16 September 2010

A numbers game

Cosmos Magazine
Vaccines have vanquished diseases and saved millions of lives. But a growing band of parents, fuelled by exaggerated fears and outright misinformation, are now reopening the door for known killers.
Herd immunity

We depend on each other to keep society free from many deadly diseases. Do you know which of your friends or family aren't vaccinated? Credit: iStockphoto/Lucy Glover

In October 1977, Variola minor – one half of the most feared viral threat in human history – was cornered in a small port city in Somalia. Its back was against the Indian Ocean and it had nowhere left to run.

Some 200 years earlier a vaccine had been developed against Variola, better known as smallpox. Now, a ring of immunity, created by global mass vaccinations, was closing in. The virus erupted into a characteristic boil on its final victim and then – unable to infect anyone else – vanished.

The immunisation effort has been called the most successful public health battle of all time – smallpox is the only disease eradicated from the natural world to date – and is a testament to the power of vaccines.

But more than three decades later, vaccines are under siege. Previously preventable diseases are popping up more often than before and escaping into the population more frequently than usual. Children are dying of diseases we thought we’d left behind in the 20th century.

So why are vaccines, the heroes of modern medicine, beginning to fail us?

Vaccines are based on the idea that exposure to a weakened or destroyed version of a disease-causing agent trains your immune systems to recognise it. Your body easily fights off the ‘watered-down’ version of the disease but carefully marks its newfound foe. When the real thing comes along, your immune system immediately recognises the invader and declares war.

In this way, it was hoped that vaccines would purge the world of a host of diseases. With no infectable people, they would disappear as smallpox did – and the plan has been mostly successful. In most developed countries, some of the great villains of the 20th century, such as measles and polio, are now rare, seen only in infrequent outbreaks that are soon contained.

Unfortunately, not all vaccines are created equal and not everyone can be vaccinated effectively. So more often than not, when a disease is cornered, it will find a crack in the wall of immunisation and disappear into a vulnerable person. Inside this sneezing, coughing victim, a disease can travel to new cities and come into contact with countless people – including others who are unprotected against it – and evade capture.

Take whooping cough, caused by the bacterium Bordetella pertussis. Australia is in the grip of a whooping cough epidemic: the number of reported cases nationwide almost tripled between 2007 and 2008, with 14,524 people affected. Through 2009 and into early 2010, the number of infections has continued to increase.

And it’s not just Australia – the rates of whooping cough infections in California are the highest in 50 years.

Whooping cough may not sound too severe, but last year three Australian infants died of the disease. In California, five babies died in the first six months of 2010.

The bacteria causes such severe infection that its victims cough violently, unable to catch their breath, causing the trademark ‘whoop’. Most children will survive this onslaught, but they can be left with brain damage from the coughing fits.

So what is causing these outbreaks?

“It’s certain from our perspective that the communities worst hit by this Australia-wide outbreak are those with low vaccination rates and with community attitudes that are at best dismissive – and at worst antagonistic – towards vaccination,” says Paul Corben, director of public health in the North Coast Area Health Service of New South Wales.

His claim is supported by a 2009 study in the Official Journal of the American Academy of Paediatrics, which showed that unvaccinated children are 23 times more likely to get whooping cough.

It’s true that whooping cough vaccine is one of the least effective, and therefore there are natural spikes in the number of cases every two or three years. However, the latest spike in New South Wales is the highest in years, and sustained. The cause is hard to identify, says Peter McIntyre from the National Centre for Immunisation Research and Surveillance at the New Children’s Hospital, University of Sydney.

While vaccination schedules have changed and there are regions with low immunity to the disease, there is also a new, cheap, easy and accurate swab test being used by doctors, he says, which could mean more cases are being reported even though actual incidence has not increased to the same extent. Still, Corben believes this doesn’t account for the difference in the number of cases in certain regions of New South Wales.

“Byron Bay has a low vaccination rate against whooping cough compared to its neighbouring shire, and it experienced double the rate of infection. Bellingen has much lower vaccine coverage than neighbouring Coffs Harbour, and there were threefold more cases of whooping cough there. The statistics are clear and frightening.”

