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When people with an upcoming doctor’s appointment get a text reminder about receiving a flu vaccination, it increases the likelihood that they will get immunized when they come in, particularly if the message states the shot is “reserved” for them, new evidence reveals.

“Our take home message is that text message reminders are effective for increasing vaccination uptake — and the best ones communicate to patients that a vaccine is reserved for you,” said Dena M. Gromet, PhD.

“This strategy capitalizes on a well-studied behavioral science phenomenon: A reserved vaccine feels like it belongs to you, so it feels like a loss to give it up,” added Gromet, executive director of Behavior Change for Good Initiative at the University of Pennsylvania in Philadelphia.

The study was published online April 29 in PNAS.

Could Work for COVID-19

The researchers focused on which message tactics worked best for primary care offices offering the flu vaccine — but the strategy also could apply to COVID-19 vaccinations, a study author and other experts said.

“Although uptake of the COVID-19 vaccine comes with a unique set of challenges,” Gromet said, “we expect that for those who are open to getting vaccinated but haven’t followed through, these types of reminders will be an effective nudge toward vaccination.”

It is a “very interesting study with significant implications for boosting vaccination rates, such as for COVID-19,” David Kaelber, MD, told Medscape Medical News when asked to comment.  

Dr David Kaelber

“I would expect a similar effect if this strategy were applied to COVID-19 vaccinations as well,” added Kaelber, professor of Internal Medicine, Pediatrics, and Population and Quantitative Health Sciences at Case Western Reserve University in Cleveland, Ohio.

Dr Julie C. Jacobson Vann

Along with lead author Katherine Milkman, PhD, and colleagues, Gromet studied 19 possible text message scripts, combinations, and timing to increase uptake of vaccination. They compared vaccination rates among messages sent to 37,304 patients at two institutions versus people who did not receive such reminders.

Based on other research, “this seems to be a reasonable approach to also increase vaccination rates for COVID-19,” Julie C. Jacobson Vann, PhD, MS, RN, from the University of North Carolina at Chapel Hill School of Nursing, said in an email.

Stick With Your Style

In addition to a greater obligation to follow through when they believe a vaccine is reserved for them, patients also responded best to text messages along the lines of typical communications from their doctor’s office.

In other words, it is best to avoid trying to be particularly creative or funny.

“We were surprised to find in our post-hoc analyses that more interactive and informal messages did not perform as well,” Gromet said. “In fact, some of our most clever interventions were among the least effective.”

A message with a picture of a dog telling a cat a joke about spreading the flu, for example, did not work particularly well.

A Messaging “Megastudy”

Gromet and colleagues conducted a megastudy, a field experiment where different teams of scientists test multiple interventions in the same population and on the same outcome. In this case, they assessed 47,306 patients coming to Penn Medicine or Geisinger Health for a new or routine primary care appointment in the fall 2020.

They randomly assigned patients to one of the 19 text messaging strategies or to the control group. None had received a flu shot already, according to their electronic health record.

Average age was 52 years, 43% were male, and 70% were white. Although electronic health records indicated that none of the patients had yet received a flu shot, 47% had received one during the previous flu season.

“I think many of us have a sense that automated texting/messaging about immunizations outside of or in conjunction with an in-person visit should improve immunization rates some,” Kaelber said. “What is great about this study is that it looks at many different ways to do this and therefore is prescriptive about ways to text/message that are more or less effective.”

Clinically Effective and Cost-effective?

All 19 text messaging strategies increased vaccination rates by an average 2.1 percentage points. “Although the average 2.1 percentage point difference in influenza vaccination rates between the text message participants and comparison participants is small, the overall effect has the potential to be substantial if applied to large populations,” Jacobson Vann said.

The most effective approach was a two-pronged approach: One message sent 72 hours before an appointment noting that “it’s flu season,” “a flu vaccine is available for you,” and “a vaccine reminder” would be sent before the appointment. A second text sent 24 hours in advance simply stated that “this is a reminder that a flu vaccine has been reserved for your appointment.”

This intervention was associated with a 4.6 percentage point boost in vaccination at the cost of sending two text messages, or less than 10 cents, the researchers note.

The investigators also calculated a more conservative estimate and found this strategy associated with a 2.8 percentage point boost in vaccination, or a 6.7% increase. 

“Even though a 6.7% improvement in vaccination rates might not seem like too much, at the population level, considering everyone who should receive a vaccine like the influenza vaccine or the COVID-19 vaccine, this increase in vaccination rates will result in millions and millions of more people being vaccinated,” Kaelber said.

Next Steps

Gromet and colleagues also conducted a similar study with Walmart pharmacy patients. Preliminary findings include a similar top-performing message that the flu vaccine was “waiting for you.”

“We’re eager for opportunities to test messages specifically for COVID-19 vaccinations and to examine other types of nudges that could help encourage vaccination,” Gromet added.

PNAS. Published online April 29, 2021. Full text

Gromet, Kaelber, and Jacobson Vann disclosed no relevant financial relationships. The National Institute on Aging, the Bill and Melinda Gates Foundation, the Flu Lab, and the Penn Center for Precision Medicine Accelerator Fund supported the study. The AKO Foundation, John Alexander, Mark J. Leder, and Warren G. Lichtenstein provided additional support.

Damian McNamara is a staff journalist based in Miami. He covers a wide range of medical specialties, including infectious diseases, gastroenterology, and critical care. Follow Damian on Twitter: @MedReporter.

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