The risks of declining childhood vaccination include a resurgence of dangerous infectious diseases driven by airborne pathogens such as Bordetella pertussis, the bacterium that causes whooping cough (also called pertussis). A recent local news article highlights this and touches on the infection pause as a reason for a 2024 epidemic. But I’m no fan of language like “catastrophic”, and I’m even less of a fan of telling half a story to trigger fear and perhaps scare people into vaccinating. But before we accept the article’s premise, let’s look at what pertussis is actually doing in Australia; it’s not as simple as it looks.

Headlines raising fear

A recent local news article reports a massive rise in whooping cough (also called ‘pertussis’) cases, and it tells two stories.

The first story is about a rebound of cases after the pandemic lockdowns, which created an infection pause (see below), and the second is about an epidemic driven by falling childhood vaccination rates, described as “potentially catastrophic.”

The “Infection Pause”: because it’s about fewer infections, not an immune debt to repay

Overall decline in vaccination rates among the young

According to the Australian Government Department of Health, Disability and Ageing page today…

The rolling annualised percentage of all children ‘fully immunised’ by 12 months of age is 91.54%

Which is further below the last 2024 point on the graph below; the trend of fewer very young children being fully vaccinated continues. To be clear, that is bad news. But is it driving the 2024 pertussis epidemic? As usual, it’s more complex than that.

Are vaccination rates so bad that they warrant being described as “potentially catastrophic”? That doesn’t leave us much wiggle room, does it? “They could all be fine with a bit of work“, through to “We could all be dead!“.

Maybe we could just tone the language down a wee bit?

Vaccination rates are dropping in the first year of life. We had a single year (yep, just the one) at the heady number of 94.85%. Now we’ve fallen back to teh worst ever, right? No. We’re where Australia sat for about 15 years, from 2001 to 2014. We survived that decade and a half, right? Mmmm. Anyway. Further, the second-generation pertussis vaccine is safe and keeps most vaccinated people out of the hospital, but its effectiveness may be waning as the bacterial cause of pertussis continues to evolve.

What we don’t want is a trend of decreasing vaccination uptake, though. Work will be required to arrest and turn that around. I’d recommend a wide-reaching national communication campaign like the wasteful one currently telling you that you will pay less for medicines. I think that may be fairly obvious when you pay for medicines. That’s purely a taxpayer-funded political campaign. I think we could better direct that money into explaining the safety and many short- and long-term health benefits of childhood vaccination.

So what about pertussis in Australia in 2024?

In 2024, there was a very big epidemic of pertussis cases in Australia. Pertussis is due to an easily transmissible pathogen that can be expired from our airways via infectious particles, called Bordetella pertussis. The 2024 epidemic was the biggest on record in terms of cases and rate per 100,000 Australians. No argument. You can see that in the data graphed by year below.

But in 2025, cases and rates dropped a lot in the largest population centres. But not in all jurisdictions. We’ll look at this in more detail soon.

In 2025, many pertussis cases were still reported, but the total number and the rate per 100,000 people were both lower than in some previous epidemics.

This is all to say that a major epidemic followed a three-year pause in infections, bringing pertussis cases to the lowest levels recorded in 30 years.

Immunity waned during that infection pause. Overall vaccination rates among young children also began to slowly decline during this time.

What about pertussis activity across Australian jurisdictions?

The news article focused on children (0 to 14 years of age), so it uses the pertussis rate per 100,000 children (from this report). That choice yields higher numbers than those I use here because most cases involve younger people, whereas my numbers use the total population, which includes younger and older people. I don’t have the granular population data for each age band to hand. I’ve assumed the trends will be largely the same.

A few things about the graphs below, which plot the rate of pertussis cases per 100,000 people in each state or territory (coloured line) alongside the national plot (grey):

• Pertussis normally occurs in epidemics every 4 or so years in Australia. So peaks and troughs of activity are normal and should be expected.
• Epidemics vary in size, but it’s clear from teh graphs that the longer the time between epidemics, the bigger the peak will eventually be – see 2011 and 2024 epidemic peaks.
• Epidemic peaks do not occur at the exact same time everywhere across Australia. Sometimes the rate of cases per 100,000 people in a specific jurisdiction peaks before (pink squares below) or after (red circles) the national rate of cases peaks. Sometimes there’s no obvious local peak, even though there’s a national one (yellow triangles). If this isn’t an error on my part for using the total population instead of focusing on children, then it suggests that it’s pretty normal to see some regions appear to be rising even after a national epidemic has peaked the year before. That’s what we saw in 2025 compared to 2024. It’s shown, but not explained by the multicoloured graph in that news article. But to be clear, it’s not a sign of “catastrophe”.

Are pertussis cases still rising in 2026 in Australia?

No. They are falling. Sure, they’re falling from a very high 2024 peak, but they are falling. More immunity resulting from the top-up of existing immunity through widespread infections in 2024 among the vast majority who are still getting vaccinated will have quelled this epidemic. Some of those infected will not have been vaccinated, but most of them will now also have immunity. They just risked getting a lot sicker and perhaps ending up in the hospital with whooping cough.

What happens next?

We’re continuing to head out of the big 2024 epidemic. Because vaccination is also declining, the timing of the next epidemic peak might be hard to predict. It might take a while for a 4-year pattern to reappear. Some of that depends on Australians’ willingness to return to safe, harm-reducing vaccination.

Patterns in the numbers

This part is just something I thought was interesting.

The year-by-year pertussis epidemic curves above look like a week-by-week epidemic curve (see the next graph) when zoomed in.

Notifications go up, they peak, and they come down. The difference is that the earlier graph unfolded over years rather than weeks. Below is the same Australian notification data, plotted month-by-month. This breaks down the annual epidemics so you can see that they consist of months of rising, peaking, and declining cases. Sometimes one year runs into another, and the cases never return to baseline. After a major pertussis epidemic, it can take one or more years for cases to settle back down.

Here, I’ve zoomed in on the 2020-2026 period to see how few cases there were during the time Australia limited people’s movements and gatherings. Preventing people from exchanging airway contents in poorly ventilated indoor settings can improve our health in several ways, it seems. This graph also shows the curve suddenly taking off in March 2024. The world experienced a pertussis pandemic in 2024, so it’s unsurprising that Australia would also receive infected people from other parts of the world to help kick off our local epidemic.

Next, let’s take a look at total Australian pertussis cases for 2025 and 2026 to date.

If we focus on the two Januaries only (highlighted with pink arrows), because February isn’t complete yet, and compare the heights of the diagonally striped blue bars, there are five times as many cases in January 2025 as in January 2026. A big drop. After January 2025, there was a continued downward trend in monthly cases.

For your reference, January 2024 recorded only 833 cases.

So what?

The media story pushed our emotional fear buttons using scary language and poorly explained rising graphs while simultaneously underplaying the inherent variability that’s normal for pertussis. It does get some points for getting Dr Archana Koirala from NCIRS to acknowledge the infection pause resulting from the non-pharmaceutical interventions we used during the peak of our pandemic response.

Biology is complex, and microbiology and immunology certainly highlight that. Although writers try to keep things simple, things aren’t. When we underexplain topics like this and rely on fear to drive reads, we don’t help readers understand; we simply create more distractions and a freshly ploughed field for disinformation to grow. Well-pitched, clear and authentic communication could do a better job here.