Unfortunately, whooping cough is not the only vaccine-preventable villain breaking out. Measles rates in Australia are climbing for the first time in decades, and there are (so far) contained cases cropping up frequently around the country.

Measles has been eliminated from Australia, but it often returns, brought in by travellers – although there are normally no more than 100 cases a year. In the first three months of 2009, there were 78 reported cases. This year, there have already been outbreaks in Queensland and Perth.

Measles is caused by a Morbillivirus and results in a severe fever, a cough and often a rash. There is no treatment and, particularly in young adults, the disease can cause complications such as pneumonia, brain damage, deafness, blindness and death.

Unlike the whooping cough vaccine, the combined measles vaccine is around 90% effective, and so the increase in the number of cases is alarming.

The measles vaccine is given with the vaccinations for mumps and rubella in a single injection – known as MMR – at one year of age and again when the child turns four. But immunisation rates are down: in fact, they are the lowest for seven years.

The World Health Organisation’s local target is to have 90% of children immunised against measles by age four. Today, only 83% of Australia’s five-year-olds are protected.

Complacency and fear are the two main reasons for this drop in vaccination coverage, according to Chris Ingall, a paediatrician at St Vincent’s Private Hospital in Lismore, New South Wales.

“There’s a lot of fear of vaccines that’s really not rational,” says Ingall, who treated Dana McCaffery, one of the three babies who died of whooping cough in 2009.

“Vaccines are not perfect – you will always get some side effects – but the benefits far outweigh the risks,” adds Ingall. “Vaccines today are safer than ever, yet a lot of anti-vaccination groups only choose the data they want to get their message across, and cut out the rest of the picture.”

When parents hesitate they’re not only imperilling their children, but everyone else’s, he says. “People who have concerns about the safety sometimes postpone vaccination. That doesn’t just affect their family, it affects the whole community and can have tragic consequences. That delay in vaccination can kill people.”

Things are made worse by the wild and unscientific claims that abound online; people who might once have been vaccine ‘fence-sitters’ are deciding to forego vaccination altogether. A 2002 University of Sydney study published in the Archives of Disease in Childhood found that when ‘vaccination’ and ‘immunisation’ are searched for on sites such as Google, 43% of results displayed are ‘anti-vaccination’ sites.

Many try to present themselves as credible scientific bodies, yet they refer to self-published work or incomplete references, according to the study.

“Countering the negative spin that’s out there is a significant challenge,” says Corben. “A lot of the reassuring information about vaccines is targeted at health professionals, and not at everyday families, and that’s something that we’re trying to address.”

Ingall and Corben both cite the Australian Vaccination Network (AVN) – a high-profile anti-vaccine lobby group – as a factor deterring people from vaccination.

“The AVN is very active in the community and quotes disproved links between vaccination and a range of other childhood illnesses,” says Corben.

Former AVN president Meryl Dorey declined to speak to Cosmos, but has been quoted by other media outlets as saying the dangers of vaccines outweigh the benefits. In the past, she has provided inaccurate or incomplete references to back up her claims.

However, the AVN’s slick website can be appealing to parents searching for advice. Its Living Wisdom magazine mixes anti-vaccination articles with stories on “natural health, organic living, instinctive parenting and global awareness”. Its TV ad gives the impression the AVN is quasi-official, asking people who vaccinate their children and note “a reaction” to call their hotline.

Jenny Royle, a paediatrician who works with the immunisation service at Royal Children’s Hospital in Melbourne, believes the only way to counter anti-vaccine feelings is with open and honest communication: “It’s very unusual for people who are fully informed about the risks of the diseases and the vaccines to choose not to vaccinate.”

There are two main approaches to making vaccines: ‘live’ or ‘dead’. And within those categories there are various types of vaccines that each come with a different level of risk.

Attenuated or ‘live’ vaccines contain whole micro-organisms that have had their virulent parts disabled. Killed, component and toxoid vaccines all contain either a dead micro-organism or only parts of the disease-causing agent. These have fewer risks, but often provide less effective immunisation and require boosters.

