Effectiveness of 7-valent pneumococcal conjugate vaccine against radiologically diagnosed pneumonia in indigenous infants in Australia.
OBJECTIVE
To evaluate the effectiveness of the 7-valent pneumococcal conjugate vaccine (PCV7) in preventing pneumonia, diagnosed radiologically according to World Health Organization (WHO) criteria, among indigenous infants in the Northern Territory of Australia.


METHODS
We conducted a historical cohort study of consecutive indigenous birth cohorts between 1 April 1998 and 28 February 2005. Children were followed up to 18 months of age. The PCV7 programme commenced on 1 June 2001. All chest X-rays taken within 3 days of any hospitalization were assessed. The primary endpoint was a first episode of WHO-defined pneumonia requiring hospitalization. Cox proportional hazards models were used to compare disease incidence.


RESULTS
There were 526 pneumonia events among 10,600 children - an incidence of 3.3 per 1000 child-months; 183 episodes (34.8%) occurred before 5 months of age and 247 (47.0%) by 7 months. Of the children studied, 27% had received 3 doses of vaccine by 7 months of age. Hazard ratios for endpoint pneumonia were 1.01 for 1 versus 0 doses; 1.03 for 2 versus 0 doses; and 0.84 for 3 versus 0 doses.


CONCLUSIONS
There was limited evidence that PCV7 reduced the incidence of radiologically confirmed pneumonia among Northern Territory indigenous infants, although there was a non-significant trend towards an effect after receipt of the third dose. These findings might be explained by lack of timely vaccination and/or occurrence of disease at an early age. Additionally, the relative contribution of vaccine-type pneumococcus to severe pneumonia in a setting where multiple other pathogens are prevalent may differ with respect to other settings where vaccine efficacy has been clearly established.
O'Grady
K F
KF
Menzies School of Health Research, Charles Darwin University, Casuarina, NT, 0811, Australia. kogrady@menzies.edu.au
Carlin
J B
JB
Chang
A B
AB
Torzillo
P J
PJ
Nolan
T M
TM
Ruben
A
A
Andrews
R M
RM
D000367:Age Factors; D001315:Australia; D015331:Cohort Studies; D005260:Female; D006801:Humans; D015994:Incidence; D007223:Infant; D008297:Male; D022242:Pneumococcal Vaccines / Q000008:administration & dosage* / Q000276:immunology*; D011018:Pneumonia, Pneumococcal / Q000000981:diagnostic imaging* / Q000208:ethnology / Q000517:prevention & control*; D011859:Radiography; D013997:Time Factors; D018074:Vaccines, Conjugate
D022242:Pneumococcal Vaccines; D018074:Vaccines, Conjugate