More people died of COVID-19 than we know. Or ever will know. Because data is missing.

Nature reports on the gaps in information that mean the official counts of people who died as a result of COVID-19 are much, much lower than the real numbers:

The [Nature and WHO] data suggest that during 2020 and 2021, excess mortality was some 2.7 times greater than the official toll, at between 13.2 million and 16.6 million deaths, with the most-likely value 14.8 million.

This is, in fact, slightly more conservative than other estimates. In March, the Institute for Health Metrics and Evaluation (IHME), a global health-research centre at the University of Washington in Seattle, reported a range of 17.1 million to 19.6 million excess deaths between 1 January 2020 and 31 December 2021, with a most-likely figure of 18.2 million. A team at The Economist magazine uses a machine-learning model to produce a constantly updated figure that was originally around 18 million, but currently lies at around 16 million (see go.nature.com/3d5bpc3).

irst, it emphasizes the scale of the crisis, and highlights that many low- and middle-income countries that on the face of it saw few deaths were probably hit just as hard as richer countries, if not more so. People in these countries did not enjoy a secret immunity to COVID‑19, even if their deaths were not recorded as assiduously as were those in higher-income nations.

Second, it underlines how much still needs to be done to improve systems for recording deaths. The United Nations is trying to track countries’ success in registering deaths as part of its Sustainable Development Goals. Its latest records state that by 2020, 154 countries out of 188 tracked had death data that were “at least 75% complete”. In countries with weak social safety nets, there might be little incentive for people to report deaths. When asked, many people say they didn’t know they needed to. Census-type surveys can fill in some gaps later, but tend to focus on capturing maternal and child mortality. The UN children’s charity UNICEF estimates that, globally, around half of all deaths are not officially counted; a non-profit public-health organization in New York City called Vital Strategies more optimistically suggests that 40% are unregistered.