The recent diphtheria outbreak in Australia is a stark reminder of the ongoing challenges posed by vaccine-preventable diseases. This highly contagious bacterial infection, which can cause both skin and respiratory issues, has been making a resurgence in the country, particularly among Indigenous populations. The situation is particularly concerning due to the low vaccination rates and the potential for rapid spread in close-quarter living conditions.
The outbreak, which began in March, has already affected over 130 people in the Northern Territory, with cases also reported in Western Australia, South Australia, and Queensland. This is the largest diphtheria outbreak in Australia in over two decades, and it highlights the fragility of our current vaccination infrastructure. The decline in childhood immunisation coverage, exacerbated by the COVID-19 pandemic, has created an environment where diphtheria can thrive.
Diphtheria bacteria can live in the mouth, nose, or throat, or on skin lesions of infected individuals. It spreads through respiratory droplets during coughing or sneezing, or through close contact with skin lesions. Symptoms of respiratory diphtheria include a sore throat, fever, a grey covering over the tonsils, and enlarged lymph nodes, which can be life-threatening if left untreated. Cutaneous diphtheria, on the other hand, presents as chronic, non-healing sores or shallow ulcers covered by a grey membrane.
Prior to the introduction of vaccines in the 1930s, diphtheria was a leading cause of childhood death globally. Even today, respiratory diphtheria is significantly more deadly, killing up to one in 10 infected people, even with treatment. The recent outbreak has resulted in one suspected death, although the cause is still under investigation.
The spread of diphtheria is being driven by falling vaccination rates and missed booster shots, particularly among special risk groups such as pregnant women. The Australian immunisation handbook recommends the diphtheria vaccine for infants, children, and adolescents, and routine booster vaccination in adults. However, childhood immunisation coverage rates have dropped below the 95% aspirational target, with coverage rates for two-year-olds at about 90%.
Despite these challenges, there is a glimmer of hope. The Australian government, in collaboration with the Northern Territory government and the Aboriginal-controlled sector, is working to increase vaccine access in affected areas. Additionally, the high vaccination coverage among Aboriginal and Torres Strait Islander five-year-olds, at 94.33%, is a positive sign.
The outbreak serves as a critical reminder that vaccine-preventable diseases can re-emerge when immunity gaps exist. It underscores the importance of maintaining protection through timely boosters for adolescents and adults. As we navigate the post-pandemic world, it is crucial to prioritise vaccination efforts to prevent the resurgence of diseases like diphtheria, which can have devastating consequences, especially for vulnerable populations.
