Is this year's flu vaccine effective?

January 10, 2013 7:07 AM

I keep reading stories (1, 2, and this previous question) about how bad this year's flu season is. It's been a few months since the vaccine has been available so have they been able to determine if this year's vaccine matches up with the flu strains that are spreading? Meaning, is this year's flu vaccine actually effective? When is that determination made?

I'm planning to get the flu shot but since it's already so late, I was wondering if data about its effectiveness was available.

posted by exhilaration to Health & Fitness (25 answers total)

This year's flu shot immunizes against 3 strains. Two A's and a B, IIRC. Next year's will be 2 A's and 2 B's.

They can't immunize for everything, but they do the best to get the biggest threats. Getting a flu shot won't hurt you, you know you'll be protected against at least 3 strains. Sure there may be rogue strains going around, and you may still get sick, but you've reduced your chances by 3.
posted by Ruthless Bunny at 7:11 AM on January 10, 2013

Three things.

First, the decision about which flu strains to include in each year's vaccine is made months before it's released to the public. It takes that long to grow and prepare that amount of virii. So it's a guess, really, about which strain(s) will be dominant. Sometimes they get it right. Sometimes, like this year, they don't.

Second, the "flu virus" is actually a collection of distinguishable virii, all of which mutate rapidly. That's why annual vaccination is important. Not only does immunity to virus A not necessarily grant immunity to virus B, but virus A may and probably will mutate such that your immunity is obsolete in a few years or even months.

But third, it's believed that a sustained pattern of annual flu vaccinations has a sort of cumulative effect. It's as if by giving the body a regular change to exercise against the flu, in a variety of changing forms, it gains the ability to fight all flu virii more effectively. This isn't necessarily immunity, but there is evidence to suggest that the severity of flu infections is lesser in people that have been vaccinated repeatedly over several years, even given the multiplicity and rapid mutation of virii.

So go ahead and get vaccinated. It won't do you any harm, and it might well do you--and everyone around you--some good.
posted by valkyryn at 7:13 AM on January 10, 2013 [9 favorites]

I have heard that this year's vaccine is a good match for the flu that is going around. I wish I could remember where I heard it, so I could give you a source, but I can't. All I know is when I heard that, I decided I would go ahead and get the vaccine this year.
posted by cooker girl at 7:13 AM on January 10, 2013

The wikipedia article on the flu vaccine effectiveness has a few good links if you want to read some studies and meta-analysis.

Be aware that if you just google "flu vaccine effectiveness" you'll get a lot of sensationalistic newpaper stories and anti-vax'ers without any actual scientific data.
posted by blue_beetle at 7:14 AM on January 10, 2013 [4 favorites]

The recent study I saw showed a 59% rate of immunity. This ignores herd immunity (people who get the shot thus lowering the chances of people who didn't get the shot from getting the flu because they won't be the ones spreading it.) For those who end up getting the flu, assuming its one of those strains, the effects should be a lot more mild. Of course no vaccination is perfect, but it beats nothing.

Also, is it really too late for the shot? I think its mostly effective in as little as 2 weeks and fully effective in 4. You might want to call your doctor and ask, but I'm really skeptical that Jan 10th is too late unless you live in an especially warm climate. I've seen people get sick as late as April or even May, but then again I live in the midwest. I say go ahead and get it.
posted by damn dirty ape at 7:19 AM on January 10, 2013

Oh and just to clarify, 59% isn't necessarily bad. I think historically we're looking at around 65-70% efficient. The various flu strains means we'll never have 90+ percent like other vaccines.
posted by damn dirty ape at 7:24 AM on January 10, 2013 [2 favorites]

Response by poster: I don't buy into the anti-vaxer stuff and I don't think it's too late at all to get the shot, I'm just curious about its actual effectiveness this year. Since the flu is getting so much attention this year I would think they should be able to figure if the strains that are spreading in the wild match up to the vaccine.
posted by exhilaration at 7:26 AM on January 10, 2013

Best answer: The CDC weekly flu report has more information about this than you'll know what to do with.

