Universal health coverage (UHC) is the vision that all countries provide affordable, quality preventive and curative healthcare to every person, everywhere. Besides helping to end extreme poverty and prevent 10 million deaths by 2035, this Sustainable Development Goal target is expected to also contribute to a grand convergence in health, where the poorest countries’ rates of mortality – infectious, infant and maternal – fall to levels currently only seen in the best performing middle income countries.

However, to achieve truly universal access will involve the strengthening and expansion of primary health care (PHC) in low and middle income countries. For example, building on those health interventions that most benefit vulnerable communities while simultaneously having the greatest reach—interventions like childhood immunisation.

Today, immunisations reach more children globally than any other child health intervention. Yet, despite progress in recent decades, we are still missing a large number of children.

To understand why, first consider how far we have come. This fall marks the 40th anniversary of the Alma-Ata Declaration, an international agreement that underlined the importance of PHC in achieving “Health for All”. Back then, barely 5 percent of the world’s children received routine immunization – measured as three doses of diphtheria-tetanus-pertussis-containing vaccine. Today that figure is 86 percent globally, or 82 percent if you just take into account the world’s poorest countries. That means considerably more children now have vaccination cards than birth certificates.

Despite such extraordinary progress, the challenge we now face is that the one-in-five children in the poorest parts of the world who are still missing out are not just the last to be reached, they are by far the hardest to reach. These children are living in the most impoverished and vulnerable communities, from remote rural villages to urban slums to conflict-affected communities. They are invisible to the health and welfare system of a country, not appearing in the often archaic, paper-based vital registration systems that certify births, deaths, and marriages. Given the low political voice of these populations, the fact that these children do not appear in any official records makes them easy to ignore, particularly in the absence of political will to serve these populations.

Birth registration and the use of digital identity technology has the potential to bridge that gap, by ensuring that every child has a unique identifier that can be used for birth records, medical records, and education records that stays with them through life. This may sound like a tall order for low-income countries that often barely even have stable power grids, but it is nevertheless highly achievable in a rapidly changing world where families have more access to mobile phones than toilets.

In some regions of Tanzania, for example, when mothers give birth at health facilities their babies are immediately enrolled onto the digital tablet-based Electronic Immunisation Registry (EIR). Those born outside health facilities are enrolled by community leaders, or later by health workers during their first vaccination. This means that from birth there is a digital record for each child, enabling health workers to keep track of their immunization status across entire districts, even as families move between health facilities, clinics and outreach sessions.

This system then acts as a platform for broader health interventions, including access to nutritional supplements, malaria prevention and deworming treatments. And now the Tanzanian government is in the process of integrating all maternal health services, family planning and other services, meaning that once a child is registered she or he should be able to benefit from all services.

Created under the leadership of the Government of Tanzania and with support from key partners including the Bill & Melinda Gates Foundation, PATH, JSI and UNICEF, and with plans to roll the system out nationwide with Gavi support, the EIR is just one example of what can be achieved with digital technology. We need to see more of this. In particular, this is an opportunity for private sector engagement in the UHC agenda. Besides its current role in building stronger PHC through data systems, logistics, data and smarter financing, there is a need for the private sector to invest and engage with governments and bring its expertise and innovation to develop scalable digital identity solutions too.

We know that one-in-four children globally, and closer to one-in-two in Africa, do not formally exist because their birth was never registered. This is more than just administrative oversight. It’s at the heart of how governments improve the lives of its citizens. Beyond protecting children’s health, birth registration is capable of helping protect children’s futures. By linking into education and training services, we can not only achieve universal health coverage, but can also prevent the fifth child from becoming an invisible generation when they are older.

*Seth Berkley is the CEO of Gavi, The Vaccine Alliance and Henrietta Fore is the Executive Director of UNICEF