Number Of Pertussis Cases Research Articles

Evaluation of pertussis immunity status in schoolchildren immunized with whole-cell vaccine

It has recently been reported that the worldwide increase in the number of pertussis cases is a result of the waning of whole-cell vaccine-induced immunity. Thus, in this study, we aimed to investigate the pertussis immunity status of primary and secondary school students in a district of Ankara, Turkey. A total of 997 healthy students, aged 9-17 years, who had been immunized with four doses of whole-cell pertussis vaccine were included in the study. The subjects were divided into two age groups: 9-14 and 15-17 years. To determine the immune status, serum levels of IgG anti-pertussis toxin (aPT) antibody were tested by in-house ELISA and arbitrarily evaluated as non-immune [< 10 ELISA units (EU)/ml], immune (10-100 EU/ml), and recent infection (> 100 EU/ml). Serum samples of 997 students (559 females, 438 males) aged between 9 and 17 years (mean 13.02 +/- 2.25, median 13 years) were tested. Non-immune, immune and recent infection levels of aPT were found in 27.3%, 59.3% and 13.4% of individuals, respectively. The immune group did not have statistically significant differences between males and females (P = 0.68). In the 9-14 and 15-17 years age groups, serum aPT antibody levels 10 EU/ml were 73.1% and 72.2%, respectively, which did not represent any statistical difference (P = 0.81). Students aged 15-17 years had a higher immunity rate than the 9-14 years group, and the percentage of students with recent infection in the 9-14 years group was higher than the 15-17 years group (P < 0.001). The peak age of non-immunized subjects was 9 years (47.0%), and decreased to a minimum at age 12-13 years, and began to increase again from age 13-14 years. In contrast, the ratio of recent infection was least at age 9-10 years, began to increase, and reached a peak at 12 years, and then decreased. On the other hand, it was observed that household size and monthly income were not associated with the immunity status (P = 0.65, P = 0.37, respectively). The results of the present study show that levels of antibody against pertussis decreased in the younger age groups and, as a result, there is an increase in the number of pertussis cases. Thus, in order to decrease the incidence of pertussis and protect infants, we recommend the application of booster doses at regular intervals.

Impact of Acellular Pertussis Preschool Booster Vaccination on Disease Burden of Pertussis in The Netherlands

An acellular preschool booster vaccination against pertussis has been included in the National Immunization Programme in The Netherlands, since November 2001. We studied the impact of this preschool booster on the epidemiology of pertussis. We analyzed and compared pertussis cases registered in the national notification system, hospital registry, and death registry between the periods 1998-2001 (without preschool booster) and 2002-2005 (with preschool booster). In 2002-2005, the incidence of hospitalizations and notifications in 1-4 year olds were 48% and 44%, lower respectively, than in 1998-2001. Similarly, in 5-9 year olds the incidence of hospitalizations and notifications had decreased 32% and 15%, respectively. In 2005, vaccine effectiveness for preschool booster among children born between January 1, 1998 and January 1, 2001--all of whom had been eligible for the booster--was estimated at 79% (95% CI: 71-85). In infants aged 0-6 months, the incidence of hospitalizations per 100,000 population decreased 40%, from 222.5 to 133.6. In contrast, among cohorts aged 10-19, 20-59, and >60 years, the incidence of notifications increased 60%, 44%, and 68%, respectively. The preschool booster strongly decreased the disease burden in the targeted cohorts. Importantly, the incidence in infants 0-6 months also showed a decline after introduction of the preschool booster, suggesting reduced transmission from siblings to young infants. Meanwhile, the number of pertussis cases in adolescents and adults increased. With prevention of severe pertussis among infants as focus, this effect should not be ignored in the discussion on future vaccination strategies for pertussis.

Two Nosocomial Pertussis Outbreaks and Their Associated Costs—King County, Washington, 2004

Pertussis outbreaks in healthcare settings result in resource-intensive control activities, but studies have rarely evaluated the associated costs. We describe and estimate costs associated with 2 nosocomial pertussis outbreaks in King County, Washington, during the period from July 25 to September 15, 2004. One outbreak occurred at a 500-bed tertiary care hospital (hospital A), and the other occurred at a 250-bed pediatric hospital (hospital B). We estimated the costs of each outbreak from the hospitals' perspective through standardized interviews with hospital staff and review of contact tracing logs. Direct costs included personnel time and laboratory and medication costs, whereas indirect costs were those resulting from hospital staff furloughs. Hospital A incurred direct costs of $195,342 and indirect costs of $68,015; hospital B incurred direct costs of $71,130 and indirect costs of $50,000. Cost differences resulted primarily from higher personnel costs at hospital A ($134,536), compared with hospital B ($21,645). Total cost per pertussis case was $43,893 for hospital A (6 cases) and $30,282 for hospital B (4 cases). Total cost per person exposed to a pertussis patient were $357 for hospital A (738 exposures) and $164 for hospital B (737 exposures). Nosocomial pertussis outbreaks result in substantial costs to hospitals, even when the number of pertussis cases is low. The cost-effectiveness of strategies to prevent nosocomial pertussis outbreaks, including vaccination of healthcare workers, should be evaluated.

