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Clear and present danger: how best to fight the latest whooping cough outbreak

Children too young for the vaccine or those who haven’t been vaccinated are most at risk from whooping cough. anjanettew/Flickr

Even though we’ve had a whooping cough (pertussis) vaccine since the 1950s, the disease is proving difficult to control and beat. Dealing with its resurgence requires clear communication about the importance of vaccination as well as work to understand why we can’t beat this elusive bug once and for all.

In response to the current outbreak of whooping cough, a recent conference in Sydney brought together international and local experts to share the latest information on the impact of vaccinating parents to reduce risks to newborns and progress in developing new pertusis vaccines.

Changing patterns

Whooping cough has killed seven infants in Australia since 2008 and left many more needing hospital care. But efforts to understand the illness must recognise the myriad reasons for the current outbreak.

Vaccine refusal is one part of the cause, but more testing as well as better tests for the disease, the short period of protection, and waning adult immunity are all contributing to whooping cough’s resurgence.

The epidemic we’re in now (2009-2011) is part of a recurring pattern typical of whooping cough, with large outbreaks roughly every three to five years.

But it’s also unique. Compared with epidemics in 1997 and 2002, many more infections have been reported even though there are fewer deaths and roughly the same number of hospitalisations.

The number of cases has only started to fall this year so the public is right to ask why there’s so much whooping cough around despite vaccinations.

Much of the blame has been levelled at vaccine refusers. And vaccine refusal, as well as the tendency for refusers to geographically cluster, certainly promotes the spread of infections.

But Australia has maintained high vaccination rates over recent years, with 94% of two-year-olds completely up to date with their vaccines. And it’s not just communities with high rates of vaccine refusal that are affected by whooping cough.

In fact, most people who get this disease have had at least one dose of the pertusis vaccine.

The rise in detection of cases is partly because doctors are getting much better at recognising mild symptoms and we have more sensitive tests to diagnose the infection. This means people who previously may have been thought to have a viral cough or cold are now being diagnosed with whooping cough.

And other countries are also seeing changes in patterns of whooping cough, both in terms of the age of people getting infected and the number of cases.

Adapting our approach

Before vaccines, it wasn’t uncommon for people to have several bouts of whooping cough infection over their lifetime. And the whooping cough vaccine still doesn’t guarantee lifelong protection from disease, which is why we give booster doses at four years of age and again in high school.

In this most recent outbreak, we saw an unprecedented number of pre-schoolers being infected. So parents have been encouraged to have their children immunised slightly earlier, at three-and-a-half years of age.

Whooping cough, like many other infectious diseases, usually becomes less severe as we grow older. Very young babies – too young to be vaccinated – are at greatest risk of hospitalisation and death.

To try to reduce this risk, authorities have promoted vaccination of groups who are likely to pass the disease on to babies, including parents, grandparents, childcare workers and health-care professionals.

Local and international efforts are helping understand how better to use vaccines to control this troublesome infection. A current national research project funded by the government, for instance, is testing whether giving newborns whooping cough vaccine is safe and will protect them sooner.

Another project is exploring how well newborns are protected if their mothers are vaccinated against pertussis in the second half of pregnancy, a strategy recently recommended by the US Advisory Committee on Immunisation Practices.

Importance of vaccination

Opponents of vaccine programs could argue the ongoing problem with whooping cough despite mass vaccination programs means we shouldn’t bother with the shots. They suggest it’s better to get natural immunity and avoid what they believe is a risky vaccine.

In reality, the whooping cough vaccine is overwhelmingly safe and the unvaccinated are at risk of more severe disease even well beyond infancy. And when they do get whooping cough, they’re likely to have more bugs and spread it more efficiently.

As recently as the 1940s, hundreds of people were dying from whooping cough every year, in a population only a third of the present size. The introduction of whooping cough vaccines in the 1950s changed all that and the vaccine’s contribution to the saved lives must be recognised.

Our vigilance in pursuing this bug stems from the belief that even one death that could have been prevented with a vaccine is too many.

But, we must acknowledge the limitations of vaccine programs and this acknowledgement gives rise to a genuine concern that public confidence in vaccine programs could be undermined or that opponents of vaccinations will amplify such a message or decontextualise it.

This fact shouldn’t discourage clear and rational appraisal of immunisation programs, to further enhance their existing achievements in disease prevention.

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