More children are immunized today than ever before, and the number of new vaccines that children in poor countries have access to is also at its highest. This means that globally children have never been better protected against infectious disease in history. But while this is true in terms of absolute numbers, the latest data reveal some worrying new trends when you look at the proportion of children protected.

The first trend confirms our fears that the global percentage of children receiving routine immunization—as measured by three doses of a diphtheria-tetanus-pertussis vaccine, or DTP3—has stagnated, levelling off at 85 percent. The second, perhaps even more alarming, is that despite falling from 28 million in 2000 to around 16 million today, the number of children in the world’s 68 poorest countries that are missing out on DTP3 has now started to rise.

Although neither of these detract from the astounding progress we’ve made in recent decades, with increases in immunization coverage helping to halve childhood mortality since 1990, it is serious cause for concern. Even though the increase is not huge, it suggests a lack of commitment on routine immunization and a need for a new level of engagement and focus, at a truly critical time, if we are to avoid sliding even further backwards.

To understand why, consider the challenges we are up against. Each year the number of children in need of vaccination increases and is likely to continue to do so for some years. This means that even to just maintain a steady level of childhood immunization we need to reach more children each year, 2.8 million more children globally to be precise, since 2010.

In addition to this, the number of children living in fragile countries is steadily increasing. Whether this is because of conflict, economic decline or the results of climate-related pressures, people living in such countries are inherently vulnerable and can be more difficult to reach. Our analysis of the latest annual WHO/UNICEF Estimates of National Immunization Coverage (WUENIC) data, published last week, suggests that in poor countries nearly half of all children missing out on DTP3 live in fragile states.

To some extent, this is to be expected and partially reflects global migrations trends, with more than 68 million people displaced from their homes, more than at any time since World War II. There is no easy fix for this growing problem. Whether we are talking about Rohingya refugees fleeing persecution in Cox’s Bazar, in Bangladesh, or Syrian civilians trapped between fighting factions, each situation is unique and requires a tailored solution to address the breakdown in access to health systems.

But, while there are many complex and intractable reasons for why we are not reaching children in fragile states, in non-fragile countries the situation should be much clearer. There is, however, too much focus on mass immunization campaigns, which are often expensive, take health workers away from routine services and often come in response to outbreaks. This detracts from where the real focus should be, strengthening routine immunization services and building strong primary health care systems. So, at a point when we could expect to see fewer children missing out in non-fragile than in fragile states, instead we are finding that we are not even keeping up with population increases.

We have to get this under control again. This will require new level of commitment from countries towards strengthening primary health care systems and will need continued investment in vaccine supply chains and real-time data systems. As the number of children vaccinated increases, and as we introduce new vaccines to broaden the level of protection against other diseases like pneumonia and diarrhea as well as liver and cervical cancer, this will inevitably place greater pressure on existing infrastructure, such as transport and fridge capacity. But this is necessary if we are to continue to progress. 

When the WHO first introduced the Expanded Program on Immunization in 1974, fewer than 5 percent of children in developing countries were vaccinated. Since then, the lives of millions of the most vulnerable children have been transformed through increased access to vaccines. With the continued support of WHO, UNICEF and Gavi, the Vaccine Alliance, developing countries can continue to progress. But it’s important to remember that this progress doesn’t just mean increasing the number of children that are protected against killer infectious diseases; it also means reducing the number of children that are missing out, as no child should die of vaccine-preventable disease.