Age-appropriate Completion and Coverage of Key Childhood Vaccines in Greater Accra, Ghana, 2014–2023

Imagine a giant, bustling city where millions of people live, work, and move around every day. In this city, there is a special kind of "superpower shield" that protects children from invisible, dangerous monsters called diseases. These shields aren't made of metal or magic; they are vaccines. Think of vaccines like training sessions for your body's internal security team. When a child gets a shot, it's like showing their security team a "wanted poster" of a germ so they know exactly how to fight it if it ever shows up.

For this training to work perfectly, the security team needs to see the posters at the right time. If a child gets the first poster but misses the second one, or if they get them all but wait too long, the training is incomplete, and the child remains vulnerable. Scientists and health workers care deeply about this because when enough people have their shields up, the whole city becomes safe, and the monsters can't spread. But in a fast-moving, crowded city, it's hard to make sure every single child gets their full set of training on schedule. This is the puzzle that researchers in Ghana set out to solve: Are the kids in the busy capital city getting their full protection, and are they getting it on time?

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The Big Picture: A Ten-Year Shield Check

A team of health detectives in Ghana decided to look at the "shield records" for children in the Greater Accra Region—the country's most crowded and fast-moving area. They didn't just look at one year; they dug into ten years of data, from 2014 to 2023, using a giant digital filing cabinet called DHIMS2 that tracks every shot given at hospitals and clinics. Their goal was to answer two main questions: How many children are getting all their shots (completion), and how many are getting them at the right age (timeliness)?

The Good News: The Shield is Getting Stronger

The story starts with some encouraging trends. Over the decade, the number of children who received their full set of vaccines grew significantly. By 2023, about 80.5% of children aged 12 to 23 months were considered "fully immunised," meaning they had received all the necessary doses for their age group. This was a huge jump from 51.9% back in 2014.

One specific vaccine, the Pentavalent (which protects against five different diseases), showed a particularly strong recovery. Its coverage climbed from 67.8% in 2014 to a massive 96.5% by 2023. This suggests that the health system is getting really good at reaching children and getting them their shots, even in a chaotic, urban environment.

The Plot Twist: The Pandemic Pause

However, the story isn't a straight line up. The researchers found a big dip in the middle of the decade. In 2020 and 2021, during the global COVID-19 pandemic, vaccination coverage took a nosedive. The "shield training" sessions were interrupted, and fewer children got their shots on time.

For example, the percentage of babies (0–11 months) who got their full schedule of shots dropped from a high of 47.1% in 2019 down to 38.3% in 2020. It took a couple of years for the numbers to bounce back, but by 2023, the region had mostly recovered, showing that the health system is resilient and can bounce back after a crisis.

The Mystery of the "Negative Dropouts"

Here is where the story gets a bit weird and fascinating. Usually, when you start a training course (like getting the first dose of a vaccine), some people drop out before finishing (getting the third dose). This is called a "dropout rate," and it's usually a positive number.

But in Greater Accra, the researchers found something strange: the "dropout rate" for the Pentavalent vaccine turned negative. By 2023, the rate was -16.8%.

What does a negative dropout mean? It sounds impossible, like saying you lost less than nothing. In reality, it means that more children were recorded as getting the third dose than the first dose in the same year. The researchers suggest this isn't because children are time-traveling. Instead, it likely happens because the city is so full of people moving in and out. A child might get their first shot in a different region and come to Accra later for their third shot. Or, it could be a sign that the health records are a bit mixed up, counting the same child twice or estimating the number of children in the city incorrectly. It's a signal that while the numbers look great, the data might be a little fuzzy.

The "Too Good to Be True" Problem

The researchers also spotted another red flag: in some districts, the vaccination coverage numbers were over 100%. For instance, one district reported 138.2% coverage for the Pentavalent vaccine, and another reported 288.9% for the Measles-Rubella vaccine.

Obviously, you can't vaccinate more children than exist. The paper explains that this doesn't mean the health workers are superhuman; it means the math is off. It suggests that the "denominator" (the estimated number of children living there) might be too low, or the "numerator" (the number of shots recorded) might include children who live elsewhere. It's like trying to count apples in a basket but accidentally counting apples from a neighbor's basket too. This tells the researchers that while the health workers are doing a great job, the way they count and report the data needs to be cleaned up.

The Uneven Map

Finally, the team used a map to see where the shields were working best. They found that the coverage wasn't the same everywhere. Some districts were "Green Zones" with over 90% coverage, hitting the World Health Organization's target. But others were "Red Zones" with less than 60%.

Specifically, by 2023, only 45% (13 out of 29) of the districts had reached the 90% target for the second dose of the Measles-Rubella vaccine. This means that while the city as a whole is doing better, some neighborhoods are still left behind, leaving children there vulnerable to outbreaks.

The Bottom Line

The paper concludes that Greater Accra has made impressive progress and has shown it can recover from big disruptions like the pandemic. The health system is strong, and more children are getting vaccinated than ever before. However, the "negative dropouts" and the "over-100%" numbers are warning signs that the data isn't perfect. To make sure every single child is truly protected, the health workers need to fix how they count children and ensure that the kids in the hardest-to-reach neighborhoods get their full set of shields on time. The shield is getting stronger, but it's not quite perfect yet.