Could COVID-19 vaccines guard against dementia?

COVID-19 vaccines could potentially guard against dementia and Alzheimer’s disease, according to an op-ed in WSJ. 

COVID-19 infection itself can lead to long-term cognitive decline in some individuals and can accelerate Alzheimer’s symptoms, concluded an Alzheimer’s Association study. An Alzheimer’s Research & Therapy echoed those findings. 

Pointing to data suggesting that vaccinations against tetanus and flu lead to reduced Alzheimer’s incidence in seniors, the WSJ article notes that a systemic immune response from vaccines could lower brain inflammation and thus protect brain neurons. 

The thesis is not new. For example, a 2001 study in the Canadian Medical Association Journal theorized that prior vaccination against diphtheria or tetanus, poliomyelitis and influenza could protect against Alzheimer’s disease.

And last July, the Alzheimer’s Association published a study making similar claims. Researchers have correlated flu and pneumonia vaccinations with a reduced Alzheimer’s risk. In particular, pneumonia vaccination led to up to a 40% reduced incidence of Alzheimer’s risk in some individuals. On average, people aged 65 to 75 had a 25% to 30% lower incidence of developing Alzheimer’s when adjusting for gender, race and other factors. 

The Alzheimer’s Association study found that seniors who had at least one flu vaccination had a 17% reduction in Alzheimer’s incidence. In addition, more frequent flu vaccination appeared to lead to an additional 13% reduced incidence. 

Of course, reduced Alzheimer’s incidence in vaccinated individuals does not necessarily indicate a causal relationship. People who obtain vaccines may be more likely to be healthier and seek regular medical care than the unvaccinated. 

But the WSJ article notes a growing amount of data reflecting the trend continues to surface, including a study in the Journals of Gerontology in April that found a 42% lower incidence of Alzheimer’s rate in recipients of the Tdap (tetanus, diphtheria and pertussis) vaccine. 

Similarly, a study in Vaccines found that people over 75 who received the Bacillus Calmette–Guérin (BCG) vaccine had a 27% reduced Alzheimer’s incidence 3.5 to 7 years afterward. 

A separate study in Clinical Genitourinary Cancer concluded that bladder-cancer patients who received the BCG vaccine had a 60% reduced incidence of dementia, including Alzheimer’s disease.