Cervical cancer is one of the leading causes of cancer-related deaths among women in low- and middle-income countries, and the safe and effective HPV vaccine is key to prevention. But despite significant efforts to promote vaccination through national immunization programs and free access, a considerable segment of the population remains unvaccinated—a challenge that has much to do with lack of awareness, incorrect information and apprehension.
Several initiatives have been launched to help achieve the goal of reaching 90% coverage of HPV vaccination in girls by age 15, a target recommended by international organizations. Behavioral science techniques could be helpful, providing a complementary and cost-effective approach to better inform the public. These could be especially effective in situations where vaccine supply is plentiful, but demand remains low, and confidence in vaccination has been weakened. Nonetheless, the effectiveness of behavioral interventions in developing countries has been insufficiently explored.
The Case of Colombia
The need to employ such alternative strategies arose when the Expanded Program on Immunization, a program led by Colombia’s Ministry of Health and Social Protection, engaged with the IDB to explore ways to improve HPV vaccination rates. This engagement led to a behavioral intervention in collaboration with the Secretary of Health of Cali, aimed at better informing the public and boosting immunization efforts.
The HPV vaccine is widely available in Colombia, but demand is particularly low. This was not always the case. When the HPV vaccine was included in the national immunization program in 2012, the country achieved remarkable results, achieving a 95% vaccination rate among the targeted population within just two years.
However, in 2014, 15 women from the city of Carmen de Bolívar who had received the vaccine were admitted to the hospital with abdominal pain, headaches, dizziness, and fainting—an incident that received extensive media coverage. Despite subsequent studies showing no association between the symptoms and the vaccine, HPV immunization rates dropped to less than 15% by 2016 and have remained low because of concerns about the vaccine, its removal from the list of vaccines provided at school, and a decrease in the number of doctors recommending it fearing parental backlash.
Can a Text Message Help Rebuild Trust?
In Cali, where the HPV immunization rate had dropped below 10%, the situation was particularly worrisome. So, we designed an SMS intervention to provide parents information about the vaccine and the benefits of vaccinating their daughters against HPV, reaching over 15,000 parents. The campaign tested four types of messages, each designed to address a specific barrier to HPV vaccination:
- Information on the vaccine: clear and concise information regarding the effectiveness of the vaccine, its availability free of cost, and the location of vaccine centers.
- Social norms: highlighting the widespread acceptance and use of the vaccine.
- Trust-building: enhancing confidence in the vaccine through recommendations by doctors and Cali’s Health Secretariat.
- Framing: using different framing strategies, such as reminding parents to complete their daughters’ vaccination schedule, emphasizing the vaccine’s safety, and the risks of getting cervical cancer without vaccination.
Each group received weekly SMS messages for eight weeks. The messages also incorporated other behavioral strategies, including personalized messages. A control group did not receive any messages; a placebo group received messages unrelated to HPV vaccines.
The results were promising. Across all the groups, the messages led to an increase in vaccination rates, ranging from 34% to 55%, depending on the treatment. The messages that focused on rebuilding trust in the vaccine appeared to be particularly impactful, suggesting that restoring confidence may be a key factor in improving vaccination uptake. Altogether, the takeaway was clear: behaviorally informed messages are effective, even in environments with high hesitancy. Moreover, the intervention proved to be highly cost-effective, yielding between $3.60 and $5.75 in economic benefits for every dollar spent, underscoring the potential for substantial public health and economic returns.
A Tool for Governments to Improve Vaccination Rates
Rebuilding confidence in vaccines is challenging, especially after public trust has been eroded, as happened in Cali. However, this intervention demonstrates that with the right approach, it can be achieved. By directly addressing the psychological and informational barriers behind beneficiary concerns regarding vaccines, behavioral strategies can enhance efforts to increase vaccine uptake, even in settings where confidence has been severely compromised. Beyond this case, this experience also points to a broader opportunity. Low-cost behavioral interventions, such as SMS campaigns, can be adapted to address hesitancy in other public health challenges. By understanding what holds people back, and designing strategies that respond to those concerns, behavioral science offers a scalable and cost-effective way to reengage with the public and support informed health decisions.
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