Preliminary research shows that the shingles vaccine can provide some level of stroke protection for seniors.

For this study, researchers at the U.S. Centers for Disease Control and Prevention reviewed Medicare records for more than one million patients over the age of 66 years. All of the patients had received the shingles vaccine between 2208 and 2014; the incidence of stroke was tracked for four years afterward.

The overall stroke risk dropped 20 percent for patients under the age of 80 years who received the shingles vaccine. In patients 80 years and older, the risk dropped about 10 percent.

Shingles is a viral infection that has been tied to an increased risk of stroke. It is caused by the chickenpox virus and is characterized by a painful bout of rashes and blisters. For patients who have previously had chickenpox, there is a greater risk for eventually developing shingles. The vaccine can reduce the shingles risk by about half. The CDC recommends that all adults age 50 and older get the shingles vaccine.

The research team, led by senior scientist Quanhe Yang, found that stroke protection from the shingles vaccine was particularly strong among patients between 66 and 79 years of age.

It’s unclear what the cause of the reduced stroke risk is, but it might have something to do with inflammation. Patients who have shingles have a greater risk of heart attack and stroke due to the body’s inflammatory response to the illness.

Peer-review and follow-up research using the CDC’s preferred shingles vaccine is needed. The study was performed with a vaccine that is no longer the vaccine of choice.