But I got this shot last year!

October 7, 2019 3:38 PM

Why are some vaccinations good for life and others need to be given every year or require periodic boosters?

I'm curious why some vaccinations (or should I say the body's immune response to them) provide a lifetime of immunity and others provide shorter term immunity.

As an example, I know that there are many variants of the flu, so that's one reason there are annual vaccinations, but it's my understanding that the immune response to the flu vaccination only provides protection for a limited time (measured in months rather than years).

I think for others such as tetanus it's something like every ten years.

Others such as measles, polio, etc. apparently provide a lifetime of immunity.

I'm sure the answer is probably complicated, but I'm willing to try to understand a complicated answer.

posted by Dansaman to Science & Nature (5 answers total)

It's based on how long it takes for the "memory" of the virus to decline over time.
posted by General Malaise at 4:21 PM on October 7, 2019

Measles doesn’t provide a lifetime of immunity. It’s just that before people stopped vaccinating their children, it was not a concern for adults. I had to get reimmuinzed just this year as an adult.
posted by Automocar at 5:22 PM on October 7, 2019 [7 favorites]

Hey, this is an area that is not at all well-understood by immunologists, but here’s a good and pretty recent article about it:

https://www.sciencemag.org/news/2019/04/how-long-do-vaccines-last-surprising-answers-may-help-protect-people-longer
posted by juliapangolin at 7:46 PM on October 7, 2019 [4 favorites]

Taking flu (yearly vaccines) and polio (rare vaccine) as examples, the short answer is that polio only affects humans while flu affects a wide variety of animals.

For a virus to mutate it need to be infecting and multiplying hosts. If a human isn't infected then polio isn't mutating. However, flu can infect a human, die off and still be incubating and multiplying in pigs, birds, cattle, you name it. When a human flu virus and an animal flu virus cross together they can form a new strain that the human immune system doesn't recognise, which is now infecting both the animals and humans, while always mutating and spreading. Swine flu (H1N1) and bird flu (H5N1) are recent examples. That's my memory from my virology work at least, hope it helps! Look up "genetic drift/shift" for a little more info on the mutation of influenza.
posted by Chaffinch at 6:39 AM on October 8, 2019 [1 favorite]

For most of these, the booster you get isn't any different year to year, so mutation doesn't make sense as an answer. I think the short version is, as juliapangolin's link explains, we don't really know yet what is different in the immune response and immune memory between different types of disease exposures.
posted by Lady Li at 10:21 AM on October 8, 2019