ABSTRACT The SARS-CoV-2 pandemic has had a devastating impact on the US population with over 25 million positive cases and over 450,000 deaths as of early February, 2021. In no population has the impact of this virus been more apparent than in the elderly, those with significant co-morbidities and particularly the elderly living with dementia. All population-based analyses find that the risk of mortality increases logarithmically with age. Indeed, even in the frail nursing home population, advanced age has a substantial influence on COVID mortality. Furthermore, a diagnosis of Alzheimer’s Disease and Related Dementias (ADRD) appears to confer an excess risk of morbidity and mortality, whether in a nursing home or not. Fortunately, there are now several vaccines approved for use in adult populations. These not only are highly effective but appear safe. Brown investigators, under a supplement to the NIA funded ADRD IMPACT Collaboratory [3U54AG063546-02S5], have found no increase in short term mortality and no CDC defined significant adverse events among vaccinated nursing home residents. While vaccine supply continues to be locally restricted, major US pharmacies like CVS and Walgreens have been engaged in the vaccination of millions of their customers at their stores around the country beginning the second week of February. In spite of positive data from a population of vaccinated nursing home residents, monitoring rare adverse events requires very large populations which is what this supplemental sample of Walgreens customers represents adding to the CVS Medicare population being studied under the [3U54AG063546-02S7] award. The need for a larger population is particularly important because those with ADRD already suffering from neurodegenerative diseases may be at greater risk of serious neurological adverse events of vaccines. In addition, the unknown potential for adverse events may result in high rates of incomplete vaccination (both shots) among older adults. Such uncertainty contributes to vaccine hesitancy and may result in large disparities in SARS-CoV-2 vaccination among racial/ethnic groups, for which disparities in seasonal influenza vaccination already exist. Incomplete vaccination may be more common among those with ADRD due to dependence on a caregiver for transportation. Since society cannot wait to vaccinate this population with an effective vaccine, we must establish an active post-vaccination surveillance system of a large population to report vaccine safety. This proposal to add Walgreens Pharmacies data to the existing effort to match Pharmacy customer records with Medicare claims to create a data infrastructure that is updated weekly will characterize who is vaccinated, monitor adverse reactions to vaccination and examine the rate of “break through” infection with COVID. Adding data from Walgreen’s 13,231,175 million Medicare beneficiary pharmacy customers allows us to track the immediate and long term effects of vaccinatio...