Australia was among the countries hit by sharp whooping cough rebound as post-pandemic susceptibility rose.
Australia experienced a sharp resurgence in pertussis following the covid pandemic, mirroring trends seen across Europe, North America and parts of Asia, according to new international surveillance data.
After historically low notifications during the pandemic, Australia recorded a steep increase in cases in 2024, with the highest burden concentrated in school-aged children.
Researchers have warned that the rebound underscores both the vulnerability created by waning population immunity and the continued need to strengthen maternal and childhood vaccination strategies.
The global findings, originally presented at an online workshop organised by the International Bordetella Society in late 2024, have been published this month in JAMA Network Open.
Pertussis surveillance data from Australia, Japan, China, South Africa, the US and several European and Latin American countries were presented at the workshop.
Variations in incidence, alongside differences in vaccination schedules, diagnostics, and surveillance systems, were noted in these countries, but most countries reported a marked resurgence of pertussis following the covid pandemic to levels that exceeded those seen in recent peak years.
“The potential for large outbreaks of pertussis highlights the importance of maintaining or increasing vaccine coverage in pregnancy and in infants and children,” the researchers wrote.
“The data presented herein suggest a need for new pertussis vaccines that protect against both disease and infection and that reduce transmission.”
Pertussis activity in Australia remained suppressed for several years under pandemic mitigation measures, but circulation re-established later than in the Northern Hemisphere.
National data showed a significant rise in 2024, with incidence in children aged 5-14 years reaching 1003 per 100 000 – the highest rate across all participating countries. Elevated rates were also seen in children aged 1-4 years at 409 per 100 000.
In contrast, the proportion of cases occurring in infants under 12 months remained stable compared with 2019, suggesting maternal and early infant vaccination continued to provide meaningful protection against severe disease.
According to Australia’s National Notifiable Disease Surveillance System (accessed 3 December), there were 57,254 cases of pertussis in total in 2024, compared to 2452 in 2023, 484 in 2022, 550 in 2021, and 3460 in 2020.
So far this year in Australia there have been 23,970 cases of pertussis reported to the NNDSS.
Australia has historically reported one of the largest proportions of pertactin-negative Bordetella pertussis strains globally, approaching 100% before the pandemic.
Workshop data indicate that this figure has since decreased to around 60%, aligning with trends seen in other high-income countries where pertactin-expressing isolates have re-emerged.
Several macrolide-resistant isolates were also identified in Australian samples. Although resistance remains uncommon, the international increase – particularly the dominant macrolide-resistant ptxP3 lineage circulating widely in China – has heightened concern about treatment delays in infants and the reduced effectiveness of prophylaxis for close contacts.
The resurgence is consistent with the global pattern observed in 2023-2024.
Most countries reported minimal transmission during covid and an abrupt surge after public-health restrictions lifted. Adolescents and school-aged children accounted for a substantially higher proportion of cases compared with pre-pandemic years, a shift seen in Australia, France, England, Finland and Czechia.
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Researchers attribute this to waning vaccine-induced protection combined with the loss of natural immune boosting that usually occurs through periodic asymptomatic infection.
Diagnostic practices evolved during the pandemic, particularly the adoption of multiplex PCR, but the researchers noted that testing changes alone could not explain the scale of the increase.
For Australia, the data strengthens the case for maintaining high uptake of maternal vaccination and timely completion of the childhood schedule, which includes acellular pertussis doses at two, four and six months, followed by boosters at 18 months, four years and 12–13 years.
Given the disproportionate rise in cases among older children, the findings also raise questions about the durability of immunity conferred by multiple acellular boosters.
Specialists at the workshop emphasised that while current vaccines were effective in preventing severe disease in infants, they had limited impact on transmission.
“The data on resurgence of pertussis presented herein and in other published studies highlight the importance of maintaining or increasing vaccination coverage during this period of high pertussis incidence after the Covid-19 pandemic, in particular to protect infants both by vaccines given during pregnancy and in the primary schedule,” they wrote.
“These data also confirm the need for new pertussis vaccines that protect against both disease and infection and thus reduce transmission.”
