Efficacy of Communication Modalities for Promoting Flu Shots

The Centers for Disease Control (CDC) recommends a flu vaccination to everyone aged 6+ months, with rare exception; almost anyone can benefit from the vaccine, which can reduce illnesses, missed work, hospitalizations, and death. Flu shots are particularly important for patients at high risk of experiencing severe outcomes.

During the 2020-21 and 2021-22 flu seasons, the study team sent messages to Geisinger patients in the top 10% of risk for flu and complications according to an artificial intelligence algorithm. Messages that told patients they were at high risk significantly increased their likelihood of getting vaccinated.

The present study will extend previous work by testing which modality or modalities are most effective at boosting flu shot rates in patients at high risk. In previous campaigns, patients received messages via all communication modalities patients were eligible for (mailed letter, SMS text, and/or patient portal message). In this study, patients will be randomized to receive high-risk messages in one or more modalities.

• Letter (Behavioral): Mailed letter about flu vaccination
• Patient portal (Behavioral): Patient portal message about flu vaccination
• SMS (Behavioral): SMS about flu vaccination

Primary outcomes

• Flu vaccination [4 weeks after the first messages are sent in the study]: Flu vaccination within 4 weeks of the first message send date

Other outcomes

• High confidence flu diagnosis [Up to 8 months]: Patient received a flu diagnosis via a positive polymerase chain reaction (PCR)/antigen/molecular test (yes/no) during the 2022-23 flu season (from the first message send date through April 30, 2023).
• "Likely flu" diagnosis [Up to 8 months]: Received a "high confidence flu" diagnosis (with positive PCR/antigen/molecular test) and/or "likely flu" diagnosis (as assessed via International Classification of Disease \[ICD\] codes or Tamiflu administration or positive PCR/antigen/molecular test) (yes/no) during the 2022-23 flu season (from the first message send date through April 30, 2023). Note that "likely flu" is a superset of the "high confidence flu" diagnoses.
• Flu complications [Up to 11 months]: Diagnosed with flu-related complications (yes/no) from the first message send date through July 31, 2023.
• ER visits [Up to 11 months]: Number of ER visits from the first message send date through July 31, 2023.
• Hospitalizations [Up to 11 months]: Number of hospitalizations from the first message send date through July 31, 2023.
• COVID-19 vaccination rates [Up to 8 months]: Received at least one COVID-19 vaccination (yes/no) during the 2022-23 flu season (from the first message send date through April 30, 2023).

Sex: All, ages: 18 Years to any

Inclusion Criteria:

* Included on a list of active Geisinger patients (all patients on this list attended at least one primary care appointment at Geisinger between 10/1/2008 and 4/13/2022, and either had a Geisinger primary care provider assigned as of April 2022, or were in the Electronic Health Record \[EHR\] since at least September 2021 and had at least one encounter in 2020-2022)
* Aged 18 or older
* In the top 10% of risk for flu and flu complications, according to Medial's flu complications machine learning algorithm (which operates on coded EHR data)
* Has a Geisinger PCP assigned as of August 2022
* Has had an encounter in the last 2 years as of August 2022

Exclusion Criteria:

\- Cannot be contacted via any of the communication modalities (e.g., letter, patient portal, SMS) being used in the study, either due to insufficient/missing contact information in the EHR or because they opted out of all modalities

• Study Protocol and Statistical Analysis Plan (PDF, 2022-10-06)

• Christopher Chabris, PhD, Principal investigator, Geisinger Clinic