Something I have wondered about, but can’t find anything that addresses it. So they put three or four common strains of the virus in each year’s batch based on prevalent strains and best guess.
It’s pretty widely reported now that the prediction wasn’t very good this year, and the virus mutated into versions that the vaccine didn’t prepare immune systems for very well.
The thing I haven’t seen covered is how much good previous year’s vaccine does. In this specific case and in general. If person A has been getting the flu vaccine every year for ten years, and person B got their first ever shot this year, does A have a measurable advantage in avoiding the flu that given year? Do the common flu viruses mutate so fast and so completely that no antibodies more than 12 months old are any good, or do you start to build up a spectrum of flu immunities over the years that help you.
(1) As you get varying flu shots every year, “do you start to build up a spectrum of flu immunities over the years” (OP’s wording) that covers a bunch of different strains that you might encounter in the future? Or is each year’s new strain SO different that prior years’ vaccines don’t count?
But also:
(2) How long do those various immunities persist anyway? On this, ISTM I’ve seen it mentioned in some article somewhere: Not very long. Unlike some other immunities that are long-lasting (e.g., the tetanus shot that needs a boosted every 10 years; or the Sabin polio vaccine that was supposedly life-long), the impression was that the annual flu immunity fades relatively quickly. To whatever extent that is true (if at all?), I gather that your past history if flu shots doesn’t help you much in the long run.
ETA: Okay, now that I’ve spouted off with some vague uncited recollection, I’m starting to do some actual googling: how long does flu immunity last. My immediate result is: Lots of hits. I’ll come back when I’ve found something particularly helpful-looking.
Okay, here’s one cite: Article in TIME Magazine, Aug. 26, 2008, discussing one researcher’s findings that looked at still-living survivors of the 1918 flu epidemic, and found that their antibodies to that flu are still strong.
ETA: As I’m skimming through the various top hits from that google search, one thing I’m noticing (not too surprisingly) is that most of the discussions DON’T distinguish much between the two separate questions. Most of the seem to ask the question “Does the flu vaccine last very long?” but then focus more on answering the other questions instead, that the doesn’t work well from year-to-year because of the changing strains.
As I’m skimming some cites, I’m seeing a common pattern showing up: A lot of them are saying something to the effect: The flu vaccine immunity is long-lasting, where “long-lasting” seems to be defined as “one year, long enough to get you through one flu season”.
Uh, thanks. That’s not the kind of long-lasting, y’know, long-lasting that the OP (and I) are probably looking for.
They are actually very difficult questions to answer because it really depends on who is being vaccinated and with what and how protected is being defined.
The elderly for example have less strong of responses to the vaccines and it fades faster.
The live weakened nasal vaccine has in the past provided more protection from antigenic drift (we’ll se how it did this year) and should theoretically produce more lasting immunity as it induces both the antibody response (easy to measure) and the longer lasting but harder measure cellular immune response. And natural disease produces some longer lasting protection to the particular strain for the same reason. The injectable only does the antibody side of the protection spectrum (which again, fades faster, probably by a year).
The nasal though works better in kids than in adults (although it still works in adults fine enough) precisely because kids are less likely to already be immune. The virus needs to replicate in the nasal mucosa some to induce the response and being immune already may reduce how well it can do that. Still it does seem to work year on year in kids so go figure.
To summarize:
The injectable flu vaccine probably does not help one build up a spectrum of antibodies. The antibody levels probably fade to below protective levels by a year or two out and on the early side for the elderly. Not so much because the virus changes each year but a drifted one won’t be much protected all by previous years’ shots.
Not sure well the antibody type protection (humoral) for influenza seems to fade so relatively quickly. Again the nasal vaccine’s induction of some cellular protective response should be longer lasting but I don’t know how long it has been followed out.
I really wouldn’t have a personal problem with multiple flu vaccinations every year if it would have any effect on preventing or reducing the severity of flu. I’d seek it out. The downside to a flu vaccination is a slight needle prick, a much smaller needle than 40 years ago, a sore arm and a slow day or two. It is, overall, a very safe vaccination and the more people who get them, the number of people suffering is vastly reduced.
Wasn’t this year’s vaccine (2014-2015) exactly the same as last year’s vaccine (2013-2014)? I thought that’s why it was available in August this year, instead of October; they had a head start making it. That would support the notion that they don’t expect the immunity to last beyond a year, as we weren’t told we could skip it this year if we got it last year. (Or the notion that the CDC really are evil bastards raking money in hand over fist by giving out bad medical advice, but as that’s an antivax position, I’m disinclined to believe it.)
I think the fact is that no one really knows how much protection with the injectable lasts from season to season. The reason Senegoid’s link was talking long lasting as lasting through out the season was the belief that some held for a long time that if one (especially an older one) got vaccinated “too soon” in the season it might be warn off with a flu peak in later January or February. That turns out to be clearly not the case.
Trying to find information on protection lasting between seasons is not so easy … I did find this though, published a year ago.
Summarizing what they found was that the next season vaccine efficacy was at 80% for one component (pandemic H1N1 A); 51% for H3N2 A and for B. 80% is pretty good but 51% is not generally considered good enough.
And digging a bit more also this published just a few months ago that directly addresses the op:
Such is the current state of the art. Still fuzzy and of course more research is needed. As always. FWIW.
Since it’s GQ I’m waking up my thread since I came across some relevant study, in case anybody else was still interested.
Looks like a study was recently done that shows repeated vaccinations is providing greater flu immunity and resistance to severe symptoms. It’s just a national news report so details are a big non-speciifc but it sounds like a broader spectrum is creating by the body’s immune system
ETA, at least for over 65ers which was the only population in the study.