All vaccine types trigger the body to make antibodies specific to the disease-causing agent, training the immune system to recognise and destroy the disease as soon as it enters the body. Side effects range from swelling at the site of injection to fever. On rare occasions, there are more severe effects.

“The biggest risk is anaphylaxis [a severe and sudden allergic reaction that can result in death] and that can happen with any vaccine that you give,” says Royle. “But this is very rare and can be treated by doctors. To minimise the risk, doctors should always monitor patients for 15 minutes after the vaccine [is administered].

“All medications have a potential side effect, even paracetamol … it’s not something you should hide, that just makes the situation worse. In my experience, when people are fully informed, they still find the benefits of a vaccine great enough to be worth the risks.”

Yet, the better a vaccine performs, the less people remember why it was needed in the first place. UNICEF credits vaccines with saving 20 million lives over the past two decades.

Anti-vaccine groups frequently argue that improvements in hygiene, nutrition and standards of living are responsible for saving these lives and reducing the spread of vaccine-preventable diseases.

While it’s true that hygiene and a high standard of living reduce the mortality rate of diseases, there is no evidence that these factors can control outbreaks without vaccines, says McIntyre.

“The meningitis vaccine only started to be used in 1993 and, within four or five years, we went from having hundreds and hundreds of kids having the disease every year to just a handful,” he points out. “It’s very hard to argue that sanitation or standard of living in Australia has improved so much in the past 15 years to have almost wiped out meningitis.”

Other anti-vaccine arguments are that the injections are not ‘natural’ and don’t offer as long-lasting immunity as being infected with a wild disease. This argument often accompanies the assumption that babies who are infected with vaccine-preventable diseases receive a milder version of the illness than individuals who contract them for the first time in adulthood, says Royle.

She believes people have forgotten how severe the diseases we’re protecting children against can be – even if non-fatal – and explains we still can’t test for them and treat them in time to prevent damage.

“The diseases we’re trying to prevent are important, scary diseases. Every baby has a right to be protected,” she says.

“We have had enviably low levels of measles in our country, but we can’t be complacent. Some of our [geographic] neighbours have very high levels of measles and there is potential for an outbreak in Australia.”

And when there are so many diseases out there that we can’t prevent, why risk infection from the ones we can, asks Royle. “Prevention is still the best cure,” she adds.

And in many cases, it’s the only cure. We still don’t have significantly better treatments for the majority of these diseases than we did in the 1970s.

Populations of unvaccinated children, such as those clustered in Byron Bay and Lismore, are a potential honeypot for viruses and bacteria we may think we’ve vanquished, but which in truth merely await a chance for their return.

While the diseases are still as dangerous, things have changed since scientists eradicated smallpox: the foe then was a virus that killed up to five million people a year. Now vaccines are up against unfounded fears and complacency. What scientists fear is that nothing but an outbreak of a true villain will shake us into recognising the value of vaccines again.

POSTSCRIPT: Why I wasn’t vaccinated

When it comes to anti-vaccination arguments, I have some personal insight: until I wrote this article, I had never been innoculated with the vaccine for measles, mumps and rubella (or MMR).

It’s not that I personally objected, nor that my mother was strongly anti-vaccination; she just wasn’t sure if it was safe or really necessary. Two decades ago, there were rumours that the MMR vaccine was linked to a host of other conditions and could even cause the onset of other ailments. Thinking she was erring on the side of safety, she decided that letting nature take its course was a better option.

She’s not alone. According to Ingall, declining rates of immunisation have less to do with parents turning strongly against vaccination, and more to do with the uncertainty that is triggered by unsubstantiated rumours.

While researching this article and after reviewing the pros and cons, I finally received my MMR vaccine at the age of 24. I wasn’t just concerned about my own health: I didn’t want to be a Trojan horse that put others at risk. As a potential carrier, I’d not only be endangering people who have certain types of cancer or are HIV-positive, but infants less than six weeks of age.

Around 10% of Australian adults aren’t fully vaccinated. And it makes me wonder: how many friends and relatives handling newborn babies are aware of the risk they pose to the bundle of new life in their arms?

Fiona MacDonald is the assistant editor of Cosmos.

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