Immunization status and demographic characteristics of New Zealand infants in the first 6 months of life

Predictors of incomplete immunisation in Victorian children

OBJECTIVE

Using probabilistic record linkage, this study aimed to determine the predictors of incomplete immunisation in Victorian children.

METHODS

Records of all births in Victoria in 1998 were linked with records from the Australian Childhood Immunisation Register (ACIR). The outcomes of interest were the predictors of immunisation status at 12 and 24 months of age.

RESULTS

A total of 91.1% of birth records were linked with records from the ACIR (n=55,129). Immunisation coverage was 92.8% at 12 months and 89.2% at 24 months. After multivariate analysis, the following maternal factors were significant predictors of incomplete immunisation in children aged 12 months: higher parity, 12-23 months interval between pregnancies, not being married, Aboriginal or Torres Strait Islander or born overseas, younger age, no private health insurance, home birth, metropolitan place of birth, and being in the highest or lowest socioeconomic quintiles. Low birthweight and singleton birth were also significant predictors. All of these factors were also predictive of incomplete immunisation in children aged 24 months, with the exception of low birth weight, which was only significant in the very low birth weight category. Congenital malformations or prematurity were not significant predictors.

CONCLUSIONS AND IMPLICATIONS

Record linkage is an effective means of determining the relationship between immunisation status and socio-demographic and health-related factors. It enabled small groups within a large population to be studied, confirming findings from previous survey studies and indicating that several population groups were at increased risk of incomplete immunisation. The main limitation of the study was the under-reporting of immunisation status to the ACIR.

Assessment of delay in age-appropriate vaccination using survival analysis

Assessment of delay in age-appropriate vaccination provides more information about timeliness of vaccination than up-to-date vaccination coverage. The authors applied survival analysis methods to data from a vaccination coverage survey among children aged 13-59 months conducted in Argentina in 2002. By age 19 months, 43% of children (95% confidence interval (CI): 40, 46) were vaccinated with the fourth dose of diphtheria, tetanus, and pertussis (DTP4). By age 13 months, 55% of children (95% CI: 52, 57) were vaccinated with measles-containing vaccine. By age 7 months, 33% of children (95% CI: 27, 40) were vaccinated with the third dose of hepatitis B. Compared with firstborn children, third children were more likely to be delayed for DTP4 (relative risk (RR) = 1.41, 95% CI: 1.22, 1.62), measles-containing vaccine (RR = 1.54, 95% CI: 1.32, 1.78), and the third dose of hepatitis B (RR = 1.31, 95% CI: 1.03, 1.67). Children whose caregivers had completed secondary school were less likely to be delayed for DTP4 (RR = 0.68, 95% CI: 0.52, 0.90) compared with those whose caregivers had not completed primary school. Survival analysis methods were helpful in measuring vaccine uptake and should be considered in future surveys when assessing delay in age-appropriate vaccination.

An attempt to swindle nature: press anti-immunisation reportage 1993-1997

There is some evidence that low childhood immunisation rates in Australia may be attributed partly to parental antipathy toward immunisation. The anti-immunisation movement is becoming more organised in its efforts to lobby against childhood immunisation, while the lessening of the public's exposure to the effects of vaccine-preventable disease has provided a climate ripe for such a lobby to have a disproportionate influence on parents. Forty months of Australian print media coverage of immunisation were reviewed for anti-immunisation arguments and their underlying ideological subtexts. Of 2440 articles about childhood immunisation, 115 (4.7 per cent) contained statements opposing immunisation. Eight subtexts that referenced wider discourses about medicine, the state and the body dominated anti-immunisation discourse (cover-up; excavation of the facts; unholy alliance for profit; towards totalitarianism; us and them; vaccines as poisonous chemical cocktails; vaccines as cause of idiopathic ills; and back to nature). Attempts to redress claims made against immunisation must not only address specific claims about vaccine efficacy and safety but be grounded in a reframing of the ideological appeals that currently frame the contents of anti-immunisation discourse.

Characteristics of infants receiving prompt first diphtheria-tetanus-pertussis immunisation in an infant cohort

The Centers for Disease Control in the United States have stated that studies to determine factors associated with failure to receive the first recommended dose of diphtheria-tetanus-pertussis are required. We examined an infant cohort to identify family and infant characteristics predictive of prompt first immunisation, to document changes in prompt first immunisation rates over time and to identify reasons for immunisation delay. The study sample consisted of one-fifth of live births in Tasmania at risk of sudden infant death syndrome. From 1 January 1988 to 31 December 1994, families of 8011 infants (83 per cent of eligible infants) participated in a telephone interview when the infants were a median postnatal age of 11 weeks and 3 days. Prompt immunisation was defined as the report by parents of diphtheria-tetanus-pertussis vaccination before a postnatal age of 10 weeks. The proportion of cohort infants promptly immunised increased (P < 0.0001) over time from 1988 to 1994. Prompt immunisation was associated with various characteristics of the infant and family. The proportion of infants promptly immunised decreased as birth order increased and as the interpregnancy interval between the index child and his or her immediately elder sibling decreased. After exclusion of infants not promptly immunised because of illness, birth order and interbirth interval remained significant predictors of prompt immunisation, suggesting that these factors are acting to increase immunisation delay through pathways unrelated to their potential effect on infant illness rates.

A population-based survey of immunisation coverage in two-year-old children

A cross-sectional, population-based, cluster-sample survey of 187 children was conducted in the Newcastle area to assess the proportion of two-year-old children who were fully immunised, to ascertain whether administration of these vaccines was age-appropriate and to look for factors predicting incomplete immunisation. Parents or guardians were interviewed at their homes and the immunisation status of the children was verified either by the parent-held record or by the immunisation-provider-held record. Levels of full immunisation were 77 per cent at the time of interview and 72 per cent at the second birthday if Haemophilus influenzae type b (Hib) vaccine was excluded. If it was included, the full immunisation level was 51 per cent. Coverage was highest for oral polio vaccine and lowest for Hib vaccine. Twenty-nine per cent of all immunisations were given early, 44 per cent were given on time and 20 per cent were given late. Doses of vaccines due at older ages were more likely to be given late or not at all. Factors predicting incomplete immunisation were: the principal caregiver being aged under 25 years, being born outside Australia, having post-secondary qualifications, being female and having more than one child in the household. Immunisation coverage levels were not high enough to protect against outbreaks of pertussis and measles and cases of Haemophilus influenzae type b. Immunisation providers should aim to increase coverage to protect the population against all vaccine preventable diseases, and aiming at high-risk groups could more effectively do this.