At the United Nations meeting in New York late last month, attendees started to refer to the new Sustainable Development Goals by a different name. The aims morphed into the Global Goals for sustainable development, or just Global Goals.

Whatever we call them, if the goals are to achieve what they set out to, the next few weeks will be crucial. At the end of this month, a UN expert group will meet to try to agree on how to measure progress — and success or failure.

Each of the 17 goals is made up of several targets — 169 in all. Global Goal 3, for example — to “ensure healthy lives and promote well-being for all at all ages” — includes a target to achieve universal health coverage (UHC). UHC is something that the World Health Organization has been pushing for since 2005, asking all countries to provide comprehensive health care for all citizens at an affordable cost.

The UN is exploring having each of these 169 targets judged against two 'indicators'. But what can best indicate UHC? Unlike the Millennium Development Goals (MDGs) that preceded them, the Global Goals focus on both rich and poor countries. 'Universal' really must mean everyone.

No other health intervention reaches so many people.

One way to indicate progress towards UHC is to measure access to health interventions. But which treatments should we choose? Shine the spotlight on one and another is cast into the shadows. And how important is it for everyone to have access to the same treatments anyway? A child with type 1 diabetes growing up in Kansas clearly does not need the same access to mosquito nets as a child living in Somalia. And should we judge the health of the Somalian child on the basis of their access to blood-glucose monitoring?

Given the challenge of trying to capture this complexity in a single measure, the UN is exploring having an indicator for UHC that is broken down into sub-indicators, which it calls tracers. Possible tracers include access to treatments for tuberculosis, hypertension and diabetes, as well as access to antiretroviral therapy and preventative measures for neglected tropical diseases. Others include improved sanitation, having a skilled attendant present during births, provision of insecticide-treated bed nets and access to full childhood immunization. In some countries, the list could extend to mental-health provision, treatment for cataracts, palliative care and other interventions.

At first glance, the list looks balanced. It reflects a good cross-section of disease burden, and each tracer can be monitored with relative ease using existing data sources such as health records or ones that can be readily set up, including household surveys. But does the list ensure the true health of a population?

Even if all countries made all these interventions available, it would not necessarily mean that people were healthier. The fact that someone is in need of care suggests that they are not healthy, possibly because the system has in some way failed to prevent an illness.

With so many Global Goal targets — the eight MDGs had just 21 — there has been pressure on the UN to reduce the number of indicators. For UHC, one indicator is likely to be concerned with 'affordability', meaning that it is possible that all the chosen interventions, including those mentioned above, will be bundled into a single indicator.

This is a difficult problem. Even the common definition of 'health' as a state free from injury or disease is disputed by some. So it is no surprise that measuring health is fraught with problems. In trying to encompass this complexity, the UN risks creating an indicator that merely measures service coverage of a few selected therapeutic interventions.

Universal coverage is a means towards better health, but is not an end in itself. We should not be measuring health by access to treatments such as nicotine replacement therapy and lung surgery. Instead, we should be looking at tobacco control and other measures aimed at reducing smoking uptake in the first place.

A true indicator of UHC should be an intervention that every country can readily measure, that speaks to equitable access and quality, and that will reliably ensure the health of a population. Immunization is such an indicator. (Some data are missing, but all countries have agreed to work towards measuring vaccination rates.)

That is why some voices, including that of my organization, Gavi, the Vaccine Alliance, are calling for the Global Goals framework to make full childhood immunization a separate ambitious indicator of UHC in its own right.

More than 30 vaccine doses are administered globally every second. No other health intervention reaches so many people, or is capable of preventing such a diverse range of public-health concerns — from virulent infectious diseases such as measles, to cervical and liver cancer. And at the same time, it helps to identify worrying trends in rich countries — such as the drop in immunizations in parts of California to levels on a par with South Sudan, which has led to outbreaks in recent years.

Credit: Oscar Seijkens/GAVI

If immunization is not made a separate indicator, then the UN should make clear that some of the tracers on its long list — including immunization — carry more weight than others. After all, as the old adage goes, when it comes to health, an ounce of prevention is worth a pound of cure.