI: 1.15–3.05); p = 0.011; cystic fibrosis, OR: 4.42 (95% CI: 1.29–15.14); p = 0.018.

Conclusion

Influenza showed an epidemic seasonal pattern (May–July), with higher risk in children ≥6 months, or with pneumonia, previous respiratory admissions, or certain comorbidities.

Impact of a maternal immunization program against pertussis in a developing country

BACKGROUND

Pertussis disease is a growing concern for developing countries. In Argentina, rates of illness and death peaked in 2011. More than 50% of fatalities due to pertussis occurred in infants younger than two months of age, too young for vaccination. In 2012, the government offered immunization with a vaccine containing Tdap to all pregnant women after 20weeks of gestation with the intent of reducing morbidity and mortality in young infants.

METHODS

Maternal acellular pertussis vaccine impact on reducing infant disease burden was estimated based on data from the Argentinean Health Surveillance System. We divided Argentinean states in two groups experiencing high (>50) and low (⩽50) Tdap vaccine coverage and compared these two groups using a Bayesian structural time-series model. Low coverage regions were used as a control group, and the time series were compared before and after the implementation of the Tdap program.

FINDINGS

We observed a relative reduction of 51% (95% CI [-67%, -35%]; p=0.001) in pertussis cases in high coverage states in comparison with the low coverage areas. Analysis of infants between two and six months showed a 44% (95% CI [-66%, -24%]; p=0.001) reduction in illness. Number of deaths was highest in 2011 with 76 fatalities, for an incidence rate of 2.9 per 100,000. Comparing with 2011, rates decreased by 87% to 10 subjects, or 0.9 per 100,000 in 2013.

INTERPRETATION

We show an age-dependent protective effect of maternal Tdap immunization in a developing country for infants younger than six months.

Epidemiological situation of pertussis and strategies to control it: Argentina, 2002-2011

INTRODUCTION

Pertussis is a challenge for public health.

OBJECTIVES

To describe pertussis-related morbidity and mortality and immunization coverage for the 2002-2011 period, profile of cases for 2011, and control strategies implemented by the Ministry of Health (MoH) of Argentina.

METHODS

Descriptive, epidemiological surveillance study. Morbidity data were obtained from the National Health Surveillance System, while mortality data were obtained from the MoH's Health Statistics and Information Department and official jurisdictional reports. Administrative immunization coverage was used based on the data provided by the MoH's jurisdictions. The Epi Info software, version 7.1.2, was used for analysis.

RESULTS

The number of reported cases of pertussis increased between 2002 and 2011, reaching its peak in 2011: an incidence of 16 x 100 000 inhabitants, and 76 deaths. Most deaths occurred in infants younger than 1 year old. Immunization coverage achieved at a national level with the third dose and the dose administered at the time of starting primary education was >90%, while the coverage achieved with the first booster dose was 80%-90%. In 2011, 2821 confirmed cases were reported (incidence of 7 x 100 000 inhabitants): 84% in infants <1 year old; 76 deaths: 97% in infants <1 year old (60.5% in infants <2 months old). Among the strategies that were deployed, a total of 906 clinical nodes and 405 laboratory nodes were consolidated; the use of the polymerase chain reaction as a diagnostic method and the differential classification of cases were implemented, and additional vaccine doses were administered.

CONCLUSIONS

The number of pertussis cases increased between 2002 and 2011; the highest morbidity and mortality occurred in infants younger than 1 year old; immunization coverage reached 80%-90%. . The highest number of pertussis-related deaths was recorded in 2011. The MoH strengthened the epidemiological surveillance and set guidelines for control measures.

Cost of Bordetella pertussis illness in tertiary hospitals in Argentina

The National Immunization Commission and the National Program for the Control of Vaccine-Preventable Diseases (Programa Nacional de Control de Enfermedades Inmunoprevenibles, ProNaCEI) updated the immunization policy in relation to Bordetella pertussis (BP) in 2009 in order to improve the control of this disease in accordance with international recommendations. To evaluate the financial impact of this new immunization policy, we must first know the cost on the health system of having a hospitalized or outpatient child infected with BP. The objective of this study was to describe the profile of costs of hospitalized or outpatient children with laboratory-confirmed BP infection in three hospitals of Argentina. This was a prospective study of the cost of BP in the period between December 2010 and March 2012.

RESULTS

The total cost for the entire cohort was 1,170,663.32 ARS (236,497.64 USD); direct medical costs were 1,124,052.31 ARS (227,081.27 USD); indirect costs and out-of-pocket expenses were 46,611 ARS (9416.6 USD). From this data, it is possible to conclude that the total average cost per patient was 10 546.52 ARS (95% CI: 9009-13,840) (2130.60 USD, 95% CI: 1820-2795), the direct medical cost per patient was 10 126.6 ARS (95% CI: 8607-13,171) (2045.77 USD, 95% CI: 1738-2660), and the indirect plus out-of-pocket costs (transportation and extras) were 419.92 ARS (95% CI: 344.7-565.3) (84 USD, 95% CI: 69-115).

CONCLUSION

The cost of a hospitalized child with confirmed BP is 10,546.52 ARS (95% CI: 9009-13,840) (2130.60 USD, 95% CI: 1820-2795). Direct non-medical costs and overhead costs account for 4% of the total cost, amounting to 419.91 ARS per family (84 USD, 95% CI: 69-115), approximately an 8% of an average salary.

Impact of vaccination against Haemophilus influenzae type b with and without a booster dose on meningitis in four South American countries

To inform World Health Organization recommendations regarding use of Haemophilus influenzae type b (Hib) vaccines in national immunization programs, a multi-country evaluation of trends in Hib meningitis incidence and prevalence of nasopharyngeal Hib carriage was conducted in four South American countries using either a primary, three-dose immunization schedule without a booster dose or with a booster dose in the second year of life. Surveillance data suggest that high coverage of Hib conjugate vaccine sustained low incidence of Hib meningitis and low prevalence of Hib carriage whether or not a booster dose was used.