Differences of circulating Bordetella pertussis population in Argentina from the strain used in vaccine production

In Argentina, as in other countries, the number of pertussis cases has been increasing, even in highly vaccinated zones. Many reports suggest that the decline of vaccine efficacy due to antigenic shifts in the circulating Bordetella pertussis might be among the factors that contribute to pertussis re-emergence in different parts of the world. To evaluate the incidence of this factor in Argentina, we decided to characterize the circulating bacteria of an important demographic area of this country in comparison with the strain used for vaccine production. From 1997 to 2003 we collected nasopharyngeal samples from pediatric patients with signs of Bordetella infection hospitalized in the metropolitan area of Buenos Aires and La Plata, Argentina. From these samples we identified 28 B. pertussis, which were characterized by biochemical techniques, PCR, DNA fingerprint, prn and ptx genes sequencing, and lipopolysaccharides (LPS) pattern. BOX-PCR from B. pertussis isolates yielded one cluster containing 13 isolates and some smaller ones, being all fingerprints different from the vaccine strain. Differences between Argentinean circulating bacteria and the vaccine strain were also observed for the Prn and Ptx variants as well as for the LPS pattern. Moreover, this last pattern seemed to change over the years. In addition, we identified two B. bronchiseptica. The presence of this Bordetella species together with the observed differences between circulating B. pertussis and the strain used in vaccine production should be considered for the development of an improved vaccine.

Economic Evaluation of an Extended Acellular Pertussis Vaccine Program for Adolescents in Qu??bec, Canada

Pertussis is a frequent cause of cough illness in adolescents. In Canada, immunization against pertussis in public programs has been restricted to children under 7 years of age. The purpose of this analysis was to estimate the health and economic impact of an additional booster dose of the acellular vaccine in adolescents in Québec. We performed a cost-effectiveness analysis, based on a predictive spreadsheet dynamic model following a cohort of 90,929 adolescents in Québec from the age of 14 years over a 10-year period from the Québec Ministry of Health (MOH) and societal (SOC) perspectives. The model was used to compare costs (2003 values) and benefits of an adolescent vaccination program (AVP), including a diptheria, tetanus, and acellular pertussis (dTacp) vaccine administered at age 14 years, with current practice. From the MOH perspective, a booster vaccination of dTacp at age 14 years via the AVP would produce a yearly additional expected cost of Can dollars 1.06 per adolescent with an incremental cost-effectiveness ratio (ICER) of Can dollars 480 per pertussis case avoided based on a 10-year period. When outcomes are discounted at 3%, the ICER rises to Can dollars 527 per discounted pertussis case avoided. From the SOC perspective, the AVP would cost Can dollars 0.83 per adolescent per year with an additional cost per avoided pertussis case of Can dollars 377 (Can dollars 414 per additional discounted case of pertussis avoided). Over the 10-year period, 2012 non-discounted cases of pertussis would be prevented with approximately two hospital admissions averted. This study suggests that administering a booster dose of dTacp at age 14 years to replace the diptheria and tetanus vaccination will slightly increase the economic burden from MOH and SOC perspectives; however, the number of pertussis cases and the number of hospital admissions will decrease.

Economic evaluation of a new acellular vaccine for pertussis in Canada.

Pertussis is a highly contagious infection affecting mainly children. Acellular pertussis vaccines were recently introduced in Canada based on evidence of improved safety and efficacy over whole cell vaccines, the current standard of care. The following study reports the economic impact of replacing the whole cell vaccine (wP) by a new acellular vaccine (aP) in the Ontario pertussis immunisation programme. For a hypothetical cohort of 100,000 children from birth to the age of 8 years, the costs and consequences of pertussis vaccination with either aP or wP were compared. A decision analytical model was constructed for vaccine delivery, treatment of pertussis cases and vaccine adverse events, with analyses from the viewpoints of the Ontario Ministry of Health and society. The main outcomes were expected number of pertussis cases, hospitalisations, and workdays lost by parents. Data on vaccine effectiveness, pertussis incidence, and other parameters used in the model were from published literature. Costs were discounted at 5%, and extensive sensitivity analyses were undertaken. Over 8 years, in a cohort of 100,000 children, the introduction of aP would prevent 10,500 cases of pertussis, avoiding 504 hospital admissions and 73,500 days of work absence. For Ontario, healthcare cost savings over the same period would amount to 275,585 Canadian dollars ($Can), and societal savings to $Can9,752,864

In Reply: Pertussis Immunization

Dr Emerson suggested that the report ignored the distinction between infection and illness when we suggested that adult booster doses would reduce transmission of Bordetella pertussis in adults and could help in the eradication of pertussis in our population. In supporting his suggestion, Dr Emerson has underestimated the number of pertussis cases presently occurring in adults in the United States, has used an unimpressive reference to indicate that adult doses of tetanus and diphtheria toxoids are unnecessary, and has inappropriately questioned the herd immunity concept (the immunization of children at school entry and of adults) in the protection of young children from pertussis.