A friend thinks that being infected with a new influenza virus means that little immunity is gained, unless you get a vaccine. But, he is forgetting that new strains can make current vaccines out-dated.

I'm sure the immune system will "remember" that particular strain just as well as getting a vaccine.

When someone gets infected with the influenza, and gains some immunity, is that immunity just as good as getting it from a vaccine?

  • $\begingroup$ Hi and welcome SE isn't for settling arguments. However, generally speaking - yes. $\endgroup$
    – Andrew
    Commented Sep 7, 2020 at 0:03
  • $\begingroup$ @Andrew Perhaps I can get information, statistics or something that could convince him. $\endgroup$
    – The T
    Commented Sep 7, 2020 at 0:05
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    $\begingroup$ @Andrew there's no reason that someone couldn't come here with a valid question to settle an argument or debate, it happens all the time. That's what factual knowledge is for, to dispel inaccuracies. $\endgroup$
    – MattDMo
    Commented Sep 8, 2020 at 2:42
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    $\begingroup$ Not really answerable, unless you define what you mean by "just as good". If you get immunity to (a particular strain of) the influenza virus via a vaccine, you don't have to experience having the flu. If you get it from having the flu, you do. IMHO that makes the vaccine better :-) $\endgroup$
    – jamesqf
    Commented Sep 8, 2020 at 2:51
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    $\begingroup$ @Andrew It's all about the subject matter and the way the question is posed. If a debate is purely opinion-based, too broad, or otherwise not on topic for the particular site, then it should be closed as such. If it is on topic, like this one, it should be accepted. IMO, whether or not there's a debate or argument at the root of the question is irrelevant. You shouldn't have been criticized for that. $\endgroup$
    – MattDMo
    Commented Sep 8, 2020 at 14:41

2 Answers 2


Yes, infection-acquired immunity is (generally speaking) just as good as, if not better than, getting vaccinated. Remember, the whole point of a vaccine is to simulate an infection and stimulate immunity without having to suffer through the actual symptoms of a real infection, potentially getting very sick or even dying. This is regardless of whether it's a "new" strain of virus or not.

† Not all exposures lead to good immunity, whether via infection or vaccination. Many times this can be related to immunosuppression or other immune system defects, but age and other factors like co-morbidities can also play roles as well.

  • $\begingroup$ For your addendum, the same can be said for some exposures that produce minor illness even when the immune system is functioning well. $\endgroup$
    – Bryan Krause
    Commented Sep 8, 2020 at 17:02

Natural infections almost always yield a better immunity than that acquired through vaccination. However, vaccines yield a better immune-response than getting infected with influenza. That is so to say the side effects.

I want to backtrack to part of your questions where you say I'm sure the immune system will "remember" that particular strain just as well as getting a vaccine. and add a little bit of interesting information regarding influenza.

Some Influenza (A) stereotypes that infect humans are: H1N1, H2N2, H5N1, etc... The H stands for Hemagglutinin and N is Neuraminidase. These are important in vaccine development. The H and N are proteins located on the surface of the virus and allow for entry into a cell for infection.

Strains are classified according to their hemagluttinins and neuraminidases. Every year when the vaccine for the seasonal flu is developed we don't know with 100% certainty which strain might be the most prevalent. Rather, surveillance data is used in deciding which flu might be the most prevalent. More info on the CDC Website.

So back to the question:

Does the immune system remember that particular strain just as well as getting a vaccine?

Yes it does and there's a paper in PNAS that looked at something similar. This is related to something called “Immunological Honeymoon”. A theory that the first infection during childhood provides stronger immunological memory than a later infection.

Ecess mortality in 1918 and the childhood exposure/cohort immunity model.

The paper found that people who were 28 year old were more susceptible to the Spanish Flu (H1N1) in 1918 because they had been exposed to the wrong virus as children.

The elderly, however, had been exposed to H1N1 as children and were well protected. People who were middle aged or in their teens in 1918 had been exposed to H1N8 as children and were partially protected.

This I recon is just as good as vaccine, but more to show that the immunity acquired through infection is, in fact, remembered. For how long? That's a totally different question that varies from infection to infection. Some are life-long (such as measles), other are short lived requiring re-infection, or booster shoots in case of vaccination.


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