Why are children on the NSW North Coast not being vaccinated against chickenpox?

In November 2005, varicella (chickenpox) vaccination administered at 18 months of age was included in the government funded National Immunisation Program for all children born after 1 May 2004.¹ Each month the former North Coast Public Health Unit received a report on children recorded as overdue to receive the vaccination according to the Australian Childhood Immunisation Register (ACIR). It appeared that a disproportionate number of children aged 20–60 months were recorded as overdue for varicella vaccine.

This study explored why 907 children living in northern New South Wales (NSW) and aged 20–60 months as at April 2010 had received, according to the ACIR, all their other due vaccinations but not varicella vaccination.

The parents of children aged less than 5 years and identified as being vaccinated with all other scheduled vaccines except varicella were sent: a copy of their child’s vaccination record; a chickenpox factsheet; a questionnaire; and a letter explaining that their child was overdue for varicella vaccination and highlighting the importance of the vaccination. As this study formed part of routine follow-up of children identified by the ACIR as being overdue for vaccination it did not require ethics approval. This is in accordance with NSW Health Policy Directive PD2005_098.²

The questionnaire included questions asking whether their child had been vaccinated and whether the child had also had chickenpox. See Box 1 for questions.

The ACIR records for all children were checked 12 months after the initial contact.

A total of 406 questionnaires (45%) were returned to the Public Health Unit. More than a quarter of respondents (n = 111, 27.3%) indicated that their child had been vaccinated. This was verified by contacting their providers and updating the ACIR. Fifty respondents (12.3%) indicated that their child had experienced varicella infection and was therefore not vaccinated. Twenty-six of these children were reported to have had the infection before the age of 18 months.

The letter prompted 155 respondents (38.2%) to seek vaccination from their immunisation provider. Three percent of parents (n = 12) indicated that they had not been offered the vaccine by their vaccine provider, while approximately 6% (n = 26) indicated that they would rather their child got “natural disease”. Other reasons for not vaccinating included wanting to wait until the child was older (n = 2), wanting to wait until the vaccine had been around for longer (n = 2) and medical contraindications (not registered with the ACIR) (n = 4). Some parents said that they had forgotten (n = 7).

Twelve months after the intervention, according to the ACIR 501 children (55%) remained unvaccinated and 42 parents (4.6%) had completed a conscientious objector form indicating they did not wish their child to receive the vaccine.

Based on the returned questionnaires and verification with the immunisation provider, many children who had no varicella vaccine recorded on the ACIR had been vaccinated or had experienced self-reported varicella disease. The simple intervention of a letter indicating their child’s status, describing the potential complications of chickenpox and encouraging vaccination, prompted almost 40% of the respondents to have their overdue children vaccinated against chickenpox.

Globally, many families and countries cannot afford to protect their children against varicella and it is not a public health priority in settings where vaccine-preventable pneumonia (pneumococcus), diarrhoea (rotavirus) and measles are common and must remain the focus of immunisation programs.³ However, in Australia, where the vaccine is available free to children, greater effort should be made to encourage parents and providers to optimally protect their children.