[Significant decline of the number of invasive Haemophilus influenzae infections in the first 4 years after introduction of vaccination against H. influenzae type B in children].
OBJECTIVE
To evaluate the effect of four years of immunisation against Haemophilus influenzae type b (Hib) on the occurrence of invasive H. influenzae infection and of vaccine failure in children.


METHODS
Descriptive.


METHODS
Through the Nederlands Signalerings-Centrum Kindergeneeskunde (NSCK; Dutch Paediatric Surveillance Unit), invasive H. influenzae infections in children under 15 years of age reported by paediatricians were registered from October 1993 until December 1997. On the basis of the NSCK data the incidence of invasive H. influenzae infections was determined for 1994-1997 in relation to the children's age.


RESULTS
The numbers of cases of invasive H. influenzae infection were 129 in 1994, 41 in 1995, 24 in 1996 and 8 in 1997. The decrease mainly concerned type b infections. The mean age at infection increased in the first two years after the introduction of vaccination. No apparent change in the clinical presentation of infection was observed. In four years of surveillance a total of nine cases of vaccine failure was reported.


CONCLUSIONS
The progressive effect of vaccination against Hib was reflected in the strong decline of the number of invasive Hib infections, mainly in the youngest children. In accordance with the high level of voluntary vaccination in the Netherlands (95.5% as of January 1st 1997) and the expected high vaccine efficacy the number of vaccine failures was low. A further beneficial effect for the youngest children may be expected from starting the vaccination scheme at a still earlier age.
Conyn-van Spaendonck
M A
MA
Rijksinstituut voor Volksgezondheid en Milieu, Centrum voor Infectieziekten Epidemiologie, Bilthoven. mae.conyn@rivm.nl
Veldhuijzen
I K
IK
Suijkerbuijk
A W
AW
Hirasing
R A
RA
D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D006192:Haemophilus Infections / Q000453:epidemiology* / Q000517:prevention & control*; D018073:Haemophilus Vaccines; D019741:Haemophilus influenzae type b / Q000302:isolation & purification*; D006801:Humans; D015994:Incidence; D007223:Infant; D009426:Netherlands; D011159:Population Surveillance; D011639:Public Opinion; D012042:Registries / Q000706:statistics & numerical data; D014611:Vaccination / Q000523:psychology / Q000706:statistics & numerical data / Q000639:trends*
D018073:Haemophilus Vaccines
Sterke daling van het aantal invasieve infecties door Haemophilus influenzae in de eerste 4 jaar na de introductie van de vaccinatie van kinderen tegen H. influenzae type b.