“Mutated Flu Strain…”

“Early data suggests potentially severe flu season…”

“The flu vaccine isn’t effective…”

I have seen all of these headlines in various forms from news outlets and social media in the last week. So what does all of this really mean? Let’s break this one down to the scientific level…

Viruses can be quite tricky little characters, and one thing they do very well is mutate as they replicate. There are two types of changes that can occur in the structure of a virus. First, there is drift which means that the structure of the virus changes ever so slightly, but the majority of the virus remains the same. These changes can accumulate overtime and eventually lead to the virus looking different than it did before. This is what occurs with the common cold and stomach viruses which is why you can get these several times a year let alone over your lifetime. Think of drift as a changing of accessories. If you just change earrings, you might not look so different to others, but if you “drift” from your usual look and put your hair in a ponytail and add a hat with sunglasses, people might not recognize you right away.

“Think of virus shifting like someone getting a drastic face lift…they look nothing like they did before.”

Then there is shift. This occurs when the entire structure of the virus down to its core proteins changes, and these changes often happen abruptly. When shifting occurs, the virus becomes completely unrecognizable to the body’s immune system. This is what occurred with the H1N1 swine flu pandemic in 2009. Think of virus shifting like someone getting a drastic face lift…they look nothing like they did before.

So that brings us to this year and the flu strains that are being seen. So far, of the flu cases that have undergone special genetic testing, about 58% of the cases of influenza A are being caused by a “drift variant” of the H3N2 strain of flu which is not included in the vaccine. The other 42% of cases of influenza A are being caused by strains of the virus that are included in the vaccine. The few strains of influenza B, which is accounting for only about 10% of overall flu activity, are covered in the quadravalent flu vaccine.

“Since the flu virus is ever changing, drifting, and shifting, this is like predicting hurricanes months in advance or who will play for the college football championship 6 months before college football even starts!”

Some may ask “Why isn’t the flu vaccine created when we know what strains of the flu will be circulating?” Since it takes many months to manufacture the flu vaccine, the decision on what specific strains of the virus to include in the vaccine is made approximately 6 months prior to the start of flu season (which usually means in about February for the following flu season). Through scientific study of prior flu seasons, scientist attempt to predict what strains of flu we will see the following season and then base the vaccine on those predictions. Since the flu virus is ever changing, drifting, and shifting, this is like predicting hurricanes months in advance or who will play for the college football championship 6 months before college football even starts! Sometime the predictions are correct and sometimes they are not even in the right conference by the time the games are played!

This year, the drift variant H3N2 strain was the hiccup in the prediction model. While the flu vaccine does not specifically contain protection against this strain of the virus, it does protect against other strains of both flu A, including the “typical” H3N2 strain, and flu B types. Scientists believe that while the vaccine may not give great protection from getting the variant H3N2 strain, it may lessen the severity of the flu if you get this particular strain because of cross-protection.

In the end I think it is still very important to get your flu vaccine this year. Protection from 4 strains of flu virus is certainly better than no protection at all.

*A quick word of warning about H3N2 strains in general…historically, these strains have caused more severe illness that can result in hospitalization or even death, which becomes especially important for the very young, anyone with underlying medical conditions (ex: lung problems, heart conditions, etc), or the elderly. H3N2 viruses were most common during the 2012-2013 flu season which brought the highest number of pediatrics deaths attributed to flu within the past decade. As I mentioned in my prior post, there have already been 5 pediatric deaths this flu season! Four of these children died from one of the influenza A strains (did not subtype to know if the variant H3N2 strain was the culprit) and one death was attributed to influenza B. So if you or your child begin showing flu-like symptoms, see your doctor sooner rather than later as the discussion about the use of anti-viral medications will be very important this year.

For the latest information on flu activity in the US, click here.