Won’t an aspect like the reduced risk of Alzheimer from some vaccines, if this is causal, be likely to more then offset the effect of reduced immunological space?
“We then show that receiving the herpes zoster vaccine reduced the probability of a new dementia diagnosis over a follow-up period of seven years by 3.5 percentage points (95% CI: 0.6 – 7.1, p=0.019), corresponding to a 19.9% relative reduction in the occurrence of dementia.”
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In many people yes, but in others no. It depends on your relative risk of Alzheimer’s vs your risk of respiratory infections like pneumonia.
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Olafurpall:
Besides probably causing a reduction in Alzheimer, the vaccinations guard against the diseases they are meant for. Can’t the combined effect be likely to yield a net benefit to most people?
Yes, in most people it probably is a net benefit.
Any opinion on taking an antiviral as well?
Because I have an APOE4 allele, about 3 x causal increase in risk for Alzheimer’s - it is very worth it to me with vaccines.
Antivirals could be of benefit and they would not cause a reduction in immunological space. They might have some other side effects though. I can’t say I have looked into them much at all so I can’t give a good opinion on them.
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The BCG (Bacillus Calmette-Guérin) vaccine was developed against Tuberculosis over 100 years ago, but it is known to protect against other infectious diseases as well. A Phase III randomized clinical trial from Harvard shows that multiple doses of the BCG vaccine protected adults with Type I diabetes from COVID infections better than the initial mRNA COVID vaccines. It also protected this group against other infectious diseases. The BCG vaccine worked against COVID variants Delta and Omicron in this study.
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Apparently even freeze dried BCG has cold storage requirements. Though I see some conflicting evidence of this online.
This study indicates it does seem to lose potency, but should still be effective up to 2 months at room temperature.
https://www.sciencedirect.com/science/article/abs/pii/S0007097163800078
Other sources from googling all state it must be kept in cold storage.
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Some professions like nursery workers and healthcare care workers are exposed to far more infectious pathogens in the course of their careers than the average person let alone more solitary professions like crop farming. I would have thought this would place a far greater burden on finite immunological memory than a few optional vaccines.
Is there any evidence that these people have weaker immune systems as a result?
It’s not necessarily going to put a far greater burden on immunological space than vaccines. Vaccines are designed to create a response resulting in a strong immunity, which will take up a decent amount of immunological space. But it’s hard to compare these things. I can’t say whether getting lots of vaccines matters more or less than getting lots of infections over a lifetime. I haven’t looked into that, and the studies I read on immunological space did not talk about that.
I’m not aware of direct evidence that people exposed to more pathogens have weaker immune systems or less immunological space at older ages, but I can’t say I have looked at the literature on this in any detail. It would be interesting to see studies on immunological space in people with very different life histories when it comes to infection exposure.
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https://www.thelancet.com/journals/eclinm/article/PIIS2589-5370(24)00195-0/fulltext
In contrast to the beneficial off-target effects reported following neonatal BCG in infants, a small increased risk of symptomatic febrile or respiratory illness was observed in the 12 months following BCG vaccination in adults.
It seems like adults could also get vaccinated just for the sake of anti-aging. Even though RCTs show no real benefits, there aren’t many risks either—it feels like a ‘better than nothing’ situation. I wouldn’t make it a priority, though. @KarlT @DrFraser @RapAdmin
I’m fascinated by vaccines and association data in regard to Dementia. So I had Vera-Health.ai do it’s best with the common vaccines. I guess my conclusion is, there are much better options to use than BCG vaccine. Additionally, I doubt that risk reduction is additive; and once there has been some risk reduction, adding another vaccine will almost certainly have diminishing returns.
Looks like Shingles Vaccine is a good one to start with; and furthermore, if one has HSV-1 IgG Ab, strongly consider 500 mg of Valacyclovir daily … which also will suppress VZV in addition to HSV-1. Interestingly, no increased risk of dementia if one has HSV-2.
