The article features a quiz from MedPage Today asking which vaccine has been associated with a reduced risk of dementia. The shingles vaccine reduces the risk of dementia by 20 percent, according to new studies. The study, led by Stanford University, used the 2013 vaccination policy in Wales and compared people born just before and after the date the program was introduced. Vaccinated persons had a lower incidence of dementia and mild cognitive impairment. Another study followed seniors vaccinated with Zostavax, and after seven years they had a 28 percent lower incidence of dementia compared to those not vaccinated. The vaccine also slows the progression of dementia and reduces the risk of dying from the disease by almost a third. The studies are observational in nature, so further research is needed to confirm causality.[1][2][3][4][5][6]