DTaP-IPV/Hib vaccination coverage 2010
Vaccination coverage was calculated on 31 December 2010 on the basis of person-identifiable data from the national childhood vaccination database. The reported coverage provides a minimal estimate, as only vaccinations performed in Denmark by General Practitioners (GPs) are included.
Method of calculation
Vaccination coverage was recorded using the administrative service codes indicated by GPs when settling the first, second and third DTaP-IPV/Hib vaccinations, EPI-NEWS 6/10 and EPI-NEWS 9/10.
In cases where GPs used the same vaccination code at all three vaccinations of the same child, the codes were automatically adapted to include the missing codes.
The numerator is therefore e.g. the number of children born in 2009 who received the initial DTaP-IPV/Hib vaccination and the denominator is the number of children from the birth year residing in Denmark when the data were analysed.
As in previous years, if the codes were settled using one of the parent's civil registration numbers they were subsequently ascribed to the child whose age corresponded to the vaccination in question.
Children migrating in and out of Denmark may affect coverage in either direction. Children leaving Denmark will e.g. reduce coverage, while children previously vaccinated abroad who enter the country will lead to an underestimation of coverage. Finally, any delayed vaccination would contribute to increase coverage over time.
Vaccination coverage for each vaccine is shown by birth cohort in Table 1 and Table 2.
DTaP-IPV/HIB 1, 2 & 3
Among the entire 2010 birth cohort, a total of 68 % had received the first and 49 % the second DTaP-IPV/Hib vaccination.
The lower coverage observed was expected as only children born before 1 October can have received the first DTaP-IPV/Hib vaccination and only children born before 1 August 2010 can have received the second DTaP-IPV/Hib vaccination.
In the birth cohorts 2001-2009, a total of 88-93 % had received the first, 88-92 % the second and 87-91 % the third DTaP-IPV/Hib vaccination.
Coverage has shown a slightly decreasing tendency as from birth cohort 2001 and was at its lowest in birth cohort 2006. As from birth cohort 2007, coverage for all three vaccines has followed a slightly increasing trend.
Coverage for birth cohort 1995-2003 was 80-84 %; the lowest coverage corresponds to birth cohort 2000, the highest to cohorts 1997 and 1998. For the 2005 birth cohort, vaccination was expected not to have been concluded at the calculation date.
DTaP-IPV/Hib 3 coverage for birth cohorts 2007-2009 and DTaP-IPV revaccination coverage for birth cohorts 2003-2005 were generally lower in Copenhagen City, i.e. the municipalities of Copenhagen and Frederiksberg, than in the other parts of Denmark, Table 3.
Undervaccination risk factors
To achieve a more complete understanding of the variations in vaccination coverage, demographic indicators for lack of full vaccination at 18 months of age was analysed among children born in the 2005-2008 period.
Children living in Copenhagen City had a significantly increased risk of not having been fully vaccinated. This undervaccination could not be explained by factors such as origin, mother's age or other family-related conditions associated with undervaccination.
Since birth cohort 2007, a slight increase has been observed in DTaP-IPV/Hib vaccination coverage at 3, 5 and 12 months. The increase is limited, but seemingly consistent. This conclusion is made with the proviso that vaccination has not yet been completed in the younger birth cohorts.
It is possible that increased awareness owing to the introduction of pneumococcal vaccination to the childhood vaccination programme in 2007, EPI-NEWS 19/11, has contributed to a general increase in coverage.
In contrast, DTaP-IPV revaccination coverage has not increased, but remains stable at a level corresponding to revaccination of four in every five children at the age of five years. Coverage in the 2001-2003 birth cohorts (7-9 years of age in 2010) had increased by 1-2 percentage points in the latest statement, EPI-NEWS 9/10, owing to delayed vaccination.
Even though coverage is a minimal estimate, the share receiving DTaP-IPV revaccination is less than optimal.
Physicians and health visitors should pay particular attention to increase the vaccination coverage among children of young mothers and mothers >30 years, children of single parents, children with many siblings and children of non-Danish origin.
Furthermore, it is important to study why vaccination coverage - also that of other vaccines - is somewhat lower in Copenhagen than in the remaining parts of Denmark, EPI-NEWS 18/11 and EPI-NEWS 19/11.
(P.H. Andersen, P. Valentiner-Branth, A. Abou Nader, Dept. of Epidemiology, J.B. Simonsen, Dept. of Epidemiological Research)
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