Reducing immunization inequities among zero-dose and under-vaccinated children through catch-up vaccination in Burkina Faso: findings from a mixed-method evaluation of the Big Catch-Up initiative, 2023–2025

In many parts of the world, a child's health depends heavily on a simple, scheduled series of shots that protect against diseases like measles, polio, and whooping cough. These vaccines are a cornerstone of public health, designed to stop outbreaks before they start and to keep children safe from illnesses that can be fatal or cause lifelong disability. However, when a country faces a perfect storm of crises—such as a global pandemic combined with ongoing violence and instability—these life-saving services often break down. Health clinics close, roads become impassable, and families are forced to flee their homes. In these chaotic conditions, the most vulnerable children are the first to be left behind. They are the ones who never receive even a single dose of a vaccine, known as "zero-dose" children, or those who receive some shots but miss others, leaving them only partially protected. Without intervention, these gaps in protection can lead to deadly outbreaks of preventable diseases, undoing years of progress in child survival.

A recent evaluation from Burkina Faso offers a clear look at how a nation attempted to fix this broken system. Following the disruptions of the pandemic and years of insecurity, the country launched a massive effort called the "Big Catch-Up" initiative between 2023 and 2025. The goal was straightforward but ambitious: find the children who had missed their routine shots, bring them in for vaccination, and strengthen the daily health services that would prevent this from happening again. Researchers from the World Health Organization and the Ministry of Health of Burkina Faso studied this effort to see what worked, what didn't, and how they managed to reach families in some of the most difficult-to-access areas. Their findings paint a picture of a complex struggle where success was possible, but only through intense community effort and flexible strategies that adapted to a harsh reality.

The initiative focused on children between the ages of one and five who had fallen behind on their immunizations. The team targeted six specific regions in the country, chosen because they represented a mix of accessible areas and those that were hard to reach due to geography or safety concerns. To understand the full picture, the researchers did not just look at numbers on a spreadsheet. They went into the field, observing how vaccination teams worked and interviewing hundreds of people involved in the process. These included health officials, doctors, nurses, community health workers, local leaders, and the parents of young children. They wanted to know how the plan was made, how it was carried out on the ground, and what barriers stood in the way.

The results showed that the initiative made significant progress in reaching the children who needed it most. By the end of 2025, the program had successfully vaccinated 144,245 children who had never received any vaccines before. This represented about two-thirds of the original target for this group. Even more notably, they reached 200,624 children who had started their vaccinations but had not finished the full series, surpassing the initial goal for these "under-vaccinated" children by a wide margin. The effort was particularly effective at finding children who were older than the typical age for routine shots, reaching many who were between one and two years old, and a substantial number between two and five years old. This suggested that the campaign successfully looked beyond the usual infant clinics to find children who had been missed as they grew older.

Beyond just the big catch-up campaign, the initiative helped improve the regular, day-to-day vaccination services that families rely on. After the program began, the number of children receiving their first and third doses of a combined vaccine that protects against five different diseases increased across most of the regions studied. The number of children getting their second dose of a measles vaccine also went up. This improvement was not just a result of the special campaign; it indicated that the routine health system itself was becoming stronger and more capable of reaching children. One key factor in this success was the decision to combine vaccination with other essential health services. Instead of asking families to make multiple trips for different needs, health workers offered vitamin supplements and deworming treatments at the same time as the shots. This integrated approach made it easier for parents to bring their children in and ensured that the visit addressed multiple health needs at once.

The study also highlighted that reaching these children required more than just medical supplies; it required deep trust and cooperation with the community. In many areas, local leaders and community health workers played a critical role. They helped identify families who were missing out on care and encouraged parents to bring their children to vaccination sites. In some cases, these leaders went door-to-door or used local radio stations to share messages about the importance of vaccines, helping to overcome hesitation or fear. The researchers found that when health workers adapted their strategies to fit the local context—such as changing the timing of visits or using different locations to meet people where they were—the program worked much better.

However, the path to success was far from smooth, and the evaluation made it clear that significant obstacles remain. The most persistent barrier was insecurity. In areas where violence was high, health workers could not always reach certain villages, and vaccination sites had to be postponed or moved. This instability also made it difficult to keep health staff in place, as workers often had to leave dangerous areas or were unable to travel to their posts. Logistical challenges were also a major hurdle; a lack of reliable internet made it hard for staff to report their data on time, and shortages of equipment to keep vaccines cold threatened the safety of the doses. Furthermore, while sociocultural resistance to vaccines was not a major issue in the areas studied, rumors and misinformation about vaccines continued to circulate, creating pockets of hesitation that required careful attention.

The researchers concluded that while the Big Catch-Up initiative was a success in reducing the number of unvaccinated children, the work is not finished. The gains made during this period need to be protected and made permanent. To do this, the country must continue to integrate catch-up efforts into its regular health services, ensuring that no child is missed simply because they are older or live in a remote area. It will also require continued investment in the health system, including better support for staff in insecure regions and improved infrastructure to handle data and logistics. The study suggests that in fragile settings, where crises are common, the only way to ensure every child is protected is to build a system that is flexible, community-centered, and ready to adapt when the ground shifts beneath it. The effort in Burkina Faso demonstrates that even in the face of severe challenges, it is possible to find the missing children and give them the protection they deserve, but it requires a sustained commitment to equity and resilience.