Meryl Dorey’s upcoming Woodford Festival whooping cough trick

At risk of flogging a dead myth it’s worth keeping up deconstructing Meryl Dorey’s falsehoods as they keep arising.

In the near future on radio and most likely at Woodford, Dorey will trot out the old shuffled pertussis vaccination vs notification statistics to argue the vaccine is ineffective. The pertussis trick has been a standard for years but since September 2009, we’ve had access to her data sets when she used them in response to the HCCC regarding complaints raised about her. I’ve looked at each incarnation of this trick, which has scarcely changed.

Her claim begins by pointing out that in 1989-90 just before compulsory notification of pertussis began in 1991, immunisation was 71% (figure 1). This figure is sourced from the top table below, which provides figures from 3 ABS surveys of children 0 – 6 years. [Zoom resolution here].

The bottom table shows that coverage has risen to 95% for the cohort January 1st – March 31st, 2006 in children 2 years and under. It’s from Communicable Diseases Intelligence 2007;31:333. It also informs us the assessment date is June 30, 2008. You can find the same here in Dorey’s submission to the HCCC on page 6.

Figure 1

In replying to the HCCC Dorey referred to the National Notifiable Diseases Surveillance System (NNDSS) figures for pertussis which now includes data to 2011 (Figure 2). [Zoom resolution here]. Her claim continues on, using the two data sources. Although retold countless times, I’ll be scrupulous and quote from Dorey herself on page 6 of her HCCC reply:

Since the AVN was established, Australia has experienced an increase of over 23% in our rate of vaccination against whooping cough with a concurrent increase in the incidence of this disease of almost 40 times. Please refer to the Australian government graphs below:

For our purposes these “government graphs” are figures 1 and 2. Sure enough, as we can see below the notification rate in 1991 is 332 and the rate in 2008 is 14,292. But… 2007 has a rate of only 4,864, 2006 has a rate of 9,764. 2005 has a rate of 11,165. And 1996 (12 years earlier) has a rate of 12, 237.

What we see going back are the peaks and troughs associated with pertussis infection and control familiar to the developed world. We also know the present epidemic began in 2008. Before this, 2007 had the least notifications in eight years. In fact according to this table (pertussis per 100,000) it’s the lowest since 1992.

Figure 2

The operative words here are “concurrent increase”. Ms.Dorey frequently palms this off as a steady, correlating increase in infection when the figures show nothing of the sort. There are many problems with this approach. She is using entirely unrelated data sets. The NNDSS data tell us nothing about vaccination or immunity of subjects. There are 18 age groups in NNDSS data. One of Dorey’s vaccination tables in figure 1 covers two age groups only, the other table covers half of the youngest NNDSS age group.

The 1991 and 1992 notification figures are so low as to be anomalies. This is the normal when a disease is placed on the “notifiable” list and practitioners adjust to new requirements.

But now, let’s return to the ABS pertussis vaccination figures Dorey kindly provided. After a slight drop from the 71% she kindly points out, we reach 2001 – a full decade after notifications began – with a pertussis vaccination rate of only 71.6%. This is most cunning on Dorey’s part.

A 0.6% increase in ten years. Why even bother with the first decade? Why not choose 2001 with a notification rate of 9,541 (almost twice that of 2007)?

Clearly it is rank selection of data to convey a falsehood about pertussis vaccination. Exactly as the HCCC have stated. Applying Ms. Dorey’s logic to 2001 and 2007 vaccination and notification rates one can argue a reduction of almost 50% in pertussis infection, with virtually the same increase in immunisation levels. We can see with rising vaccination there has been no “corresponding increase in the incidence of this disease”.

In fact, we have 71.6% coverage in 2001. And 95% in 2006. Both provided by Dorey. That’s five years, but she chooses to cite the 1990 figure of 70% from the upper table, and the assessment date of June 2008 in the lower table of figure 1. Why? Because the initial year of notification (1991) is absurdly small, and 2008 is the beginning of an epidemic.

Indeed, a close look at notification rates in Figure 2 shows comparable rates in the first and second decades, excluding only the epidemic which began in 2008. Ms. Dorey really needs to explain how these figures can be expected to justify her claim.

Next comes age groups, and our understanding as to why Dorey never mentions them. Most infections in Australia are in adults with no immunity. Her 95% in figure 1 applies only to under 2 year olds. This is half of one age group out of the 18 provided by the NNDSS. We know immunity begins to wane certainly by about age ten (if not earlier) and that adults are definitely in need of a booster. In effect most pertussis notifications are from those with no immunity. Figure 3 is pertussis notifications for 2007 (pre-epidemic) by age and sex [Zoom here]:

Figure 3

In any year (including epidemic years) most notifications come from adults. Rather than pointing to total figures Ms. Dorey should be honest and admit that most infections come from the adult population with an immunisation rate of only 11.3%. See page 18, Adult Immunisation Survey. This is insufficient to provide herd immunity.

Adults may show no symptoms or very mild symptoms and not seek any care. What this means is that adult infection levels are higher than notification levels. It’s important to stress that Meryl Dorey will cite infant or childhood vaccination levels, but most notifications come from adults. Ms. Dorey’s claim of total infections casting doubt on 95% of childhood vaccination is again found wanting.

The fact that 0 – 4 is the highest childhood age cohort and comparable with adults of over 30 is due to newborns being unvaccinated and not completing the schedule for many weeks. This places them at extended risk.

So, even giving Dorey’s dodgy data sets a fair run they still fail on a number of fronts to deliver the goods. In fact they undermine her so-called proof. Infections come from non immunised, and as we’ll see below reduction in childhood immunisation is catastrophic. She has some explaining to do.

We know the pertussis vaccine is not a magic bullet and that vaccinated children can catch pertussis as immunity wanes. In general they develop much milder symptoms and are not at risk of death and disability as are unvaccinated infants and small toddlers. It is crucial to ensure vigilance against waning immunity. Boosters should be considered.

Low immunisation levels have been linked to the present outbreak. Tragically it’s been known for quite some time that this epidemic is likely to have begun in Meryl Dorey’s backyard – where she has her greatest influence. The SMH reported in October 2010:

The highest rates of so-called “conscientious objectors” to immunisation are in parts of the north coast – such as Byron Bay – where 12 per cent of children born between 2001 and 2007 were never immunised for any condition. […]

An epidemic of whooping cough in 2008 and 2009 began on the north coast. It quickly swept across the state driven by low vaccination rates in some wealthy parts of Sydney. Low-income areas in western Sydney also had less immunisation and were linked to outbreaks, Dr Menzies said.

California is also experiencing an epidemic on the back of reduced immunisation levels. Dorey recently posted this Californian article about waning pertussis immunity on Facebook, claiming it indicated an ineffective pertussis vaccine. She omitted Dr. Carol Baker:

In QLD where Woodford holds it’s festival? From November last year. Outbreak in QLD as parents snub vaccination:

PARENTS who refuse to vaccinate their children are contributing to the worst whooping cough outbreak on record in Queensland, with notifications likely to exceed 7000 this year.

Four to 8 per cent of children on the Sunshine Coast are registered as so-called “conscientious objectors”, meaning their parents refuse to immunise them. […] Whooping cough is deadly to babies who are too young to be vaccinated. One in 200 babies who contract whooping cough will die.

The advice from all states and federal health authorities is to immunise and ensure immunity is up to scratch with boosters. The outbreak in Australia is due to low immunisation levels and waning immunity in children who have been vaccinated.

The last person to trust is Meryl Dorey.