Nudge Podcast Summary: "This Single Text Made Girls 45% More Likely to Get Vaccinated"
Release Date: July 7, 2025
Introduction
In this compelling episode of Nudge, host Phil Agnew delves into the powerful influence of behavioral science on public health initiatives. The episode, titled "This Single Text Made Girls 45% More Likely to Get Vaccinated," explores how subtle messaging can significantly impact vaccination rates among young girls in Georgia. Through insightful discussions with experts from the Behavioural Insights Team and a personal experiment by Phil himself, listeners gain a deep understanding of the endowment effect and its practical applications.
Understanding the Endowment Effect
Phil begins by sharing a personal anecdote to illustrate the endowment effect—a cognitive bias where individuals ascribe more value to things merely because they own them.
Phil Agnew [00:02]: "After the second viewing, something interesting happened. I mentally started to imagine moving in...I started to feel like I already owned the house. This is the endowment effect."
He references a study by Sutherland mentioned in the book Irrationality, highlighting how ownership alters perceived value:
Phil Agnew [01:30]: "Those who picked their numbers wanted $8.67 to give up the ticket. It was the same ticket, the same odds, but a huge difference in how much they were valued."
Behavioural Insights Team's Intervention in Georgia
Phil introduces his guests, Giulia Tagliaferri and Niall Daly from the Behavioural Insights Team (BIT), also known as the Nudge Unit. Established in 2010 within the British government, BIT has evolved into an international organization addressing global behavioral challenges.
Giulia Tagliaferri [03:40]: "Over 95% of cervical cancer is caused by HPV infection. In Georgia, it's the third leading cause of female cancer deaths."
Despite the availability of free HPV vaccines, Georgia faced alarmingly low vaccination rates, especially post-pandemic, plunging to around 14%.
Designing the SMS Intervention
Niall explains BIT's strategic approach to tackling this issue using behavioral science principles:
Niall Daly [05:04]: "Framing a vaccine as being reserved for someone or reserved for a person in your care has been found to be particularly effective."
Referencing a pivotal study by Katie Milkman and colleagues, Niall highlights the effectiveness of personalized messaging:
Phil Agnew [06:03]: "The most effective message out of all 19 was one that simply said that the vaccine was reserved for you. Just adding that line boosted vaccination rates by 4.6% compared to the control group."
Implementing the SMS Trial
In collaboration with UNICEF Georgia and the National Centre for Disease Control (NCDC), BIT conducted a large-scale SMS campaign targeting over 55,000 girls aged 10 to 12. Four variants of text messages were tested alongside a control group that received no reminders.
Niall Daly [08:39]: "We tested four variants of the text message...and the fourth version was the social proof version."
The variants included:
- Basic Reminder: Notification of the free HPV vaccine and encouragement to contact local clinics.
- Extended Information: Included links to NCDC's website for additional information.
- Reserved Messaging: Emphasized that the vaccine was reserved specifically for the recipient at their clinic.
- Social Proof: Highlighted that over 118 million girls worldwide had safely received the vaccine.
Results of the Intervention
After a 62-day trial period, the results were promising:
Niall Daly [11:31]: "Version three of our SMS reminder, which had 4.7%, found that this reserved for her framing had approximately 65% greater odds in terms of a girl receiving the vaccine relative to the control group."
While the control group saw a 2.4% vaccination rate, the reserved messaging variant achieved a 4.7% uptake, demonstrating the profound impact of perceived ownership.
Niall Daly [12:41]: "Before they knew about the vaccine being reserved for their daughter...they didn't feel possession of it. Once we imbue that sense of possession...our brains value things more."
Phil Agnew's Personal Experiment
Inspired by the success in Georgia, Phil decided to apply the endowment effect to his own marketing efforts. He tested two email variants among his latest 1,000 newsletter subscribers:
- Control Version: Offered a 50% discount with a generic subject line.
- Reserved Version: Emphasized that the discount was reserved specifically for the recipient, mentioning "reserved" four times.
Contrary to expectations, the reserved framing backfired:
Phil Agnew [17:33]: "Clicks on the email...were 14% lower. The reserved for you framing led to zero sales."
Reflecting on the outcome, Phil identifies key differences between his approach and the successful Georgia trial:
Phil Agnew [18:34]: "Julia mentioned that the reserved for her framing works best if the message feels like it's specifically tailored...and if there's a scarcity element."
He acknowledges that his message lacked personalization, exclusivity, and urgency—critical components that made the vaccination messages effective.
Key Takeaways and Reflections
Phil concludes by emphasizing that while behavioral science offers valuable insights, its application requires careful consideration of context and audience. Not all nudges are universally effective, and understanding the underlying mechanisms is crucial for success.
Phil Agnew [20:00]: "Behavioural science provides guidance that has been proven to work elsewhere, so might work for you. But it's not foolproof."
He encourages listeners to explore further by visiting the Behavioural Insights Team's website and reading their published papers for a deeper understanding of behavioral interventions.
Conclusion
This episode of Nudge masterfully illustrates the potency of the endowment effect in influencing behaviors, particularly in public health. Through expert insights and real-world experiments, Phil Agnew showcases both the successes and challenges of applying behavioral science principles. The story underscores the importance of tailored, context-specific strategies in effectively leveraging psychological biases to drive meaningful change.
For those interested in the detailed results and methodologies, Phil directs listeners to the show notes, where data and further readings are available.
Notable Quotes with Timestamps:
- Phil Agnew [00:02]: "This is the endowment effect."
- Giulia Tagliaferri [03:40]: "Over 95% of cervical cancer is caused by HPV infection."
- Niall Daly [05:04]: "Framing a vaccine as being reserved for someone...has been found to be particularly effective."
- Phil Agnew [06:03]: "Adding that line 'reserved for you' boosted vaccination rates by 4.6%."
- Niall Daly [11:31]: "Reserved for her framing had approximately 65% greater odds..."
- Phil Agnew [18:34]: "The message made out that they had reserved a specific vaccine for them at their local clinic."
Further Resources:
- Access the full study and email experiments here via the show notes.
- Visit the Behavioural Insights Team website for more research and publications.
- Subscribe to the Nudge newsletter for ongoing insights and updates.