Effect of Messaging on Pragmatic Outcomes Within an Integrated Healthcare System

The Effect of Messaging on Pragmatic Outcomes Within an Integrated Healthcare System: A Randomized Trial (EMPOWeR) study is designed to learn whether vaccine reminder messages that highlight a patient's choice of COVID-19 vaccines can help increase vaccine uptake among adults who are at higher risk for serious illness from COVID-19. The study will take place within KPSC, a large integrated health care system in southern California, and will use routine health care messages and reminders for updated COVID-19 immunization .

COVID-19 vaccination rates have declined since 2022, including among older adults and people with medical conditions that increase their risk of severe disease. Concerns about vaccine side effects, trust, and vaccine technologies may influence whether people choose to get vaccinated. The EMPOWeR study will evaluate whether providing information about vaccine choices can encourage individuals at higher risk of severe COVID-19 to receive an updated COVID-19 vaccine.

Adults who are eligible for a COVID-19 vaccine and who meet the study eligibility criteria will be included in the study. Eligible participants include adults enrolled for care at KPSC who are either 65 years of age or adults aged 18 to 64 years with certain health conditions that place them at increased risk for severe COVID-19 illness. Participants will not be asked to attend study visits or complete surveys. The study will use immunization data already collected in electronic health records as part of routine care.

Participants will be randomly assigned to one of five groups. One group will receive a standard COVID-19 vaccine reminder message currently used in routine care. The other four groups will receive messages that provide information about available COVID-19 vaccine options: mRNA and protein-based COVID-19 vaccines. These messages may:

• Inform participants that they can choose between two different COVID-19 vaccine types.
• Explain differences between vaccine technologies.
• Include information that both vaccine options are supported by health care professionals.
• Provide information about vaccine side effects and vaccine choice.

All messages will be delivered to eligible participants in early October 2026 using the participant's usual communication preferred language (i.e., English or Spanish). Follow-up reminder messages will also be sent later in the vaccination season (in early December 2026).

The main goal of the study is to determine whether these different messages increase receipt of the updated 2026-2027 COVID-19 vaccine. Additional goals include type of COVID-19 vaccine received receipt of an influenza vaccine, receiving influenza and COVID-19 vaccines on the same day, and the time between the reminder message and COVID-19 vaccination.

The study is designed to reflect real-world clinical practice. Participants will continue to receive routine medical care, and all vaccines will be provided through standard care processes. Researchers will compare vaccination outcomes across the different message groups to determine which communication approach is most effective for increasing vaccination uptake among high-risk adults.

This study may help health care systems better understand how to communicate with patients about vaccine options and improve vaccination coverage among populations at increased risk for severe COVID-19 illness.

Inclusion criteria

• Aged ≥18 years;
• Active KPSC member;
• Continuous membership from 27 August 2025 to 27 September 2026;
• Members who are aged 65 years and older, or adults aged 18-64 years with at least one of the following health conditions that increases their risk for severe COVID-19 illness, including: a) asthma, b) cancer, c) ischemic stroke, d) intracerebral or subarachnoid hemorrhage, e) transient ischemic attack, f) chronic kidney disease, g) dialysis, h) bronchiectasis, i) chronic obstructive, pulmonary disease (COPD), j) pulmonary fibrosis, k) cystic fibrosis, l) pulmonary hypertension, m) cirrhosis, n) non-alcoholic fatty liver disease (NALD), o) alcoholic liver disease, p) autoimmune hepatitis, q) diabetes, r) heart failure, s) coronary artery disease, t) cardiomyopathy, u) HIV, v) obesity, w) essential hypertension, x) primary immunodeficiency and other underlying immunocompromising conditions, y) solid organ or blood stem cell transplant, z) tuberculosis;
• No documented receipt of updated 2026-27 COVID-19 vaccine as of 28 September 2026;
• Has valid email information.

Exclusion criteria

• Unable to receive or opted out of email communication.
• People who cannot safely receive a COVID-19 vaccine, including those who had a severe allergic reaction to a previous COVID-19 vaccine or have a contraindication to COVID-19 vaccine or a vaccine ingredient, will not be included in the study.
• People who are pregnant or breastfeeding will not be included.