Specifically:
-All (17) of the 2009 H1N1 categorized since October matched the strain used in this year's vaccine.
-279 out of 281 of the H3N2 viruses tested matched the strain used in the vaccine.
-79 out of 115 influenza B viruses tested matched the strain used in the vaccine.

Now this is just for the ones that they've antigenically characterized, but it shows a trend. The H3N2 version is the one that's most common in the US right now. And the flu shot vaccinates against the strain that accounts for 99.3% that they've tested.

So yes. Even though I am someone who got the flu shot and then caught a flu or flu-like bug a month later, I would recommend that you get the shot.
posted by specialagentwebb at 7:27 AM on January 10, 2013 [12 favorites]

Best answer: From the CDC FluView weekly summary -

• All 17 of the 2009 influenza A (H1N1) viruses were characterized as A/California/7/2009-like. This is the influenza A (H1N1) component of the Northern Hemisphere vaccine for the 2012-2013 season.
• Of the 281 influenza A (H3N2) viruses, 279 (99%) were characterized as A/Victoria/361/2011-like. This is the influenza A (H3N2) component of the Northern Hemisphere influenza vaccine for the 2012-2013 season.
• Approximately 69% of the 115 influenza B viruses belonged to the B/Yamagata lineage of viruses, and were characterized as B/Wisconsin/1/2010-like, the influenza B component for the 2012-2013 Northern Hemisphere influenza vaccine. The remaining 31% of the tested influenza B viruses belonged to the B/Victoria lineage of viruses.

Sounds good to me!
posted by mskyle at 7:28 AM on January 10, 2013 [1 favorite]

Some food for thought:
Can You Get A Flu Shot And Still Get The Flu? (NPR)

What You Should Know for the 2012-2013 Influenza Season (CDC)
(Part of the above linked)
How effective is the flu vaccine? (CDC)
Will this season's vaccine be a good match for circulating viruses? (CDC)

Anecdata: my whole office is sick, but I got the flu shot this year and I'm fine.
I've heard on the news that this year's flu shot is "a very good match" for the most prevalent strain of flu.
I had two different types of hellflu last year (one that transitioned into bronchitis), and didn't get the flu shot.

I'd get the flu shot. Like valkyryn says, the potential positives and positive externalities outweigh the negatives.
posted by xiaolongbao at 7:30 AM on January 10, 2013 [1 favorite]

We have vaccines given at work and one of my colleagues doesn't have them as he got flu-like symptoms as a result (non-scientist's interpretation - there's a bit of flu in the vaccine in order to build up resistance). So there's that.

All vulnerable groups in Britain such as the elderly and pregnant are encouraged to get the flu vaccine, and it seems unlikely that it would be given en masse if it was not considered to be sufficiently protective.
posted by mippy at 7:36 AM on January 10, 2013

I heard a report that it has 60% efficacy. Which to me says 'it might work, it might not' which is about like 'you might catch the flu in the first place, you might not'. Which I know is horribly faulty logic and not what those numbers mean, but still.
posted by greta simone at 7:36 AM on January 10, 2013

Mod note: Folks, please answer the question being asked. This is not a larger discussion of vaccination politics or economics
posted by jessamyn (staff) at 7:51 AM on January 10, 2013

Obviously this will vary from person to person. But for some anecdata, I got the flu shot at my doctor's office in September. I had never had the shot before. About six weeks ago, I had a cold that lasted less than a week and was annoying for a few days but not a big deal.

My husband has not gotten the flu shot. He got sick a few days after I did. He was in bed for 5-6 days and was generally unhappy for at least two weeks.

I'm not a flu vaccine evangelist but I'm inclined to get another one next year.
posted by kat518 at 7:56 AM on January 10, 2013 [1 favorite]

I've heard that same thing from nurses: "the shot doesn't protect against the one that's going around." But the evidence here shows that it does. I'll believe actual testing from the CDC over gossip from nurses.
posted by gjc at 8:16 AM on January 10, 2013 [4 favorites]

A major reason for the high number of flu infections is the vaccination rate; this CDC page suggests it was 36.5% as of November. Unfortunately the erroneous information that is out there helps keep the vaccination rate lower than it should be.
posted by TedW at 8:29 AM on January 10, 2013 [6 favorites]

