More study is needed to tell whether the new strain is more likely to kill patients and whether the current vaccine can protect against it completely, said Ian Barr of the World Health Organisation Collaborating Centre for Reference and Research on Influenza in Melbourne, Australia and colleagues."However, it may represent the start of more dramatic antigenic drift of the pandemic influenza A(H1N1) viruses that may require a vaccine update sooner than might have been expected," they wrote in the online publication Eurosurveillance.
It is possible it is both more deadly and also able to infect people who have been vaccinated, they said.
Flu viruses mutate constantly -- this is why people need a fresh flu vaccine every year. Since it broke out in March 2009 and spread globally, the H1N1 swine flu virus has been very stable with almost no mutation.
"The virus has changed little since it emerged in 2009, however, in this report we describe several genetically distinct changes in the pandemic H1N1 influenza virus," Barr's team wrote in the report, available at http://www.eurosurveillance.org/ViewArticle.aspx?ArticleId=19692.
"These variants were first detected in Singapore in early 2010 and have subsequently spread through Australia and New Zealand."
The changes are not significant yet, they said. But there have been some cases of people who were vaccinated also becoming infected, and also some deaths.
"Already this variant virus has been associated with several vaccine breakthroughs in teenagers and adults vaccinated in 2010 with monovalent pandemic influenza vaccine (protecting against only H1N1) as well as a number of fatal cases from whom the variant virus was isolated," they wrote.
But there is not enough information to tell whether there may have been other factors making the patients more vulnerable, they stressed...
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