This experiment is part of a megastudy with a total of ten experimental conditions and a holdout control condition to which patients will be randomly assigned. Ther focal comparison in this experiment is between a message encouraging vaccination by reminding participants that the holiday season is just a few weeks away and getting vaccinated will allow them to more safely gather with loved ones and a control message telling patients that an updated COVID booster vaccine is waiting for them. The intervention testing if text messages encouraging vaccination by reminding participants that the holiday season is just a few weeks away and getting vaccinated will allow them to more safely gather with loved ones will produce more vaccinations than otherwise identical messages.

Exclusion Criteria:

1. The patient unsubscribed from texts before the send date and time of the patient's SMS/MMS message
2. The patient received a bivalent COVID booster before the send date and time of the patient's SMS/MMS message.

As treated participants will receive text messages, there is no scope for blinding. Care providers will not be made aware of subjects' participation in the study, or assigned treatment arms. The study team will only receive data on subjects' assigned arms and outcomes at the end of the study.