Recent research showed that the shingles vaccine reduces the risk of developing dementia. Now, a new study found that the vaccine may slow the progression of dementia in those already diagnosed with the devastating disease.

In the United States, an estimated 6 million people are currently living with dementia. This number is expected to rise in the coming years as the population ages. There is no cure, but a promising new study suggests that getting a two-shot dose of the shingles vaccine could slow down the progression of the devastating disease.

Shingles is a viral infection caused by the varicella-zoster virus, the same virus responsible for chickenpox. After a person recovers from chickenpox, the virus can remain dormant in nerve tissue and reactivate later in life, leading to shingles. The condition typically results in a painful rash and can also cause nerve pain that persists even after the rash has healed.

The vaccine is estimated to be more than 90% effective in preventing shingles in older adults, but new research, including a study published this week in the journal Cell, points to its benefits for dementia.

Earlier this year, researchers reported that the shingles vaccine cuts the risk of developing dementia by 20% over a seven-year period. Now a large follow-up study has found that shingles vaccination may protect against risks at different stages of dementia — including for people already diagnosed.

The new study found that the vaccine could also have therapeutic properties against dementia, by slowing the progression of the disease, leading to a reduced risk of dying from the disease.

“We see an effect on your probability of dying from dementia among those who already have dementia,” Dr. Pascal Geldsetzer, assistant professor of medicine at Stanford University and senior author of the new study, according to CNN.

“That means that the vaccine doesn’t just have a preventive potential, but actually a therapeutic potential as a treatment, because we see some benefits already among those who have dementia,” he said. “To me, this was really exciting to see and unexpected.”

The researchers analyzed data from older adults in both Wales and Australia who had similar characteristics and lifestyle patterns and found that people who were vaccinated did have a lower risk of being diagnosed with cognitive impairment and subsequently dying from dementia.

Key points from the research:

• The vaccine was not only associated with a 20% reduction of dementia diagnoses, but also a 3.1% reduction in diagnoses of mild cognitive impairment over nine years.

• The shingles vaccine decreased deaths due to dementia by 29.5%. Even when looking at all-cause mortality, the shingles vaccine was associated with a 22.7% reduction.

• The protective effects seemed to be stronger among women than men.

Geldsetzer suggested that the vaccine may lower inflammation in the body by reducing the activation of the shingles virus. He said that inflammation is the root cause of many chronic diseases, and that dementia is no exception. The other possibility is that the vaccine boosts the immune system to help fight off infections which research has linked to causing dementia.

The downside of the study is that researchers analyzed people who received an older shingles vaccine which is now longer used in the U.S., Europe and Australia, according to The Washington Post. It has since been replaced with the Shingrix vaccine, which is more effective at preventing shingles and may also be associated with a lower risk of dementia, but more studies would be needed.

The Centers for Disease Control and Prevention recommends two doses of a shingles vaccine for adults 50 and older or those 19 and older with a weakened immune system. Researchers are pushing for more clinical trials to understand why the vaccine is protective, which can teach us something fundamental about dementia and help develop better treatments.