The number of cases of the potentially deadly respiratory disease is now more than 30 times higher than last year, with no end in sight.
Pertussis cases continue to skyrocket around Australia and experts have no clear idea of when the epidemic might end.
And they say the actual numbers are likely to be much higher given many cases go untested and unreported.
Moderating an Immunisation Coalition pertussis webinar this week the group’s CEO Dr Andrew Minton said there had been more than 21,000 cases reported in Australia so far this year.
“If I look at Q2 [this year], which was just under 10,000 and Q3 cases were at 14,300 so you know, it’s almost 50% more, and we still don’t know whether or not we’re over the hump,” he said.
By today that number had risen again by almost 2000 cases to 28,918, according to data from DoHAC’s National Notifiable Disease Surveillance System (as at 12.15pm).
In 2023 there was a total of 2452 cases reported for the entire year.
The case number is well on track to eclipse this century’s record of 38,749 cases, which was recorded in 2011 and was part of an outbreak that lasted three years. This saw 34,833 cases recorded in 2010, and 30,183 in 2009.
In the covid pandemic years of 2021, 2022 and 2023 the annual case tally fell to 550, 483, and 2452 respectively.
So far this year NSW has been the hardest hit, recording 13,766 cases, followed by Queensland (8969), Victoria (4602), South Australia (620), Western Australia (453), Tasmania (284), the ACT (197), and the Norther Territory (27).
More than a third of the national cases so far this year have been in children aged 10-14 years (11,771), with the 5-9 years age group the second highest (5510).
Melbourne GP and coalition member Dr Andrew Baird, who presented the webinar, said there was a theory that epidemics occurred every three or four years but that was not fully supported by Australia’s case numbers. He did warn that the case number had the potential to explode in the later part of this year.
“Two thirds of cases occur in spring or summer, so here comes the sun and here comes pertussis,” he said.
“We note that there was an increase of 500%, so a five-fold increase between 2005 and 2010 and watch this space for how it’s going to increase this year, because we’ve got spring and summer still to come, and we’re already way ahead this year compared to last year.”
Dr Baird said Australia’s pertussis vaccination rates were sitting around 95% for children 12 months of age and two years. That rate dropped slightly to about 94% at age five years, and further in the adolescents’ (11-13 years) to about 87%.
Capturing data for adults is more difficult given that the vaccine is only on the National Immunisation Program Schedule for pregnant women (a single dose recommended for each pregnancy, ideally between 20-32 weeks but at any time up to delivery).
“[For other adults] if it’s not funded, individuals are paying for it,” said Dr Baird.
“And the latest I could get from one of the discount pharmacists was a quote of about $30 per dose for DTPA and $60 per dose for DTPA-plus polio vaccine as well. So individuals who want vaccination as an adult, unless they’re pregnant, are going to have to pay.”
He said older people were particularly vulnerable to serious disease from pertussis and it was recommended that all people over the age of 65 years should be vaccinated. Vulnerable infants under the age of six months are at high risk of severe disease, so all adults who may be in contact with the infants, including the other parent, grandparents and siblings, were also recommended to receive a vaccination.
Dr Baird said pertussis was often mistaken as a childhood disease, but could affect any age.
“Older people tend to get sicker, particularly if they have got one or more comorbidities,” he said.
He said raising vaccination awareness and rates among adolescents and adults were practical actions GPs, public health officials and general practice staff could take.
“All of us have a role in maximising the uptake of all vaccinations, but this vaccination in particular, particularly in adults and older people,” he said.
“It’s become a little bit of a sort of an orphan, and it’s really, it’s our responsibility to pick that up and to help with it.”
He urged practitioners to have a high threshold of suspicion for pertussis when patients presented with symptoms, and to use a PCR to confirm or rule out the disease as a diagnosis.
“Think pertussis, it’s there in all age groups, and vaccinate,” he said.
“And third thing, vaccinate again. It’s not just the primary course, it’s thinking about vaccinating every 10 years. Think about vaccinating in the older people who may not have been vaccinated since they were kids and may not vaccinated at all.”
Associate Professor Paul Griffin, director of Infectious Diseases at Mater Health Services in Brisbane and Associate Professor of Medicine at the University of Queensland Medical School, said testing for pertussis using a PCR was vital during this period when cases were so high.
“For perhaps even the majority of cases, we may not be finding them, because not everybody does get tested,” he told The Medical Republic.
“We have actually recorded a very large number of cases, and it probably doesn’t tell the full story, but also the importance of testing. Finding cases is important. We have antibiotics we can use to treat people, should it be indicated, but also from the public health perspective, in terms of tracking where activity is and being able to respond, finding cases is very important.
“So if people do have potentially compatible symptoms, it is important to go and get that test so we can know what’s going on.”
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Professor Griffin said there “lots of theories” about who pertussis was spreading so virulently in Australia this year. He cited a drop in vaccination – particularly in pregnant women where it was estimated to have declined about 10% – as well as reduced public health measures like hand washing, social distancing and isolating when sick, as some of the key drivers.
“I think there’s a little bit of complacency around these things too, people not being as worried about respiratory infections at the moment, and then the sort of fatigue as come into it as well, talking about covid and then the flu, and then RSV and then mycoplasma,” he said.
“I think people are just a bit over having to have this is a consideration. But the number of cases does highlight that we need to do more. And I think it’s that the public health response, the communication of the risk and recommending the right interventions, including, testing, isolating and particularly vaccinating.”
