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Objectives: To determine the true immunisation status of children identified by the Australian Childhood Immunisation Register (ACIR) as 90 days overdue, and determine why appropriately immunised children were flagged as overdue. Methods: A telephone survey of immunisation providers and/or parents of a stratified random sample of 850 NSW children born on or after 1 January 1996 and identified by the ACIR as 90 days overdue for at least one scheduled immunisation at 17 June 1997. The survey was conducted in June to September 1997. Results: Children in the sample ranged in age from 5 to 17 months. Only 526 (61.9%) could be traced. Of these, 452 (86.6%) were fully immunised, and 75% of immunisations were given on time (within 30 days of falling due). The overall proportion of NSW children identified by ACIR as 90 days overdue who were fully immunised was an estimated 85% (95% CI 82.60-87.4%). For the 452 fully immunised children, a reason for the child's immunisation not appearing on the register could be attributed for only 248/ 452 (54.8%). There was evidence that the provider had failed to submit an encounter form for 141 of these children. Conclusions: In mid-1997, more than half the children identified by ACIR as `overdue' were fully immunised. A significant reason for fully immunised continuing to be flagged as overdue was failure to return encounter forms. Implications: At the time of survey the ACIR could not accurately identify unimmunised children and was of limited use as a tool for public health services to follow up very overdue children. (Aust N Z J Public Health 2001; 25:138-40)

ABSTRACT: To evaluate the efficacy of the mass hepatitis B vaccination program in Taiwan in interrupting perinatal hepatitis B virus transmission, 3464 randomly selected 18-month-old infant vaccinees born to hepatitis B surface antigen-carrier mothers were recruited from 9697 eligible infants during a six-month period of the program. They were divided into ten groups according to maternal infectivity and compliance with the vaccination schedule. Serum samples were tested for hepatitis B surface antigen, antibody to hepatitis B surface antigen, and antibody to hepatitis B core antigen. In 786 infants who had highly infectious mothers and who received hepatitis B immune globulin and vaccine on schedule, the protective efficacy was about 85%. The efficacy seemed to be slightly over in those immunized off schedule. Overall, 11% of infants still carried hepatitis B surface antigen, and 81% of the infants had antibody to hepatitis B surface antigen that exceeded 10 mIU/mL in more than 90% of them. The geometric mean titers of antibody to hepatitis B surface antigen were more than 200 mIU/mL in every group of infants. We conclude that the mass vaccination program is efficacious in preventing perinatal hepatitis B virus transmission and the chronic carrier state; most infant vaccinees have adequate levels of protective antibody at 18 months of age. This program is extremely significant in the control of hepatitis B virus infection in Taiwan.

ABSTRACT: To assess the efficacy of the Haemophilus b polysacchaide vaccine following licensure and to evaluate the risk of Haemophilus influenzae type b (Hib) disease in the week following vaccination, we conducted a day care--based case-control efficacy study using cases of invasive Hib disease ascertained through active surveillance in areas with a total population of 34 million. For each patient 18 to 59 months old, up to three 18- to 59-month-old controls were chosen from the same day care classroom. Using conditional logistic regression, the vaccine efficacy was estimated to be 45% (95% confidence interval = - 1% to 70%) and did not change significantly after accounting for potential biases. In addition, three (3%) of 104 patients vs five (2%) of 207 controls were vaccinated within seven days before the patients' dates of admission (odds ratio = 1.8, 95% confidence interval=0.3 to 10.2), which does not suggest an increased risk of Hib disease in the week following immunization. This study suggests that the efficacy of the currently used HBPV is less than expected from previous studies and points out the usefulness of case-control studies for monitoring vaccine efficacy following licensure.