Vaccination programs against whooping cough may not be fully effective because the bacteria that cause the disease have evolved new strains, a UNSW study has found.
A team of Australian scientists has shown for the first time that two of the most common strains of the Bordetella pertussis bacteria in Australia have undergone significant genetic changes since 1997, according to a report of the study published in the journal Emerging Infectious Diseases.
Those mutations coincided with changes to the type of vaccine used in Australia and with apparent increases in the number of cases of Australians contracting the highly contagious respiratory disease.
Before 1997, a "whole cell" vaccine was used. That was phased out over two years - due to concerns about side-effects - and since 1999 a new "acellular" vaccine has been used.
"A key issue is that the whole cell vaccine contained hundreds of antigens, which gave broad protection against many strains of pertussis," says one of the authors of the study, Associate Professor Ruiting Lan, of the UNSW School of Biotechnology and Biomolecular Sciences.
"But the acellular vaccine contains only three to five antigens. Our findings suggest that the use of the acellular vaccine may be one factor contributing to these genetic changes."
There has been growing concern among public health officials in recent years about the rising incidence of whooping cough, or pertussis, in Australia. Several significant outbreaks occurred last year in western Sydney, for example.
Lan's laboratory team - led by doctoral student Jacob Kurniawan - performed the genetic studies, working with researchers from the Centre for Infectious Diseases and Microbiology at Westmead and the University of Sydney, including Professor Peter Reeves.
Their findings suggest that while vaccination remains effective against some strains circulating in Australia it may no longer protect against two strains in particular, known as MT27 and MT70.
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