The epidemiology of pertussis in Germany: past and present

Abstract

Background: Current 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.

Methods: Available 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.

Results: Routine 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was recommended in the German Democratic Republic (GDR) from 1964 and in former West German states (FWG) from 1969, but withdrawn from 1974-1991 in FWG.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.

Conclusion: The 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.

Figure 1

Incidence of notified pertussis illness (1947–2007) and hospitalizations (1993–2007) in Germany, (GDR: German Democratic Republic, FEG: Former East Germany, FWG: Former West Germany).

Figure 2

Pertussis incidence in former East German States 2002–2007 based on notification data according to state-specific infectious disease surveillance laws.

Figure 3

Age distribution of notified pertussis cases in the former East German States Brandenburg, Mecklenburg Western Pomerania, Saxony Anhalt and Thuringia (Fig. 3a), and Saxony (Fig. 3b) 1995–2007. The total number of cases is shown on top of the bars. Age-specific data for 2000 are incomplete and no age specific data are available for 2001.

Figure 4

Incidence of notified pertussis cases in the former East German States Brandenburg, Mecklenburg Western Pomerania, Saxony Anhalt and Thuringia (Fig. 4a), and Saxony (Fig. 4b), 2004–2007, according to age and vaccination status.

Figure 5

Hospitalizations for pertussis per 100.000 inhabitants according to age and residence in former East (FEG) and West (FWG) Germany, 2002–2007 (Source of data: Statistics of hospital diagnoses, Federal Statistical Office, available at http://www.gbe-bund.de/gbe10/abrechnung.prc_abr_test_logon?p_uid=gast&p_aid=&p_sprache=D&p_knoten=VR&p_suchstring=pertussis.