H. J. Schmitt

Pertussis in adults: frequency of transmission after household exposure

Although pertussis in adults is well documented, opinions differ about incidence of adult disease and about the role of adults as reservoirs of infection. We made use of a prospective household contact study of an acellular pertussis vaccine to collect data about pertussis in adults. All members of families with an index case of pertussis were monitored for respiratory symptoms, and pertussis was confirmed by laboratory tests. In 122 households, 104 children (85%) and 18 adults (15%) were the source of pertussis. These households consisted of 265 adults (aged 19-83 years), in 84 of whom (31%) pertussis was confirmed. Of these 84, 81% had respiratory symptoms for 21 days or more. The spread of pertussis was independent of whether a child (74/104) or an adult (14/18) was the index case. Most adult index cases had no pertussis recall (odds ratio 11.8). The overall attack rate in adult contacts was 0.267 and was independent of the social status and the size of the family and of a pertussis recall, although it differed significantly between women and men (p < 0.05). Erythromycin treatment of the index case reduced the attack rate significantly (p < 0.05). Patients whose first pertussis episode dated back more than 20 years had similar symptoms and attack rates to patients without a recall. We conclude that adults are often involved in the spread of pertussis, and that they can be susceptible to reinfection 20 years after a first pertussis episode.

Evaluation of a Single-Sample Serological Technique for Diagnosing Pertussis in Unvaccinated Children

Abstract This study was performed to evaluate the sensitivity of immunoglobulin (Ig)G and IgA antibodies to pertussis toxin and filamentous hemagglutinin in diagnosing pertussis from a single serum sample. The pertussis group was defined according to the World Health Organization pertussis case definition. The control group coughed for 21 days or more but had no microbiological or serological evidence of Bordetella infection. Both cohorts were divided into infants (<12 months of age), toddlers (1–4 years) and school children (5–10 years). There were 525 subjects in the pertussis group and 321 in the control group, with an even distribution of genders. IgG and IgA antibodies to pertussis toxin and filamentous hemagglutinin were measured in a standardized enzyme immunoassay. Antibody levels beyond the 95 percentile of the control cohort were regarded as indicative of recent contact, setting the specificity level at 0.95. Acute serum samples drawn between 1 week and 3 weeks after the onset of coughing showed a low sensitivity (2–19%) for diagnosing pertussis. In convalescent samples taken 5–10 weeks after the onset of symptoms, detection of IgG anti-pertussis toxin was the best single test, with a sensitivity of 61%, 65%, and 74% in infants, toddlers and school children, respectively. A combination of IgG anti-pertussis toxin and IgA anti-filamentous hemagglutinin using age-specific reference values had a sensitivity of 81–89% in diagnosing pertussis from a single serum sample taken 5–10 weeks after the beginning of symptoms.

Factors influencing the spread of pertussis in households.

The objective of this study was to compare the spread of pertussis in children and adults being secondary contacts after household exposure. The study was nested in an efficacy trial of an acellular pertussis vaccine. The spread of the disease was also monitored with respect to gender and antibiotic therapy. A total of 453 index cases, of which 133 were monitored for adult disease, fulfilled the WHO definition of pertussis. They had contacts to 173 unvaccinated children aged 6–47 months, and a total of 101 adults with pertussis were followed. Detection of the bacteria, or a significant increase of specific antibodies confirmed the diagnosis. Secondary spread of the disease was assumed, when a household member coughed for 7 days or more and had laboratory evidence for pertussis. Crude attack rates (AR) were 69% in children and 31% in adults (P < 0.05). AR in children were independent of gender but more women than men (P = 0.02) were affected in those households where the index case was a child. Erythromycin treatment of the index case reduced the AR in exposed toddlers from 80% to 57% (P = 0.06), and in exposed adults from 40% to 21% (P = 0.2). Erythromycin therapy in contacts did not alter the clinical course of the disease significantly.ConclusionsIn a household study of pertussis, 69% of children and 31% of adults (more women than men) contracted the disease. Erythromycin reduced the number of infections in household contacts, but did not alter the clinical course in those who contracted pertussis.

