If there’s a list of the most important inventions in human history, vaccines would easily be on it.

Over the past 50 years, vaccine programs targeting various pathogens, including measles, have saved an estimated 154 million lives across the globe.

That’s one life—most likely that of an infant—saved every 10 seconds.

This achievement relies not only on advancements in vaccine development, but also on the continuous effort to optimise vaccination programs using reliable data.

When someone receives a vaccine, their healthcare provider typically records the details. Governments then aggregate these data, alongside other information about vaccine supply and delivery, to assess the performance of their programs.

In an ideal world, such data helps health leaders make informed decisions to enhance immunisation coverage.

Nevertheless, the pursuit of data-driven decision making also results in an expanding, and almost unmanageable, number of ‘performance indicators’ collected.

“Our recent review identified over 600 distinct indicators being used to measure national immunisation system performance,” says PhD researcher Cyra Patel at the National Centre for Epidemiology and Population Health.

“Countries with constrained systems often have a higher proportion of their immunisation system costs covered by donors and international partners, and thus have greater data reporting responsibilities despite having fewer resources to do this,” notes Patel.

To them, more data may not always be useful.

In a new study published in PLOS Global Public Health, Patel and colleagues asked immunisation experts working in Pacific Island Countries and Territories for their opinions on which indicators matter most to assess the performance of vaccination programs.

Overall, the interviewed experts had strong preferences for data that lead to actions to improve immunisation, that are easier to collect and analyse, and that are collected for fewer indicators.

While all experts agreed some crucial indicators, such as measles vaccination coverage, should be measured, many expressed frustrations over the need to report data that did not provide actionable insights for their specific contexts.

“All stakeholders are interested in the data not just being collected, but actually being used to inform planning,” noted one of the experts working across multiple Pacific Island countries.

In reality, however, some immunisation data were collected simply because they were required for reporting to international agencies.

When resources dedicated to collecting data are diverted away from what matters for the countries, researchers worry that the volume of required indicators might compromise the initial goal of collecting data—to improve vaccination programs.

Complicating the issue is the vast diversity among countries within the region. In the study, Patel also asked experts to choose the most important indicators for countries in the Pacific region.

No consensus was formed.

Although many of the countries face similar challenges, they are still vastly different from one another.

“Participants’ opinions on which indicators were most important in their country were influenced by differences in their health situation, the current performance of their immunisation programs, and the resources available to them,” says Patel.

For example, in countries with lower levels of immunisation coverage, the coverage of vaccines given in the first year of life was seen as a vital indicator. But for those from countries with good data in this area, the coverage of vaccines given to school-age children was deemed more important.

“Differences within the Pacific region mean that it would be inappropriate to have a single set of indicators measuring immunisation performance for all,” Patel says.

The researchers argue that externally imposed demands for data have limited the resources available for measuring indicators that are more informative to decision-makers, which vary from country to country.

“Performance indicators should be country-specific, with countries having the flexibility to set short-, medium-, and long-term goals tailored to their own immunisation needs and contexts,” concludes Patel.