Current article on whooping cough vaccine

Why whooping cough’s making a comeback

Wendy Zukerman, Asia Pacific reporter

Whooping cough is on the rise in industrialised countries, despite long-standing vaccination programmes. Now researchers from the University of New South Wales in Sydney, Australia, have an explanation for why: at least two strains of the bacteria that cause the infection have evolved to evade today’s vaccines.

According to The Daily Telegraph of Sydney, “the research team analysed more than 200 samples of the bacterium collected over the past 40 years in Australia and compared them with samples from Japan, Canada, USA and Finland”. They found that there are at least two strains that the vaccine may not protect against – known as MT27 and MT70.

At least in rich countries, many people may think that whooping cough – also known as pertussis – is a killer from a pre-vaccination era. The new study, which is published in this month’s edition of the journal Emerging Infectious Diseases, emphasises that incidence rates have been recently increasing in many industrialised countries. Prior to this study, scientists were unsure why.

Now it seems an upgrade to a new type of vaccine may be to blame. Up until 1997, a “whole-cell” vaccine was used before it was phased out over two years because of concerns about side effects. Since 1999, a new “acellular” vaccine has been used. One of the authors of the study, Ruiting Lan, told The Advertiser of Adelaide, South Australia:

“A key issue is that the whole-cell vaccine contained hundreds of antigens, which gave broad protection against many strains of pertussis. 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.”

To confirm their suspicions, the researchers also analysed particular genes in the bacteria’s DNA that make the three to five antigens which interact with the new vaccine. “The new strains have a new copy of the gene and so will make a slightly different antigen,” said Lan, which means the mutated strains are unlikely to react to an immune response arising from the vaccine.

According to Pharmacy News of Australia, Lan is warning that vaccination is still very important because it offers protection from many strains

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