Have you treated anyone for influenza yet this season? The flu is just beginning to rear it’s ugly head. Body aches, fevers and coughs are making their way across the country. Unfortunately, we may have little help fighting influenza this season as even in the early days of flu season it looks like this year’s vaccine will be largely ineffective.
Yesterday I had the chance to chat with Gerri Willis, host of Fox Business’ The Willis Report, about the 2014-2015 influenza season and the level of protection we can expect from this year’s flu vaccine. In the segment I addressed this year’s flu strain and answered questions about the influenza vaccine. Here’s what your patients will be asking in the coming months:
Q: What’s the latest on this year’s flu shot? Is it working?
A: Unfortunately, it looks like this year’s flu shot it not a good match for the strain of influenza that is currently circulating. The flu shot protects against three or four strains of the flu, two strains of influenza A and one or two strains of influenza B, depending on which vaccine you receive.
The strain of influenza currently making it’s way across the country is H3N2, an influenza A virus. Although the 2014-2015 influenza vaccine does protect against H3N2, the particular type of H3N2 we are now seeing has mutated. This means that even if you have been vaccinated, your immune system cannot recognize this particular form of the H3N2 virus so the flu shot does not protect against it.
Q: Why isn’t this year’s flu shot working?
A: Each year in February, a panel of experts decides on the three or four strains of influenza to include in the coming season’s flu vaccine. This decision is made based on the common strains circulating around the globe throughout the year. These experts must predict which flu strains will be most prevalent in the coming season.
Some years experts predict what strains of flu will be present more accurately than others. This year, although experts did predict that the H3N2 strain would circulate, the H3N2 virus has mutated and looks differently than anticipated. This means the flu vaccine is not a good match for the virus.
Q: How does the influenza virus mutate?
A: The flu virus can mutate in two different ways. Sudden changes in the virus occur by a process called “antigenic shift”. Gradual changes occur through a process called “antigenic drift”. This year, we are seeing the H3N2 strain of influenza mutate via “drift”.
“Drift” occurs as a virus replicates and small changes in it’s genetic material occur gradually over time. Even though genes in the virus are changing, these changes are usually small. Your immune system can still recognize the flu virus and respond to it if you have been vaccinated.
Eventually, over time these small genetic changes accumulate and make the virus look different enough that is is no longer recognized in the same way by the body. When this happens, you may become sick as a result of the influenza virus even if you have had the flu vaccine. This is the case with this year’s H3N2 strain.
Q: Is this year’s flu season expected to be worse than usual given the inefficacy of the influenza vaccine?
A: In short, yes. This year’s flu season could be particularly bad. In 52% of cases of the H3N2 strain of influenza, the flu shot has been shown to be ineffective. This coupled with the fact that H3N2 is a particularly nasty strain of flu is setting the stage for a rough season. In past years where H3N2 was the predominant strain of influenza, hospitalizations and deaths from the flu doubled in at risk populations such as young children and the elderly.
Q: If I get sick I can just take Tamiflu, right?
A: In a technical sense, antiviral medications like Tamiflu and Relenza are effective against this year’s circulating flu strain. The H3N2 stain of flu shows 100% susceptibility to these medications.
Unfortunately, this 100% susceptibility doesn’t amount to much in a practical sense. Antiviral medications must be started within 48 hours of the onset of illness for full efficacy and many people miss this window in seeking medical attention. And, even though antivirals do help stop the flu virus from replicating inside the body they only reduce the course of illness by about half a day. In children, some studies show these medications may even increase the severity of some symptoms like nausea and vomiting.
Antiviral medications certainly aren’t miracle drugs when it comes to treating influenza and their value has been called into question. Your best bet this flu season? Practice prevention.
Q: Should I still get a flu shot?
A: Yes! Although this year’s flu vaccine isn’t great, it can still help. If you fall ill with the mutated strain of H3N2, there is still some cross-reactivity with the type of H3N2 included in the flu shot. Your symptoms may be less severe and your course of illness shorter if you have been vaccinated.
Even though the flu shot is not very protective against the currently circulating influenza strain, this could change later in the season. Last year, for example, we saw a spring flu of a different strain late in flu season. We can’t predict what will happen in the coming months.