No 19 - 2011

PCV coverage and invasive pneumococcal disease 2010

The 7-valent conjugate pneumococcal vaccine (PCV7) was comprised by the Danish childhood vaccination programme since 1 October 2007. The vaccine protects against invasive pneumococcal disease (IPD) caused by 7 pneumococcal serotypes (PS).

IPD cases are defined on the basis of positive culture for Streptococcus pneumoniae from cerebrospinal fluid, blood or other normally sterile material.

As from week 16, 2010, the 13-valent conjugated pneumococcal vaccine (PCV13) was delivered instead of PCV7, EPI-NEWS 15/10.

Vaccinating physicians were encouraged to exhaust their stock of PCV7 before introducing PCV13. The 2010 transition year will be considered a PCV7 year in the following.

Background

PCV7 is given at the ages of three, five and 12 months in the standard childhood vaccination programme. Children, who on 1 October 2007 were aged 4-11 months or 12-17 months, were offered three and two doses, respectively, as part of an introduction programme, EPI-NEWS 37ab/07 (pdf).

Prior to the introduction of PCV7, the seven PS included in the vaccine caused 60-65 % of all IPD cases in children < 5 years of age.

Vaccination coverage

Vaccination coverage was recorded using the administrative service codes indicated by GPs when settling the first, second and third vaccinations. As per 31 December 2010, the coverage of the standard childhood vaccination programme for the birth cohorts 2007-2009 was 85-89 % for the first PCV7 and 86-91% for the second, Table 1.

Coverage of the third PCV7 was 86 % (children born from 1 June and therefore comprised by the childhood vaccination programme) and 88 % for the 2008 cohort.
The 2009 and 2010 birth cohorts had not been fully vaccinated when the data were analysed.

Among children aged 4-11 months at the initiation of the introduction programme, coverage was 76 %, 71 % and 57 % for the first, second and third PCV7, respectively. Among children aged > 12 months 58 % and 51 % had received the first and second PCV7, respectively.

Changes in IPD occurrence

Figure 1 shows the age-specific occurrence of laboratory-confirmed IPD cases per 100,000 inhabitants before and after the introduction to the childhood vaccination programme.

The report is based on national data from the Neisseria and Streptococcal Reference Laboratory, Statens Serum Institut.

The overall IPD incidence before PCV7 was 20 cases per 100,000 (on average 1,055 annual cases). The incidence decreased to 18 cases per 100,000 (on average 982 cases per year).

The decrease in IPD incidence was strongest in children < 2 years: from 54 cases per 100,000 in 2000-2007 to 25 cases per 100,000 in 2008-2010. In this age-group, the incidence of IPD caused by the serotypes included in the vaccine decreased from 37 to four per 100,000 following the introduction of PCV7. This is equivalent to an estimated 87 % programme efficiency against the seven vaccine serotypes, counting vaccinated as well as unvaccinated children.

Among children below the age of five years, mortality following IPD was nearly 2 % in the 2000-2007 period before the vaccine was introduced. After the introduction of the vaccine, the 2008-2010 period has seen a single death among IPD cases below five years of age, corresponding to a 0.6 % mortality. Furthermore, the mean number of notified cases of pneumococcal meningitis in children below the age of five years fell from 23 per year to 13 per year following the introduction of PCV7.

Commentary

The IPD incidence in children < 2 years has been more than halved compared with the average incidence recorded in the eight-year-period leading up to the introduction of PCV7 to the childhood vaccination programme. This is primarily owed to a decrease in the occurrence of the PS included in the vaccine.

A small increase was observed in the IPD incidence of the PS not comprised by the PCV7. Specifically, the increase was caused by PS 7F, 1 and 19A which are all comprised by the currently used PCV13.

PCV coverage is approximately two percentage points lower than that of the DTaPIPV/Hib which is given concurrently. DTaPIPV/Hib coverage will be reported in a future edition of EPI-NEWS.

The somewhat lower coverage corresponds to approx. 1,300 children of the 2008 birth cohort consisting of approx. 66,000 children receiving the DTaPIPV/Hib vaccine but not the PCV vaccine. The cause of this choice not to receive the vaccine is unknown, but the vaccine's efficiency is assessed to be satisfactory at the current coverage.
(P. Valentiner-Branth, J.N. Rasmussen, Dept. of Epidemiology, J. Simonsen, Dept. of Epidemiological Research, L. Lambertsen, H. Ingels, S. Hoffmann, H.B. Konradsen, DBMP)

Individually notifiable diseases and selected laboratory diagnosed infections (pdf) 

11 May 2011