National study of infants hospitalized with pertussis in the acellular vaccine era.
BACKGROUND
In Australia in 1999 acellular pertussis vaccine (DTPa) replaced locally manufactured whole cell vaccine given at 2, 4 and 6 months of age with coverage of about 95% by 12 months of age. Few data are available on pertussis hospitalizations or sources of infection in countries exclusively using DTPa.


METHODS
In 2001 national active monthly surveillance of infant hospitalizations for pertussis was conducted through the Australian Pediatric Surveillance Unit, which surveys all child health specialists monthly. A standard questionnaire was completed for notified cases.


RESULTS
There were 140 infants reported (median age at diagnosis, 8 weeks). The rate of hospitalization in indigenous infants was significantly higher than in nonindigenous infants (P < 0.01). Of 97 (69%) infants who had not been vaccinated for pertussis, 63 (65%) were <8 weeks old (before the first scheduled dose of DTPa vaccine). Of 76 infants age > or =8 weeks, only 28 (37%) were appropriately immunized for age. Of 68 coughing contacts whose ages were known, 46 (68%) were adults, usually one of the infant's parents. Of 32 child contacts 16 (50%) were siblings. Four infants <6 weeks old died.


CONCLUSIONS
Despite universal vaccination with DTPa in Australia, pertussis remains an important cause of hospitalization, morbidity and death in infants, most of whom were too young to be vaccinated or had missed vaccinations. The most common source of infection was a parent. Strategies to improve pertussis control in countries with high DTPa coverage could include adult-formulated booster pertussis vaccines for adolescents and recent parents and/or accelerated pertussis vaccine schedules for infants.
Elliott
Elizabeth
E
Discipline of Paediatrics and Child Health, The University of Sydney and The Children's Hospital at Westmead, Sydney, Australia. apsu@chw.edu.au
McIntyre
Peter
P
Ridley
Greta
G
Morris
Anne
A
Massie
John
J
McEniery
Julie
J
Knight
Geoff
G
D001315:Australia / Q000453:epidemiology; D001886:Bordetella pertussis / Q000276:immunology; D005260:Female; D006760:Hospitalization; D006801:Humans; D007223:Infant; D008297:Male; D010567:Pertussis Vaccine / Q000276:immunology*; D016133:Polymerase Chain Reaction; D011159:Population Surveillance; D022282:Vaccines, Acellular / Q000276:immunology*; D014917:Whooping Cough / Q000175:diagnosis / Q000453:epidemiology* / Q000276:immunology / Q000517:prevention & control
D010567:Pertussis Vaccine; D022282:Vaccines, Acellular