Economic evaluation of pertussis prevention by whole-cell and acellular vaccine in Germany

Acellular pertussis vaccines are less reactogenic than whole cell pertussis vaccines, but they are also more expensive. Based on simulation models, we compared the costs and effects of three alternative pertussis vaccination strategies in German children to “no prevention”: (1) vaccination with whole-cell vaccine at 45% coverage (vaccine efficacy 90%), (2) vaccination with acellular vaccine at 45% coverage (vaccine efficacy 85%), and (3) vaccination with acellular vaccine at 90% coverage. In the two low coverage scenarios expected annual savings in direct medical costs through prevention of disease were larger for whole-cell than for acellular vaccination (252 vs 216 million DM, respectively). Direct costs for treating the more important adverse events induced by whole-cell vaccination (16.9 million DM annually) did not outweigh the higher direct costs of pertussis infections not prevented with the acellular vaccine and the higher price of the acellular vaccine. However, vaccination with acellular pertussis vaccine rapidly becomes as cost saving as vaccination with whole-cell vaccine as soon as vaccination coverage can be raised from 45% to 52.5% with acellular vaccine. Acellular vaccination is also the superior alternative when considering indirect cost savings resulting from reduction in work-loss due to adverse events.ConclusionIn our simulations, the most cost-effective pertussis prevention strategy was the use of an effective whole-cell vaccine with a high coverage rate. Introduction of the more expensive acellular pertussis vaccines becomes cost saving if at least a 7.5% increase in coverage is achieved. If also non-medical indirect costs to parents resulting from vaccine associated side-effects are accounted for, acellular vaccines may be more cost-effective also in countries with already high whole-cell vaccine coverage.

Wollen wir ein Impfprogramm

wir haben mit dem Impfen in Deutschland viel erreicht. Der letzte autochthone Fall von Poliomyelitis wurde hier im Jahr 1985 dokumentiert. Die Anzahl der Todesfälle durch Diphtherie, Tetanus und Keuchhusten ist von vielen Tausend pro Jahr in der Vorimpfära auf einige wenige Fälle pro Jahr zurückgegangen. Seit 1991 sank die Inzidenz der invasiven Hib-Infektionen von rund 1600 auf derzeit ungefähr 30 pro Jahr. Die Durchimpfungsraten für Säuglinge und Kleinkinder liegen meist über 85 %, Infektionskrankheiten mit hoher Letalität wie etwa die Masern werden von der Bevölkerung nicht mehr als bedrohlich empfunden. Dennoch hatten anlässlich eines Symposiums des Robert Koch-Instituts (RKI) in Berlin verschiedene Redner Defizite beim Impfen aufgezeigt. Deutschland wurde dabei sogar als „Impfentwicklungsland” bezeichnet. Diese Beschreibung wird den Tatsachen nach den eingangs dargestellten Erfolgen natürlich nicht gerecht. Dennoch bestehen – wie kürzlich in einem 10Punkte-Programm des RKI ausgeführt – Defizite. Hierzu zählt vor allem die Tatsache, dass die „letzten 10 bis 15 %” an Durchimpfungsraten fehlen, um den „vollen Erfolg” des Impfens, die Erreger-Eradikation, zu ermöglichen. In diesem Heft wird eindrucksvoll gezeigt, wie die Entwicklungsländer Burkina Faso und der Tschad hohe Durchimpfungsraten erreichen. Der finanziellen und der fachlichen Hilfe von außen bedarf Deutschland natürlich nicht. Was mir dagegen unerlässlich erscheint, ist hier wie dort der politische Wille, Krankheiten zu besiegen und ein konkretes Impfprogramm zu implementieren. In Deutschland gibt es bis heute kein solches Impfprogramm, sondern lediglich Impfempfehlungen. Der wesentliche Unterschied besteht in der Unverbindlichkeit einer (Impf-) Empfehlung einerseits und der Verbindlichkeit, die ein Impfprogramm ausdrückt, andererseits. Um nicht missverstanden zu werden: Eine Impfpflicht wird und kann es in Deutschland nicht geben. Was wir aber benötigen, ist ein