Pertussis remains one of the most frequent vaccine preventable diseases worldwide. Pertussis is still an important infectious disease with high morbidity and mortality worldwide, especially among infants in whom it is one of the leading causes of mortality. Although most often a persistent but relatively benign respiratory illness, pertussis can result in serious consequences, such as pneumonia, seizures, encephalopathy, and death, especially among infants. Despite high immunization rates in infants and children in many countries, pertussis remains endemic, with epidemics superimposed every 3–5 years [1
]. Although the inception of childhood pertussis immunization programs has significantly reduced the occurrence of the disease in children, waning vaccine-induced immunity from the old vaccine permits the disease to affect adolescents and adults (after about 7 to 20 years from natural infection and 4 to 12 years from immunization), who in turn transmit the disease to nonimmunized or incompletely immunized infants who are more vulnerable to disease-related complications and higher mortality [4
]. Moreover, there is a clear lack of awareness regarding loss of immunity and occurrence of the disease in older patients.
In recent years, acellular pertussis vaccines have been incorporated into the immunization programs of many developed countries, gradually replacing whole cell vaccines. The whole-cell vaccine has been initiated in the Greek national vaccination schedule since 1951, whereas the acellular type since 1997. In Greece booster vaccines were firstly used by doctors of the private sector but were incorporated in Greek national vaccination schedule in 2008. According to the Greek national vaccination schedule, children are immunized compulsory at ages 2, 4, 6 months and with two booster doses at 15–18 months and at 4–6 years old with a diphtheria, tetanus, and pertussis (DTaP) vaccine [6
]. DTaP is also part of four childhood combination vaccines that include other vaccines (e.g., IPV, Hib, HepB). In 1998 the vaccine coverage for pertussis (three doses) in Greece at two years of age was 82% in relation to 82–99% in other European countries [7
]. According to a survey on vaccination coverage conducted by the National School of Public Health in 2006, the percentage of vaccinated children against pertussis reached almost 99% for the first three doses, 98% for the fourth, and 90% for the fifth. Moreover the estimated full DTP coverage (three doses) according to the World Health Organization for the period 2000–2008 was 99% for the Greek pediatric population [8
In the majority of countries where pertussis is a notifiable disease, a case-based national surveillance system is in place. The surveillance of pertussis in Greece is based on notification, which was made obligatory by law since 1950. However, differences in case definitions, methods of diagnosis, and reporting surveillance systems make direct intercountry comparisons difficult. Prolonged cough may be the only clinical feature in adolescents and adults, who may present for diagnosis late or not at all. Even when they present, pertussis clinicians regard it as childhood disease. The general consensus is that pertussis is under diagnosed and underreported [10
]. Despite underreporting, an increased incidence of infant, adolescent, and adult pertussis has been observed worldwide [11
]. This increase has been following the increase in incidence which was observed in 1980s in USA and in the 1990s in Canada and several European countries, despite the high childhood pertussis vaccination coverage and the use of the pertussis vaccine [11
Several studies have suggested that mothers, siblings, adolescents, grandparents, and healthcare workers are a significant source of infection to infants. Most adolescents acquire infection from schoolmates and friends, whereas for adults the main sources are children and work colleagues [5
]. Teachers, healthcare workers, and childcare workers could be at greatest risk of being exposed to and transmitting the disease [22
]. In addition to efforts to improve pertussis immunization rates in children, the expansion of vaccination to target to specific age groups should be considered [23
]. In a recent publication the resurgence of pertussis was related with the emergence of strains producing increased amounts of pertussis toxin [24
We describe the epidemiology of pertussis in Greece and epidemiologic changes throughout a period of twenty-nine years by using routinely collected national surveillance data and data from a tertiary children hospital.