A reminder that while preliminary reports suggested this year’s flu vaccine was only “10%” effective, that apparently was based on reports from Australia.
In the southern winter in Australia, we had the worst flu season in decades. I was vaccinated. And got the flu. In America. (Cue Fred Flintstone grumble-swearing.)
Still, get the vaccine. I gather Australia’s problem was a misjudgment about what to include in the vax.)
That article’s main point is that the “10%” refers to efficacy against H3N2 but in Australia when “it came to overall effectiveness against any of the multiple strains of flu, the vaccine worked about 30 percent of the time.” The other bit though is that the Australian program offers the flu vaccine for free through the National Program only to those at high risk (the elderly, those with at risk medical conditions, etc.), populations that typically have poorer responses to the vaccine than the younger and healthier, and have poor rates with the rest of the population, that responds better.
There’s an Australian selection bias for those most likely to respond poorly.
The best way to protect the high risk individuals is for the rest of us, especially the spewing fountains of germs that are otherwise healthy children, immunized as completely as possible, and thereby to minimize exposure of those at higher risk.
Putting that together with the already referenced study which showed that repeated vaccination is very effective compared to single season at preventing more serious to fatal compared to less serious cases … it seems the answer is complicated.
It’s been reported that Australia’s selection of flu viruses is not the same as ours; therefore preliminary estimates of how well the vaccine would work in the U.S. were too gloomy.
*"…a recent report in the journal F1000 Research found the Australian strain of H3N2 is not identical to the predominant virus circulating in the United States.
“The majority of the viruses are well-covered by the vaccine,” said lead researcher Dr. Slobodan Paessler, a professor in the department of pathology at the University of Texas Medical Branch in Galveston.
“There are some minor groups of viruses that are not well-covered,” he added."
“The current vaccine in the U.S., in contrast to the Australian [vaccine], will work because we have most of the American H3N2 viruses, rather than the Australian one,” Paessler explained."*
It is an interesting question. However, I would note that although the government subsidised free flu-vax is only for the at risk groups, the vaccination is very easy to get, and very cheap. Many companies provide it to employees for free, and you can get vaccinated at many pharmacies for the princely sum of $20 (15 USD.) Usually no harder than walk up, pay, roll up your sleeve. Vaccination rates for the flu in general seem to be of the order of 85%. The at risk groups seems to actually pull the average down, with only about 70% update.
The flu vaccination last year became a little controversial as many more died than usual, although not as bad as 2009. It came to the point where the government senior medical officer was denying that they had purchased sub-standard cheap vaccinations.
Where it seems some of the numbers became skewed was indeed that the predominant strain circulating (H3N2) was the one that causes more problems in the elderly. But there was an element of general dissatisfaction last year. But last year was an anomaly. You would not want to base general views on efficacy on 2017 in Oz.
So far, the effectiveness of the 2017-2018 flu vaccine in the US & Europe seems to be better than anticipated from the early results from Australia. But the flu season is just beginning to hit its peak here now.
Australia isn’t always a good predictor, for a couple of reasons:
the ‘origin’ of new flu strains is in Southeast Asia, quite close to Australia (and with lots of human travel between them). So the flu strains in Australia can be newer ones, mutated from the ones that were chosen last March/April to put in the vaccine. So the vaccine seems to be more effective here, where we are likely fighting off some of the older strains of the flu.
Australia seems to have a lower vaccination rate – mostly given to those seen as at risk. Here, it seems to be pushed for everybody. Especially children, who are often the vector for spreading flu. So the basic ‘herd immunity’ effect applies.
(I’ve also seen some questions about the Australian statistics. They are based only on patients who are sick enough to go to the doctor, not including patients who have mild cases or don’t get flu at all. I don’t know enough about statistics & disease to judge this, but personally, when I’ve had a case of flu, I didn’t bother going to the doctor – I knew what he’d say: “drink plenty of fluids, take aspirin, etc, for pain, and rest in bed”.)
That does raise an interesting related question: how / why does the human body’s immunesystem decide to Keep antibodies around at all, and for how Long? On the one Hand, the human Body in General takes as many energy saving measures as possible: muscles that aren’t used regularly are built back; bones that aren’t stressed regularly get thinner; the brain falls into repetitive Patterns as often as possible - so why do some antibodies stick around for life?
On the other Hand, Polio, measles, Tetanus are potentially deadly, so keeping antibodies against them forever would be a better choice.
So how does the immune System figure out “Those antibodies are important, Keep them” and “Those are less important, let’s Forget them to save Memory space”?
As a general rule, very general, your body will keep up immunity for about 10 years after a vaccination if you have no further exposure to the pathogen in that time. This is a reason for getting a tetanus/diphtheria/pertussis booster every ten years - most people aren’t exposed to those, so immunity fades with time.
Now, it used to be that something like a measles vaccination would be “for life” because the average person would be exposed to the disease from time to time, acting as a sort of natural booster. Now that we have beaten back such disease so thoroughly we’re finding adults are loosing their immunities due to lack of re-exposure.
So… basically, if your body doesn’t re-encounter something within 10 years it will tend to drop the immunity. If it does re-encounter it (you don’t have to be sick, just exposed) it will maintain the immunity. Very roughly - I’m sure that there are all sorts of conflating factors involved.
The conflating factors though are where it gets so fun!
The kicker in this is that immunity persistence is most easily measured (and inferred) by antibody levels but lasting functional immune protection is often provided without significant antibody levels by T cells that have persistent “memory” of the germ … which are not so easily measured. And how well those memory T cells develop may be impacted by age at exposure with early exposure potentially resulting in T cell memory protection that may be lifelong.