Pertussis adapts to boost its survival


Bordetella pertussis

Researchers say pertussis is becoming “smarter” as it evolves, and are calling for a new vaccine – but for now vaccination is vital, and pharmacists have a key role to play

Australia needs a new whooping cough vaccine to protect vulnerable people from the emergence of “superbug” strains, say researchers from the University of NSW.

The current vaccine, widely used since 2000, targets three antigens in the bacteria of the highly contagious respiratory disease which can be fatal to infants.

The researchers noted that all babies under six months old (especially newborns who are not protected by maternal immunisation) are at risk of infection as by this age they have not completed the primary vaccine course of three doses.

They say that a “whooping cough epidemic” from 2008 to 2012 saw more than 140,000 cases, peaking in 2011 with almost 40,000 cases, highlighted the rise of evolving strains of the disease which are able to evade vaccine-generated immunity.

In a series of UNSW studies, with the latest published in Vaccine, UNSW researchers took this knowledge further and showed, in a world-first discovery, that the evolving strains made additional changes to better survive in their host, regardless of that person’s vaccination status. They also identified new antigens as potential vaccine targets.

First author and microbiologist Dr Laurence Luu, who led the team of researchers with Professor Ruiting Lan, said whooping cough’s ability to adapt to vaccines and survival in humans might be the answer to its surprise resurgence despite Australia’s high vaccination rates.

“We found the whooping cough strains were evolving to improve their survival, regardless of whether a person was vaccinated or not, by producing more nutrient-binding and transport proteins, and fewer immunogenic proteins which are not targeted by the vaccine,” Dr Luu said.

“This allows whooping cough bacteria to more efficiently scavenge nutrients from the host during infection, as well as to evade the body’s natural immune system because the bacteria are making fewer proteins that our body recognises.

“Put simply, the bacteria that cause whooping cough are becoming better at hiding and better at feeding – they’re morphing into a superbug.”

Dr Luu said it was therefore possible for a vaccinated person to contract whooping cough bacteria without symptoms materialising.

“So, the bacteria might still colonise you and survive without causing the disease – you probably wouldn’t know you’ve been infected with the whooping cough bacteria because you don’t get the symptoms,” he said.

“Another issue with the vaccine is that immunity wanes quickly – so, we do need a new vaccine that can better protect against the evolving strains, stop the transmission of the disease and provide longer lasting immunity.”

While the researchers want to see a new vaccine developed and introduced in the next five to 10 years, Prof Lan said it was “critical” that for now, Australians get vaccinated with the current product.

“Although the number of whooping cough cases has increased during the past decade, it’s still nowhere near as high as what it was before the introduction of whooping cough vaccines,” Dr Luu said.

“Therefore, we emphasise that Australia must maintain its high vaccination coverage to protect vulnerable newborns who are not protected by maternal immunity and cannot complete the three-dose primary vaccine course until they are six months old.

“So, vaccination is especially important for children, people who are in contact with children and pregnant women who need the vaccine to produce antibodies to protect their newborns from developing whooping cough in the first few weeks of life.”

Older people, people who live with somebody who contracts whooping cough, and anybody who has not had a booster in the last 10 years are most at risk, Prof Lan said.

Anthony Tassone, Victorian branch president of the Pharmacy Guild, told the AJP that it was very concerning to hear of the potential resistance to the whooping cough vaccine of the causative bacteria.

“In the meantime, vaccination with the current vaccine is still our best protection against this potentially deadly infection,” Mr Tassone said.

“Community pharmacy has a significant role to play in helping achieve ‘herd immunity’ with trained pharmacist immunisers authorised to administer the whooping cough vaccine in every state and territory in Australia, with some jurisdictions including: Victoria, Western Australia and Tasmania allow administration to patients from 16 years of age. 

“Herd immunity is a team effort – all trained immunisers across the health professional workforce have a role to play and we need to give patients as many opportunities to safely access receiving vaccination services.”

Mr Tassone also expressed disappointment that a number of celebrities have recently been campaigning against vaccination.

“It is infuriating to hear of some celebrities continuing to publicly espouse their ill-informed ‘anti-vaxxer’ views that are just plain dangerous,” he said.

“Rather than the term ‘anti-vaxxer’ I feel terms such as ‘pro-plague’ or ‘pro-death’ would be far more appropriate given the potentially devastating consequences of some of these preventable diseases – such as what was seen with the recent measles outbreak in Samoa.”

Recent examples include influencer Taylor Winterstein, who is married to rugby league player Frank Winterstein, and who has been campaigning against compulsory vaccination in Samoa, saying vaccination is the cause of the outbreak.

As at 7 January, the death toll from the measles outbreak in that country stood at 83.

Celebrity chef Pete Evans also drew criticism this week after he promoted the work of prominent anti-vaccination campaigner Robert F Kennedy Jr, saying the work was “important”.

These comments drew the ire of the RACGP, with national president Dr Harry Nespolon telling newsGP that the anti-vaccination movement is “intensely frustrating” and undermining some of the gains made by vaccines in improving public health.

“Pete Evans should stick to talking about ‘activated almonds’ and leave vaccinations alone,” Dr Nespolon said.

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