Well if you're interested in anecdotes I got the flu vaccines and have not gotten sick. Knock on wood.
posted by dfriedman at 8:44 AM on January 10, 2013

Even if the strain you get is not a match for one in the vaccine, the vaccine can still provide some protection. My doctor says that it may not prevent you from getting sick from unmatched strains, but it may decrease the severity. From the CDC:

Can the Vaccine Provide Protection Even if the Vaccine is Not a "Good" Match?
Yes, antibodies made in response to vaccination with one flu virus can sometimes provide protection against different but related viruses. A less than ideal match may result in reduced vaccine effectiveness against the virus that is different from what is in the vaccine, but it can still provide some protection against influenza illness.
In addition, it's important to remember that the flu vaccine contains three virus viruses so that even when there is a less than ideal match or lower effectiveness against one virus, the vaccine may protect against the other viruses.
posted by bluefly at 8:49 AM on January 10, 2013

Getting a flu shot also protects the people you might've exposed to the flu, some of whom are immune-fragile. And you build up your own immune system with flu antibodies.
posted by theora55 at 8:54 AM on January 10, 2013

Anecdata again. I got the shot - I get it every year. I am fine, though last year I got a bad flu despite getting the shot. However, this year my live-in partner, who did not get the shot, was laid low by an 8-day full-on flu attack, while I was AOK throughout and still am. So I feel the vaccine gave me some protection this year, though I got something it didn't impact last year.
posted by Miko at 9:47 AM on January 10, 2013 [1 favorite]

I got the shot and have been in close proximity with at least 7 people who got the flu since NYE (and was at a NYE party that resulted in at least 4 people catching the flu) and I'm amazingly still holding strong (I keep getting paranoid every time I feel tired or sneeze...). Yet another person at work came down with a really bad case of the flu yesterday who I had been sitting across from in a meeting on Tuesday as she sneezed away, but I appear to be fine. So yeah if anyone hasn't gotten it I would be running to your nearest drug store. I had a friend who passed out and had to get some kind of crazy shots for it. Not pleasant.
posted by whoaali at 11:26 AM on January 10, 2013

The Diane Rehm show was about this today.
posted by empath at 11:29 AM on January 10, 2013

I got the shot in the Fall and still got the flu around Christmas. This was proper influenza, ie cough, difficulty breathing, fever, aching, loss of appetite, and no runny nose, no sneezing.

However, I'm only one data point. The vaccine isn't claimed to be 100% effective against all strains.
posted by w0mbat at 11:46 AM on January 10, 2013

Best answer: It doesn't seem like anecdotes are what the OP is asking for, nor what the questions calls for.

It's been a few months since the vaccine has been available so have they been able to determine if this year's vaccine matches up with the flu strains that are spreading? Meaning, is this year's flu vaccine actually effective? When is that determination made?

Yes, they have. This year's flu vaccine is fairly but not completely effective. Even in the cases where it does not completely protect against the flu it can lessen severity. The determination as to how closely this year's prominent flu strains match those in the vaccine is made during flu seasons as laboratory confirmed cases of influenza are typed and compared to those in the vaccine.

The data shows that this year's major flu in the USA is well matched but that the vaccine itself is very slightly less protective than usual, though still quite effective. I don't know why that is. Maybe a simple function of the severity of this year's strain? Still, given that H3N2 is very common in the USA this year and often causes severe illness, even incomplete protection which lessens severity is very important.

The vaccine is available for free in many places so there is no excuse short of allergy or past history of guillain barre and the like for not getting vaccinated this year and every year.
posted by Justinian at 12:05 PM on January 10, 2013

Today's MMWR from the CDC: Early Estimates of Seasonal Influenza Vaccine Effectiveness — United States, January 2013


"After adjustment for study site, but not for other factors, the estimated vaccine effectiveness (VE) was 62% (95% confidence intervals [CIs] = 51%–71%). This interim estimate indicates moderate effectiveness, and is similar to a summary VE estimate from a meta-analysis of randomized controlled clinical trial data (2); final estimates likely will differ slightly."
posted by gingerbeer at 9:54 AM on January 11, 2013 [1 favorite]