Researchers at the University of New South Wales (UNSW) said on Tuesday that Bordetella pertussis, the virus that causes whooping cough, has changed in Australia, which may reduce the effect of vaccines.
Strains of the virus from across Australia were analyzed. Researchers found that a key surface protein called pertactin was no longer being produced. Approximately 80 percent of whooping cough cases in 2012 were caused by pertactin-free strains.
"It's like a game of hide and seek," Ruiting Lan, the UNSW associate professor in the School of Biotechnology and Biomolecular Sciences, said. "It is harder for the antibodies made by the body's immune system in response to vaccination to 'search and destroy' the whooping cough bacteria which lack pertactin."
Lan said the results suggest pertactin-free strains have gained an advantage over strains with pertactin. Pertactin-free strains have been discovered in France and the United States as well.
Approximately 142,000 cases of whooping cough were studied between 2008 and 2012.
Lan said more studies are needed to better understand the effect of vaccination on the organism's evolution. The current vaccine was created in 1997 to replace a previous version.
"Vaccination is still the only way to protect against whooping cough, especially for the youngest babies who are most at risk of severe illness," Lan said.