Do vaccines reduce the risk of dementia?

The benefits of vaccines in terms of infection prevention and cases of serious infection are widely recognized. It is important to recall the success of the vaccination against the SARS-COV-2 which considerably avoided the hospitalizations and the deaths due to the coronavirus. More and more studies also associate vaccines not only with infectious processes, but also with cardiovascular benefits. For example, several studies connecting influenza to prevention of acute myocardial infarction. ⁽¹⁾

Now let’s go even further and let’s talk about the protective effects of vaccines. Recently, in 2025, an independent study published in the journal Vaccine combines the recombinant vaccine with adjuvant against the zona (Shingrix) to a reduction in the risk of dementia. ⁽²⁾ We observe more and more that the prevention obtained by vaccination is significantly higher than what we knew so far. This retrospective cohort study, carried out from 2018 to 2022, mainly aimed to determine the impact of the recombinant vaccine with adjuvant administered against the zona on the development of dementia.

The secondary objectives were as follows:

• Evaluate whether vaccination by the recombinant vaccine with adjuvant decreased the risk of dementia.
• Identify a possible association between zona and antiviral treatment with dementia.

The data included was obtained from the registration of 4,502,678 people from the American database Optum Labs Data Warehouse. These people were aged 50 or over and had at least continuous records for 365 days in the database.

Three groups were determined based on vaccination by the recombinant vaccine with adjuvant against the zona:

• Not vaccinated (3,835,968 people): who had received no dose or until day 29 of the first dose.
• Partially vaccinated (206,297 people): who had received only 1^era dose or until day 29 of the 2^e dose.
• Completely vaccinated (460,413 people): which had received the 2 dose administered at least 30 days before or more.

The incidence rates observed were as follows:

• Not vaccinated: 135 cases for 10,000 people-years.
• Partially vaccinated: 108.2 cases for 10,000 people-years.
• Completely vaccinated: 99.1 cases for 10,000 people-years.

The results observed were promising with a significant reduction in the risk of dementia in vaccinated people. A decrease of 32 % of the risk of dementia was observed in subjects having received the 2 doses of vaccine, compared to non -vacinated (hazard ratio adjusted [HRa] : 0,68 [0,67 à 0,70] ; p <0.001). The reduction in risk (-11 %) was already noticeable in the group having received a single dose compared to non-vacuums (HRA: 0.89 [0,87 à 0,92] ; p <0.001). A reduction in risk has also been observed in people treated by antivirals, either in prevention, or due to the development of a zona, a herpes, or to prevent the reactivation of the Micken-Zona virus.

Several theories are developed to explain this protective effect: activation of innate immune cells when reactivating the chicken-zona virus, the release of cytokines and inflammatory chemokines, or vasculopathy which could deteriorate neurodegeneration.

Whatever the mechanism, the study highlights the importance of avoiding the development of the zona and enriches all other studies on the profits of this vaccine.

Despite this, the rate of vaccination in Spain in the adult population remains much lower than in the infant population and we must continue to recall all the advantages of vaccination and continue to recommend vaccines to our patients.

Even with all studies on the positive effect of vaccines, we still have difficulty convincing patients. This is why we must continue to insist that a vaccine is only beneficial if it is administered. In order to facilitate the dissemination of vaccination recommendations in each Spanish region, Samengen recently launched APP Vaccines Semergen. A application which allows, by indicating the region and the age of the person, to know which vaccine would be recommended to him and thus arouse the interest of patients. Because we must not forget, what is important is not the vaccine, but vaccination.

This article has been translated fromUnivadis.es. The content was reviewed by the editorial staff before publication.