Seroprevalence of Pertussis in the Netherlands: Evidence for Increased Circulation of Bordetella pertussis

Abstract

BackgroundIn many countries, the reported pertussis has increased despite high vaccination coverage. However, accurate determination of the burden of disease is hampered by reporting artifacts. The infection frequency is more reliably estimated on the basis of the prevalence of high IgG concentrations against pertussis toxin (IgG-Ptx). We determined whether the increase in reported pertussis in the last decade is associated with an increase in the number of infections.Methodology/Principal FindingsIn a cross-sectional population-based serosurveillance study conducted in 2006-07, from a randomly selected age-stratified sample of 7,903 persons, serum IgG-Ptx concentrations were analyzed using a fluorescent bead-based multiplex immuno assay. In 2006-07, 9.3% (95%CI 8.5-10.1) of the population above 9 years of age had an IgG-Ptx concentration above 62.5 EU/ml (suggestive for pertussis infection in the past year), which was more than double compared to 1995-96 (4.0%; 95%CI 3.3-4.7). The reported incidence showed a similar increase as the seroprevalence between both periods.ConclusionsAlthough changes in the vaccination program have reduced pertussis morbidity in childhood, they have not affected the increased infection rate in adolescent and adult pertussis. Indeed, the high circulation of B. pertussis in the latter age-categories may limit the effectiveness of pediatric vaccination.

Should acellular pertussis vaccine be recommended to healthcare professionals?

“…In locations with low vaccination coverage, circulation of B. pertussis in the community accounts for natural "boost". However, vaccination leads to a reduction in bacterial circulation and a subsequent loss of protection after natural infection, resulting in an increase in the incidence of the disease among teenagers and young adults, who become an significant source of infection of children 29,30,31,32,33,34,35,36,37,38,39,40 .…”

“…The inclusion of the acellular pertussis vaccine is due to an increase in the incidence of pertussis in certain European countries 28,29,30,31,32,33,34,35,36,37,38,39,40 , the USA 1,78,9,10,11,12,21,24,25,26,27 , Canada 13,22,23 and Australia 16,17,41,42,43 . In these regions pertussis currently affects all age groups, and incidence rates are particularly high in adolescents and young adults 36,38,43 .…”

“…The availability of new diagnostic resources for pertussis, such as PCR and serology, has helped to identify pertussis as one of the main causes of prolonged cough illness in adults 22 and has shown that the disease may exist in mild or asymptomatic forms 33,51 . The large majority of pertussis cases are reported in young babies, but the disease may affect people of any age group, including the elderly 28,39,34,35,37,41,45,47,50,51,56 .…”

“…Seroepidemiologic investigations of the disease conducted in different countries show that the annual incidence of pertussis in adolescents and young adults varies between 1 and 6% 34,35,37,40,44 and that infection rates are greater among HCPs than in other professionals 24 .…”

“…However, HCP vaccination policies vary considerably between different countries 3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19 and have changed over the two last decades due to new information on the epidemiological profile of pertussis and licensing of new safe and effective vaccines for use in adolescents and adults, such as the triple acellular (Tdap) vaccine that, besides protecting against diphtheria and tetanus, also protects against pertussis, and the quadruple vaccine against diphtheria, tetanus and pertussis combined with the inactivated polio vaccine (Tdap-IPV), already licensed in a number of countries 7,8,9,10,11,12,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,…”