Vaccine 26 (2008) 3277–3281 Contents lists available at ScienceDirect Vaccine journal homepage: www.elsevier.com/locate/vaccine Effectiveness of a 2+1 dose schedule pneumococcal conjugate vaccination programme on invasive pneumococcal disease among children in Norway Didrik F. Vestrheim ∗ , Øistein Løvoll, Ingeborg S. Aaberge, Dominique A. Caugant, E. Arne Høiby, Hilde Bakke, Marianne R. Bergsaker Division of Infectious Disease Control, Norwegian Institute of Public Health, Norway article info Article history: Received 6 March 2008 Received in revised form 28 March 2008 Accepted 31 March 2008 Available online 18 April 2008 Keywords: PCV-7 Invasive pneumococcal disease Vaccine coverage abstract The 7-valent pneumococcal conjugate vaccine (PCV-7) was licensed in Norway in 2001. In July 2006, PCV-7 was introduced in the Norwegian Childhood Vaccination Programme in a 2+1 dose schedule, with immunizations administered at 3, 5 and 12 months of age. PCV-7 was offered through the vaccination programme to all children born from January 2006, i.e. a catch-up for children aged 3–6 months. Prior to 2006 the use of PCV-7 was negligible. The effectiveness of the PCV-7 vaccination programme was assessed using data on invasive pneumococ- cal disease (IPD) incidence obtained from the Norwegian Surveillance System for Communicable Diseases, serotype distribution from the National Reference Laboratory for Pneumococci, and vaccine coverage and vaccination status from the Norwegian National Vaccination Register. Vaccine coverage quickly reached high levels; 95% of children >3 months born from January 2006 had received at least one immunization with PCV-7. The incidence rate of IPD among children <2 years rapidly declined; the rate of vaccine serotype IPD in this age group fell from an average of 47.1 cases/100,000 population in the 2 years prior to PCV-7 introduction to 13.7 cases/100,000 population in 2007. The incidence rate of nonvaccine serotype IPD remained stable. The vaccine programme effectiveness was estimated to be 74% (95% CI 57–85%). No vaccine failure was seen after complete primary immunization with two vaccine doses. Our findings indicate that PCV-7 provides highly effective protection against vaccine serotype IPD when administered in a 2+1 dose schedule. © 2008 Elsevier Ltd. All rights reserved. 1. Introduction A 7-valent conjugated pneumococcal vaccine (PCV-7) intended for use in children has been shown to be highly efficacious against invasive pneumococcal disease (IPD); a vaccine efficacy of 97.4% has been demonstrated when the vaccine is administered to infants in a four-dose regimen with three primary immunizations during the first year of life, and a booster in the second year of life [1]. PCV-7 was licensed in the United States in 2000, and a significant decline in IPD incidence rates among children under 2 years old was observed already in 2001 [2]. The decrease in IPD incidence rates extended beyond the target population to older children, adults and elderly persons [3,4]. Conjugate vaccines reduce nasopharyn- geal carriage of Streptococcus pneumoniae belonging to the vaccine serotypes, i.e. serotypes 4, 6B, 9V, 14, 18C, 19F and 23F, leading to a ∗ Corresponding author at: Division of Infectious Disease Control, Department of Bacteriology and Immunology, Norwegian Institute of Public Health, PO Box 4404, Nydalen, NO-0403 Oslo, Norway. Tel.: +47 21 07 64 65; fax: +47 21 07 65 18. E-mail address: didrik.frimann.vestrheim@fhi.no (D.F. Vestrheim). reduced transmission and, subsequently, to herd immunity [5]. At least twice as many cases of IPD are prevented indirectly by herd immunity as by the direct effect of vaccination [4]. Ninety-one serotypes of pneumococci are currently known [6,7]. PCV-7 covers the serotypes most commonly associated with IPD in children, although the serotype distribution, and thus the proportion of vaccine preventable IPD varies with time and geog- raphy [8,9]. During the 1990s the incidence rate of IPD increased in Norway, as in other Scandinavian countries [10,11]. In the period 1995–2001 the incidence rate of IPD was stable at approximately 19–20 cases/100,000 population, and vaccine serotype pneumo- cocci were responsible for 73% of IPD in children <5 years [10]. However, the incidence rate of IPD caused by macrolide-resistant serotype 14 pneumococci in Norway started to increase in 2002, representing about 30% of cases in children aged less than 10 years by 2005 [12]. PCV-7 was licensed for use in a four-dose regimen, with three primary immunizations and a booster (3+1 schedule). However, the initial effects of vaccination in the United States were observed although complete immunization nationwide could not be per- 0264-410X/$ – see front matter © 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.vaccine.2008.03.087