Epidemiology of pertussis in Italy: Disease trends over the last century

Abstract

We reviewed the epidemiology of pertussis in Italy over the last 125 years to identify disease trends and factors that could have influenced these trends. We described mortality rates (1888-2012), case fatality rates (1925-2012), cumulative incidence rates (1925-2013) and age-specific incidence rates (1974-2013). We compared data from routine surveillance with data from a paediatric sentinel surveillance system to estimate under-notification. Pertussis mortality decreased from 42.5 per 100,000 population in 1890 to no reported pertussis-related death after 2002. Incidence decreased from 86.3 per 100,000 in 1927 to 1 per 100,000 after 2008. Vaccine coverage increased from 32.8% in 1993 to about 96% after 2006. As for under-notification, mean sentinel/routine surveillance incidence ratio increased with age (from 1.8 in <1 yearolds to 12.9 in 10−14 year-olds). Pertussis mortality decreased before the introduction of immunisation. Incidence has decreased only after the introduction of pertussis vaccine and in particular after the achievement of a high immunisation coverage with acellular vaccines. Routine surveillance does not show an increase in cumulative incidence nor in ≥15 year-olds as reported by other countries. Underrecognition because of atypical presentation and the infrequent use of laboratory tests may be responsible for undernotification, and therefore affect incidence reports and management of immunisation programmes.

Global Childhood Deaths From Pertussis: A Historical Review

“…For high-income countries (HICs), studies were from Argentina [13], Australia [14], Denmark [15, 16], Germany [17], Ireland [18], Italy [19], New Zealand [20], Switzerland [21], the United Kingdom [22–23], and the United States [24–26]. For low- and middle-income countries (LMICs), studies were from Kenya [3, 9], Senegal [8], South Africa [27], and Turkey [28].…”

Pertussis in infants less than 6 months of age and household contacts, Italy, April 2014

“…5 Based on routine surveillance data, Italy is currently a low incidence country and outbreaks or incidence peaks have been rarely reported after the achievement of a high immunization coverage. 6 Even if it is a vaccine-preventable disease, pertussis is still circulating and the need to study the genotypic variation of the bacterium in terms of gene sequencing of pertussis toxin and pertactin, as the main acellular vaccine components, deserves particular interest for the efficacy of vaccine coverage in the population. 7,8 In this report, 4 pertussis confirmed cases, occurred among infants less than 6 months of age, have been described together with the identification of B. pertussis in household contacts of one of them.…”

Pertussis immunity and epidemiology: mode and duration of vaccine-induced immunity

“…The model was initialized in the beginning of 1994, 2 years before the monthly pertussis notification time series commences, coincident with increases in vaccine uptake according to national estimates (Gonfiantini et al 2014), and the switch to aP vaccine (Rota et al 2005; Gabutti & Rota, 2012). Since it is widely considered that the wP vaccine induces immunity similar to that induced by infection, the model does not distinguish between vaccine-derived and infection-derived immunity prior to 1994 (Ryan et al 1998).…”

“…This was ramped up rapidly in the mid-1990s when the country switched to the aP vaccine. Coverage further increased in the first decade of the new century, when vaccines were made available free of charge, reaching an average of 95% by 2009 (Gonfiantini et al 2014). Using recently developed statistical inference techniques (King et al 2015b; Ionides et al 2015), we estimated the values of model parameters needed to explain the dynamics of pertussis incidence over this period of abrupt change in vaccine coverage.…”