Percent dementia reduction (vaccine-specific; “regular schedule” where data fit that use)
| Vaccine | Best available % dementia reduction (from provided sources) | What outcome/time horizon it reflects | Clinical Evidence |
|---|---|---|---|
| Shingles (recombinant zoster vaccine; RZV/Shingrix, 2-dose series) | 51% lower risk (aHR 0.49) vs unvaccinated | Incident all-cause dementia; follow-up started 6 months after dose 2; mean follow-up 3.4y | Retrospective matched cohort (Kaiser Permanente; n=65,800 vaccinated; 263,200 unvaccinated), Nature Communications 2026—largest schedule-concordant RZV study here; still significant vs Tdap comparator (aHR 0.73) suggesting residual “healthy vaccinee” bias but persistent association 1 |
| Shingles (live attenuated zoster vaccine; ZVL/Zostavax—no longer used in US) | ~2.0 percentage-point absolute reduction in new dementia dx over 5.5y (eligibility natural experiment) | Incident dementia diagnoses over 5.5y | Natural experiment/regression discontinuity (Ontario; n=464,637), Lancet Neurology 2026; estimates more plausibly causal than standard observational designs 2 |
| Shingles (live attenuated zoster vaccine; ZVL) | ~1.8 percentage-point absolute reduction in new dementia dx over 7.4y (eligibility quasi-experiment) | Incident dementia diagnoses over 7.4y | Regression discontinuity (Australia; n=101,219), JAMA 2025 3 |
| Influenza (annual vaccination) | 13% lower risk (RR 0.87) | Incident dementia | Systematic review/meta-analysis (21 observational studies; n=104,031,186), Age and Ageing 2025; vaccine-type pooled association across heterogeneous cohorts 4 |
| Influenza (dose-response; repeated annual vaccination) | 16% lower risk with 2–3 doses (HR 0.84) and 57% lower risk with ≥4 doses (HR 0.43) | Incident dementia; high-risk populations only | Systematic review/meta-analysis (8 cohort studies; n=9,938,696), Age and Ageing 2025—most relevant numeric estimates for “regular schedule” over multiple years; not significant in overall population (HR 0.93) 5 |
| Pneumovax (PPSV23) / pneumococcal vaccination | No single pooled “any dementia” % in provided sources; 33% lower AD risk (RR 0.67) and 36% lower AD risk (RR 0.64) reported in 2 meta-analyses (AD ≠ all-cause dementia) | Alzheimer’s disease risk (not all-cause dementia) | Two observational meta-analyses: Frontiers in Immunology 2022 (pneumococcal OR 0.71 → 29% lower AD risk) 6 and Age and Ageing 2025 (pneumococcal RR 0.64 → 36% lower AD risk) 4 |
| Tetanus + Diphtheria (Td/Tdap) | 33% lower risk (RR 0.67) (any dementia) | Incident all-cause dementia | Observational meta-analysis (21 studies; n=104,031,186), Age and Ageing 2025 4 |
| BCG (routine vaccination) | Not available in provided sources | — | Available estimates are primarily from intravesical BCG in bladder cancer (not routine vaccination), and a bladder-cancer meta-analysis reports HR ~0.63–0.65 but with high heterogeneity and “minimal if any” effect—this is not generalizable to routine BCG schedules 7 |
| RSV (routine older-adult vaccination) | Not available as a schedule-based % in provided sources | — | One NPJ Vaccines propensity-matched cohort reports reduced 18-month dementia risk after AS01-adjuvanted shingles/RSV vaccines, but the abstract provided does not include a percent/HR and follow-up is short 8 |
| COVID-19 | Not available in provided sources | — | No human observational/clinical estimates of dementia reduction after COVID vaccination are provided here (only animal/other outcomes) 9 |
Bottom line (using the provided sources): the strongest and most directly schedule-concordant dementia-risk reduction signal is for recombinant zoster vaccine (2-dose series) (about 51% lower dementia risk vs unvaccinated in a large matched cohort) 1, while influenza and Td/Tdap show modest-to-moderate associations (with a notable dose-response for repeated annual influenza vaccination in high-risk groups) 5 4.
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Would you recommend the shingles vaccine for a 22-year-old guy? It’s strictly for anti-aging purposes. To be honest, I’m really tempted.
Hi Cole,
As much as I cannot give you specific medical advice - I think that you likely have been immunized for VZV as a child and unless you actually had chickenpox - I’m not really seeing the Shingles vaccine would have any value - AT LEAST on the logic of this suppressing VZV as you’ll not have any in your body. If there comes forth data showing the shingles vaccine to provide such benefit in individuals who have never had VZV … which I’d be surprised by such a finding; then I’d change my view.
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There is some incidence among younger (30-39) populations and it’s increasing:
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Shingles is a clinical diagnosis - and I see a number of cases where clinicians call something shingles that isn’t. Irrespective, the issue is VZV native infection rate. The transition zone as vaccination started ~1995 is really to look at folks in their 20’s - and many of these with VZV natively weren’t immunized. So the point remains in a 22 year old, if no infection with VZV … then I question the benefit of this vaccine in any age, and the risk is low in that agegroup, but very high in those pre and peri-statrt of the Varicella Vaccine.
Summary of approximate % who have had natural chickenpox:
- Age ~20: ~5–15%
- Age ~30: ~20–40%
- Age ~60: ~95–99%+
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Personally, chicken pox at 5 years old (mild case). Shingles at 21 years old (likely stress related).
Now at 45 not yet eligible for shingles vax though I’d like to have it for both avoiding shingles again and for the dementia related risk reduction.
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Can this be understood as: based on the data, I can get vaccinated at age 30 instead, because the risk at 30 is similar to that in people over 50?
We can even infer the risk for people in their 20s is probably similar to that for those in their 30s. However, it has been proven that the current vaccine provides protection for at least 11 years, and model projections suggest it can offer effective protection for at least 20 years. The only concern is: if we wait until age 40–50 to get a booster shot, will the vaccine’s efficacy be weaker than the first dose?
Since you’re a zoomer get the HPV vaccine Gardasil 9 if you haven’t already, that’ll reduce your lifetime cancer risk.
The shingles risk is double for 50+ compared to 30+. Yeah people get shingles in their 30’s.
This thread is good for all the vaccines and which ones you might be missing, and booster schedules: Vaccines for longevity
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