“Protect your world – get vaccinated.” That’s the message that the World Health Organisation (WHO) hopes to spread. However, in Australia an old debate has been reignited surrounding a parent’s right to choose whether or not to vaccinate their child. Dr Steve Hambleton, President of the Australian Medical Association, has suggested that parents who choose not to vaccinate their children should be penalised and even face difficulties in enrolling their children at school.

These comments come in the wake of new data which indicates that immunisation rates are falling across Australia. The national average of babies who are fully vaccinated stands at around 92%, one of the highest rates in the world. However, there is wide variation across the country. For example, the number of one-year-olds fully vaccinated in Eastern Sydney stands at 84%, whilst the Great South Coast region of Victoria boasts a more impressive rate of 95%.

The significance of this geographical disparity would imply that a sizeable proportion of the Australian public are not protected by herd immunity. Herd immunity can be described as the level of disease resistance of a community or population. In a population with high levels of immunity to a contagious infection, the introduction of that pathogen will result in lower levels of infection than it would if it were introduced to a population with less immunity. In effect, the immune status of the greater population has the ability to protect the few with no immunity to the introduced pathogen.

The notion of herd immunity is an important one to consider. Some members of the population either can’t be fully immunised, or will have a less than ideal response to vaccines. This includes people who are taking immunosuppressants or chemotherapeutics, those with immunosuppressive illnesses, and those who are still too young to be fully vaccinated.

Unfortunately, it is these population groups; the very young and the very ill, who are often the most likely to suffer the more severe end of a disease’s spectrum. In addition, there is always the fact no vaccine will be 100% effective.

The level of herd immunity required to effectively control the transmission of infection amongst a population varies for each disease. This threshold is dependent upon factors such as the virulence of the pathogen and the route of transmission. Diphtheria and rubella have a herd immunity threshold of around 85%, whereas pertussis has a threshold of up to 94%.

Thinking back to our national average vaccination rate of 92%, and allowing for the lower levels seen in places like Eastern Sydney, we can see that much of Australia is at risk of a pertussis outbreak, with many communities even falling short of the threshold required to halt the spread of diphtheria and rubella. Unfortunately, our disease notification rates reflect these figures with a staggering 34,793 pertussis notifications in 2010.

This alarming figure is one of the highest rates for pertussis notifications in the world. Despite having a pertussis vaccine on the childhood schedule for over 50 years, notifications have continued to increase over the past decade. Pertussis is highly contagious, as reflected by its high threshold for herd immunity.

To compound the problem, immunity provided by the pertussis vaccine wanes after 4-12 years. Consequently, unless the entire population commits to regular boosters, herd immunity will not provide adequate protection against this disease.

Notification rates don’t tell the whole story though, as current evidence shows that pertussis infections in those vaccinated generally result in less severe disease.

Other confounding factors in this upward trend in notifications could include improved detection methods and the emergence of a new genotype of B. pertussis which the vaccine provides poor protection against. Research into strategies to reduce the impact of pertussis in Australia is ongoing.

In the future we may see vaccine formulation changes, or changes to the recommended scheduling of vaccines.

It is worth noting that herd immunity is only relevant to contagious diseases. Tetanus, for example, is acquired from endospores which can be found in soil. As a result of this non-human reservoir of infection, it is only an individual’s level of immunity – not the community’s – that will provide protection.

The advantages of vaccination programs are abundantly clear; from the complete eradication of smallpox in 1979 to the current day where we teeter on the brink of a world free from polio. The WHO estimates that between two and three million lives are saved each year from vaccination alone.

Why are we seeing these declining trends in vaccination in a country like Australia, which has one of the most accessible vaccination programs in the world and, more importantly, what can we do to help?

The decline in the rate of vaccination has been reported in the media to be due to the “Einstein Parent”. These are the parents who question medical authority and often undertake extensive research of their own. In this day and age, the internet offers up a wealth of information, but also a wealth of misinformation. As health promotion is integral to the role of every healthcare professional, it is vital that we provide our patients with reliable information so that the choices they make are informed ones.

To do this we must understand the barriers to vaccination. There have been a considerable number of myths perpetuated by anti-vaccination lobbyists. The Australian Government produces an excellent resource to address these myths entitled, “Immunisation Myths and Realities: Responding to Arguments Against Immunisation”. This booklet is available to download from the Department of Health and Ageing and I would encourage all healthcare professionals to be familiar with its contents.

In addition to the fear-mongering employed by the anti-vaccine camp, there also appears to be a general sense of complacency surrounding many of the serious infections on the vaccination schedule. With the last polio outbreak recorded in Australia in 1956, a parent could be forgiven for thinking that it is unnecessary to protect their child from such an obscure threat.

The same could be said for diphtheria which is virtually unheard of in Australia. However, while these diseases are still active in the world, the risk of coming into contact with “obscure threats” is really only a plane trip away. The death of a 22-year-old Australian woman from diphtheria in 2011 highlights this point particularly well. She was not vaccinated against diphtheria and contracted the disease in Australia from a friend who had recently returned from overseas.

Like any medication, vaccines do have side effects and these should be discussed honestly with patients or their carers. It should be reiterated that the vast majority of these side effects are minor and temporary in nature. Whilst some may argue that it is not ethical to expose a healthy individual to any side effects, vaccination remains one of the most effective means of reducing disease burden. The effectiveness of vaccines in reducing disease is second only to clean drinking water, access to which is considered a basic human right.

Many of the reasons for the declining trends in vaccination rates can be addressed through education and understanding. I would urge you all take the time to acquaint yourselves with some of the common barriers to vaccination. At the same time, it wouldn’t hurt to evaluate our own immunisation statuses, particularly those of us with patient contact.

References:

  1. Swan J, Corderoy A. No Vaccine, No School, Says AMA Chief. Sydney Morning Herald, 11 April 2013.
  2. National Health Performance Authority. Healthy Communities: Immunisation rates for children in 2011-12. Sydney: NHPA; 2013. p5.
  3. Glanze WD. Mosby’s Medical, Nursing, and Allied Health Dictionary. 3rd ed., St. Louis: Mosby; 1990. p754.
  4. National Institute of Allergy and Infectious Diseases. Community Immunity (“Herd” Immunity). Bethesda: NIAID 2010. Accessed 20 April 2013.
  5. Australian Bureau of Statistics. Communicable Diseases. In: Year Book Australia, 2012. cat. no. 1301.0. Canberra: Australian Bureau of Statistics; 2012.
  6. World Health Organisation. Meeting Global Immunization Challenges. Geneva: World Health Organization; 2013. Accessed 20 April 2013.
  7. Post Polio Network. The Late Effects of Polio. North Parramatta: Post Polio Network (NSW) Inc; 2013. Accessed 20 April 2013.
  8. Communicable Diseases Network Australia. Surveillance Report Fortnight 10, 2011. Canberra: Department of Health and Ageing; 2011. Accessed 20 April 2013.
  9. Andre FE, Booy R, Bock HL, Clemens J, Datta SK, John TJ, Lee BW, et al. Vaccine greatly reduces disease, disability, death and inequity worldwide. Bulletin of the World Health Organisation 2008; 86(2): 81–160.

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