Paediatric surveillance of pertussis in 1998

Abstract

Doel: Inzicht verkrijgen in de ernst van kinkhoest onder kinderen opgenomen in het ziekenhuis wegens kinkhoest. Methoden: In 1998 werd met behulp van pediatrische surveillance gegevens verzameld van ziekenhuisopnamen. Resultaten: Van de 115 ziekenhuisopnamen was 55% jonger dan 3 maanden en ongevaccineerd; 12% was 3-5 maanden oud waarvan 50% onvolledig gevaccineerd; 33% was 6 maanden en ouder waarvan 61% gevaccineerd. Bij 46% werd de diagnose bevestigd door positieve kweek of PCR; bij 44% door positieve serologie. Drie ongevaccineerde kinderen jonger dan 3 maanden overleden. Cyanose, apneu, zuurstoftoediening, kunstmatige beademing en bradycardie werd vaker gerapporteerd voor ongevaccineerde patienten en de opnameduur was langer (10 versus 4,5 dagen) dan voor gevaccineerde patienten. Hoewel complicaties niet frequent werden gemeld voor gevaccineerden was de enige patient met encephalopathie gevaccineerd. Ook had 17% van de gevaccineerde patienten longontsteking. Conclusie: Het lagere aantal meldingen in 1998 lijkt de lagere kinkhoest incidentie in 1998 t.o.v. 1997 te reflecteren die ook in de routine surveillance van aangiften en positieve serologie werd waargenomen. Evenals in 1997 was kinkhoest het meest ernstig en kwamen complicaties vaker voor bij ongevaccineerde zuigelingen jonger dan 3 maanden. Echter, typische en ernstige kinkhoestklachten kwamen ook onder gevaccineerden voor. Pediatrische surveillance wordt gebruikt om trends uit routine surveillance te verifieren; interpretatie van routine surveillance wordt bemoeilijkt door de nieuwe aangifte-wet en decentralisatie van serologie.<br>

Objective: To gain insight into the severity of pertussis in hospitalised cases. Methods: In 1998, hospitalisation data were collected through paediatric surveillance. Results: From 115 hospitalisation admissions collected, 55% of the patients were younger than 3 months of age and not vaccinated; 12% were 3-5 months of age and of these, 50% were incompletely vaccinated; 33% were 6 months and older and of these, 61% were vaccinated. Fourty-six percent of the patients were diagnosed as having pertussis, confirmed by a positive culture or PCR, and 44% by positive serology. Three unvaccinated cases less than three months old died. Cyanosis, apnoea, administration of oxygen, artifical respiration and bradycardia were more frequently reported for unvaccinated cases compared to vaccinated cases and the hospitalisation time was longer (median 10 days vs. 4.5 days). Although complications were not often reported for vaccinated cases, the only case with encephalopathy was vaccinated and 17% of vaccinated cases had pneumonia. Conclusion: The lower number of reported cases in 1998 seems to reflect the lower pertussis incidence that was also observed in routine surveillance of notifications and cases with positive serology. Like in 1997 pertussis was most severe and complications were more frequently reported in young unvaccinated infants less than three months of age. However, also typical and severe pertussis cases occurred among vaccinated individuals. Active monthly paediatric surveillance is useful to verify trends in routine surveillance; interpretation of the routine sources is hampered by changes in the notification law and decentralisation of serology.<br>