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The two significant mRNA vaccines are for COVID and there effect is only about 6 months. Is there a cause and effect relationship here? That is, do mRNA vaccines tend to only last a short period of time?

Here is a site that says natural immunity should last for at last 7 months:Natural Immunity

Here is a site that says the vaccine should last for at least 6 months:How long the vaccine lasts

I would hope that the vaccine would last longer. Perhaps, that is not a reasonable expectation on my part.

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    There are no other mRNA vaccines available. Do you have a citation for the effect only lasting 6 months? Do you have a comparison citation for immunity after natural infection by COVID-19 or other coronaviruses? Questions here are required to show evidence of prior research.
    – Bryan Krause ♦
    Commented Dec 6, 2022 at 17:36
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    If the vaccine lasts as long as natural immunity, does it make any sense to say the mRNA vaccine works a short period of time? There's no practical difference between 6 and 7 months, it's not like a binary where immunity is present and then it's not.
    – Bryan Krause ♦
    Commented Dec 6, 2022 at 19:27
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    It depends on what you consider "working" to mean. If it's sterilizing immunity, the vaccine works for as long as you have enough antibodies to prevent the pathogens from replicating. But the immune system is complex and antibodies are just a small piece of the puzzle. You will have immune cells trained to recognize the antigen and react to it according to their functions (attack, alarm, make antibodies) for years to come, potentially for the rest of your life. In that sense, the vaccine works for a long time. You might get sick, but will recover faster.
    – JohnEye
    Commented Dec 7, 2022 at 16:50
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    This is a great question. Right now, Polio vaccination is generally considered lifelong, and, as far as I can tell, none of the currently available Polio vaccines are mRNA. If a new, mRNA-based Polio vaccine were developed (not that it would, go with the hypothetical for a moment), would we expect it to also be lifelong or would we say something like "well, it's mRNA and not the old stuff, so you'll probably need a booster next year"?.
    – Robert Columbia
    Commented Dec 7, 2022 at 17:58
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    How do you expect anyone to say what mRNA vaccines "tend" to do, when we don't have enough examples to determine any tendencies?
    – Barmar
    Commented Dec 7, 2022 at 19:01

1 Answer 1

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Short answer - no, the mRNA vaccines specifically don't only work for a short period of time. Natural infection and all vaccines of different types against SARS-CoV-2 all produce similar durations of immunity.

Longer answer:

Generally speaking we can expect the immunity from a vaccine to last approximately long as the immunity following a natural infection, though there are some exceptions to this, where vaccination (not via mRNA) results in shorter protection than natural infection for pertussis1 . In the case of infection with SARS-CoV-2, the natural immunity induced by the infection results in protective levels of antibodies for about 6 months to a year and similar time-frames for vaccines of any sort against SARS-CoV-2.

I found a relatively recent paper in PNAS2 (highly respected journal), that states (emphasis mine):

Peak antibody levels elicited by messenger RNA (mRNA) vaccines mRNA-1273 and BNT1262b2 exceeded that of natural infection and are expected to typically yield more durable protection against breakthrough infections (median 29.6 mo; 5 to 95% quantiles 10.9 mo to 7.9 y) than natural infection (median 21.5 mo; 5 to 95% quantiles 3.5 mo to 7.1 y). Relative to mRNA-1273 and BNT1262b2, viral vector vaccines ChAdOx1 and Ad26.COV2.S exhibit similar peak anti-S IgG antibody responses to that from natural infection and are projected to yield lower, shorter-term protection against breakthrough infection (median 22.4 mo and 5 to 95% quantiles 4.3 mo to 7.2 y; and median 20.5 mo and 5 to 95% quantiles 2.6 mo to 7.0 y; respectively).

From this you can see that the durations of protection are similar in length between the various vaccine types and similar to natural infection.

The Conversation has a nice layman's explanation of how this all works and why infection and vaccinations don't typically produce different durations of immunity,

1:Leung T, Campbell PT, Hughes BD, Frascoli F, McCaw JM. Infection-acquired versus vaccine-acquired immunity in an SIRWS model. Infect Dis Model. 2018 Jun 15;3:118-135. doi: 10.1016/j.idm.2018.06.002. PMID: 30839933; PMCID: PMC6326260.

2:Townsend JP, Hassler HB, Sah P, Galvani AP, Dornburg A. The durability of natural infection and vaccine-induced immunity against future infection by SARS-CoV-2. Proc Natl Acad Sci U S A. 2022 Aug 2;119(31):e2204336119. doi: 10.1073/pnas.2204336119. Epub 2022 Jul 15. PMID: 35858382; PMCID: PMC9351502.

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