Transient recovery and renewed decline in HPV vaccination coverage in Cameroon after single-dose and gender-neutral vaccination: a secondary analysis of national immunisation coverage estimates, 2020–2025
This secondary analysis of Cameroon's 2020–2025 immunization data reveals that despite an initial surge in HPV vaccination following the 2023 shift to a single-dose, gender-neutral schedule, coverage subsequently plummeted due to HPV-specific delivery and sustainability barriers rather than general system weakness, necessitating a targeted, girls-first recovery strategy.
Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer
Cervical cancer is a devastating disease that claims the lives of thousands of women in Cameroon every year. It is caused by a virus called the human papillomavirus, or HPV, which is so common that nearly everyone who is sexually active will encounter it at some point. Fortunately, a vaccine exists that can prevent this infection before it ever takes hold. The challenge lies not in the science of the vaccine, but in the logistics of getting it into the arms of the people who need it most: adolescent girls. In many places, delivering health care to teenagers is difficult because they are not in the same places as young children, and they require different kinds of trust and permission from their families and communities. When a country tries to roll out a new vaccine, it is like building a bridge across a wide river; the engineers must design the structure to hold the weight, but they also must ensure the road leading to it is clear, the materials are available, and the local people are willing to cross it.
In Cameroon, health officials faced a complex puzzle regarding this vaccine. For years, the country followed a standard rule that required children to receive two shots of the HPV vaccine to be fully protected. However, the data showed a troubling pattern: many girls received the first shot but never returned for the second. In 2021, for every one hundred girls who got the first dose, only about twenty-four completed the full series. By 2022, the situation had barely improved, with roughly thirty girls out of one hundred finishing the course. This meant that the majority of the effort was wasted, leaving most girls unprotected. To fix this, the government made a bold decision in January 2023 to switch to a single-dose schedule, a change supported by global health experts which meant that one shot would be enough for full protection. They also decided to offer the vaccine to boys, not just girls, in an effort to be fair and stop the virus from spreading further.
The results of this change were immediate and dramatic. In 2023, the number of girls receiving the vaccine nearly tripled, jumping from a low of 23 percent the year before to 68 percent. This surge was driven by a combination of the simpler one-shot rule, a special push to reach schools and communities, and the inclusion of boys. It looked as though the country had finally solved the problem. But the story did not end there. Instead of holding steady at this high level, the numbers began to slip. By 2024, coverage had fallen to 36 percent, and by 2025, it had dropped again to just 30 percent. The country had climbed a steep hill only to slide back down, losing the ground it had gained in just two years.
Researchers set out to understand why this happened. They looked closely at the data, comparing the HPV vaccine numbers with the performance of other routine vaccines given to babies, such as those for measles and polio. They found something surprising: while the HPV numbers were crashing, the coverage for all eleven other vaccines actually improved or stayed steady during the same period. This told the researchers that the problem was not a general failure of the health system or a lack of medicine in the country. If the whole system were broken, all the numbers would have gone down together. Instead, the issue was specific to the HPV program and the unique challenges of reaching teenagers.
The analysis pointed to several specific hurdles that caused the decline. One major factor was the strain of trying to vaccinate both boys and girls at the same time. While including boys is a noble goal for long-term fairness, it doubled the number of people the health workers had to reach, requiring more vaccine doses, more transport, and more planning. When the initial excitement of the 2023 campaign faded, the system struggled to maintain this expanded effort, and the focus on girls—the group most at risk of cervical cancer—got diluted. Another significant barrier was the relationship with faith-based institutions. A large portion of schools and health centers in Cameroon are run by religious groups, particularly the Catholic Church. In some areas, these institutions had restricted access to the vaccine due to concerns or opposition, effectively closing off a major pathway to reach thousands of children. The researchers noted that while some religious leaders were helpful, the lack of a unified, trusted message from all faith groups created gaps where the vaccine could not reach.
There were also issues with the supply chain and communication. Even though the country had enough vaccines for other diseases, the HPV program faced its own shortages and delays in getting doses to the right places. Furthermore, the shift to a single dose required a clear explanation to parents and teachers. Without consistent messaging, some people remained unsure if one shot was truly enough, or they held onto old fears about the vaccine's safety. The researchers found that the initial surge in 2023 was likely a temporary boost from a concentrated effort, but once that effort slowed down, the underlying weaknesses in the system were exposed.
The study concludes that the path forward requires a change in strategy. The authors suggest that the country should temporarily focus its resources on getting the highest possible coverage among girls before expanding the routine program to include boys again. This would allow health workers to stabilize the system, secure a reliable supply of vaccines, and rebuild trust with communities and religious leaders. They emphasize that the vaccine must be delivered through schools, where teenagers are already gathered, and that this delivery needs to be protected and planned carefully, rather than treated as an occasional event. The researchers also stress the need for a long-term plan to engage religious leaders and address misinformation directly.
Ultimately, the paper shows that a single policy change, like switching from two shots to one, is not a magic solution. It can open the door, but keeping the door open requires constant effort, reliable supplies, and the active support of the community. The decline in coverage was not a sign that the vaccine stopped working, but a signal that the system supporting it was not yet strong enough to sustain the change. By understanding these specific obstacles, health officials can now work to build a more resilient program that ensures every girl in Cameroon has the chance to be protected from a deadly disease.
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