Public health experts are warning that the upcoming flu season may a rough one in this country, as data from Australia indicate the vaccine selected for this year’s strain isn’t effective against the virus.

The flu vaccine used this year in Australia — which has the same composition as the vaccine used in the U.S. — was only 10 percent effective, according to a preliminary estimate, at preventing the strain of the virus that predominantly circulated during the country’s flu season,an international team of medical experts wrote in a perspective published today in The New England Journal of Medicine.

“However imperfect, though, current influenza vaccines remain a valuable public health tool, and it is always better to get vaccinated than not to get vaccinated,” the team emphasized.

In the The New England Journal of Medicine report, the authors indicate that vaccines may fail to protect against this year strains of the influenza A (H3N2) virus.

“Given that most of the U.S. influenza-vaccine supply is currently produced in eggs and the composition of the 2017-2018 Northern Hemisphere vaccine is identical to that used in Australia, it is possible that we will experience low vaccine effectiveness against influenza A viruses,” Fauci, his Australian counterpart, and two World Health Organization officials wrote.

H3N2 was the most predominant flu strain among Australians and unfortunately, the vaccine did little to protect them. According to preliminary estimates, the vaccine was only 10 percent effective.

This year’s virus, H3N2 Flu, is actually a subtype of influenza A. While there are multiple types of influenza, only influenza A is further broken down into subtypes.

Although flu symptoms are typically similar no matter the strain of influenza, history has shown that seasons in which H3N2 influenza A is the dominant strain have been more severe.

From 2003 to 2013, the three flu seasons that were dominated by H3N2 strains of the flu had the highest mortality rates – causing more deaths on average than other years (excluding the 2009 H1N1 pandemic flu).

At the beginning of the 2014-2015 flu season, a mutated version of H3N2 has caused a majority of the flu in the United States.

The mutated virus was different from the strain of H3N2 influenza A that was included in that season’s vaccine. Unfortunately that means the vaccine did not provide as much protection against the flu as it would have otherwise. However, that doesn’t mean it doesn’t work at all.

Why is it that the flu viruses can mutate but still pose significant health effects?

The answer has to do with how influenza distracts your immune system. Flu viruses are studded with a protein called hemagglutinin. It helps the virus attach to the cells in your airway and fuse with them. It’s also cloaked in tiny loops that catch the immune system’s attention.

It’s like having a lightning pole. You sort of spend a lot of your immune reaction on these loops,” [says James Crowe, director of the Vanderbilt Vaccine Center at the Vanderbilt University Medical Center]. “The flu tricks you into focusing on areas that are not as important.” These loops can change endlessly, he says. And because they aren’t critical for the virus’s survival, they can mutate a lot without harming it.

All of this means flu viruses can change just enough that the immunity you had from your last vaccine will be a little bit off and won’t work so well anymore. “Those are minor changes, but they require us to refresh the vaccines every year,” Crowe says.

Here’s to hoping our Legal Insurrection readers stay healthy during this year’s flu season.