Why are vaccine preventable disease notification rates important?
Vaccination is one of the most effective public health interventions to prevent disease worldwide. Large-scale immunisation programs, such as the Immunise Australia program, have had a substantial influence on rates of illness from a wide variety of communicable diseases. In Australia, many diseases either do not occur or are extremely rare, as a result of successful vaccination programs (ATAGI 2013). Despite this progress, outbreaks of vaccine preventable diseases (VPDs) can still occur.
The National Notifiable Diseases Surveillance System (NNDSS) compiles information on the incidence of all notifiable diseases in Australia. The quality and completeness of data compiled in the NNDSS are influenced by multiple factors. Therefore, the proportion of diagnosed cases of a particular disease that is notified to health authorities is not known with certainty and may vary among diseases, between jurisdictions and over time.
Do rates vary across population groups?
In 2013, the most commonly notified VPDs were laboratory confirmed cases of influenza (commonly known as the flu), varicella zoster infection (also known as chicken pox or shingles) and pertussis (also known as whooping cough).
In 2013, for influenza (laboratory confirmed) there were 81 notifications per 100,000 young people aged 12–24 years. The notification rate was 1.5 times as high among 12–17 year olds as 18–24 year olds (100 compared to 67 per 100,000). The rate for males was a little lower than for females (74 compared to 88 per 100,000) and was also lower for Indigenous than Other Australian young people (60 compared to 82 per 100,000).
In 2013, the notification rate for varicella zoster infection was 56 per 100,000 for all young people. The notification rate was slightly lower for 12–17 year olds than 18–24 year olds (54 compared to 57 per 100,000). The rate for males was a little lower than for females (53 compared to 58 per 100,000) and Indigenous young people had lower notification rates than Other Australian young people (44 compared to 56 per 100,000).
In 2013, the pertussis notification rate was 39 per 100,000 for all young people. Notification rates were 3 times as high among 12–17 as 18–24 year olds (63 compared to 21 per 100,000). The difference between males and females was less pronounced (35 compared to 43 per 100,000). Indigenous young people had lower rates than Other Australian young people (24 per 100,000 compared to 39 per 100,000).
Has there been a change over time?
Following the 2009 pandemic, when the influenza (laboratory confirmed) notification rate rose to 462 per 100,000 young people, the rate dropped sharply to 67 per 100,000 young people in 2010. Since then, it has fluctuated, increasing to 152 per 100,000 in 2012 before declining to 81 notifications per 100,000 in 2013. Similar trends are observed across population groups for age, sex and Indigenous status.
There have been increasing notification rates for Varicella zoster infections among young people over recent years, with rates increasing between 2009 and 2013 from 41 to 56 per 100,000. This trend is largely conserved across different population groups for age, sex and Indigenous status. However, this upward trend has been attributed, at least in part, to the increased awareness of the requirement to notify cases and diagnostic laboratory testing by healthcare practitioners (NNDSS 2012). Since 2006, three categories of Varicella zoster infections have been made nationally notifiable diseases, and by 2009 all jurisdictions were notifying these cases to the NNDSS with the exception of NSW (NNDSS 2012).
There were numerous cases of pertussis associated with the Australia-wide epidemic which began in 2008 and peaked in 2010 (NNDSS 2012). Since 2010, the notification rate for all young people has declined from 111 to 39 per 100,000. These trends are consistent across all population groups for age, sex and Indigenous status, although 12–17 year olds had notably higher notification rates than 18–24 year olds between 2007 and 2011.