Who dealt best with COVID? The data are in.

Whose pandemic strategy really saved lives? Which states or countries lost the most people to the virus? Or to the unintended consequences of mitigation efforts? Now there's finally some clear, objective data emerging from the fog.

The most telling statistic turns out to be the simplest: all-cause mortality. Tallies of who died, when and where can be used to calculate "excess mortality" — how many more people died in a given place and time period than would be expected. By contrast, official COVID-19 death statistics are clouded by differences in testing and a level of subjectivity doctors say is required to give a cause of death for people who had multiple health problems.

As early as the fall of 2020, statisticians were looking at all-cause mortality to try to figure out whether official COVID-19 deaths were overcounted or undercounted. But today, the death data are more complete, and cover enough time to make revealing comparisons between different periods and regions.

While researchers are still figuring out which factors swayed these death statistics, a few conclusions are becoming clear: First, that COVID has been a global tragedy, causing millions of deaths. Second, that vaccines have saved countless lives. And third, that during the omicron and delta waves, the value of any non-pharmaceutical mitigation measures — masking, distancing, closing businesses and schools — was probably not nothing, but vaccination rates mattered far, far more.

One recently released analysis, not yet peer reviewed, concluded that in the U.S. there were 1.17 million excess deaths from Mar. 1, 2020 to Feb. 28, 2022 — a death rate that's about 20% above the normal number of deaths (5,817,974) for that period. That's higher than the official COVID death count. Excess mortality "is the most agnostic metric because it doesn't ask you to make decisions," said Jeremy Faust, an emergency medicine doctor at Brigham and Women's hospital and co-author of the analysis. "It just asks you to say, are these deaths normal?"

Looking at excess death data has allowed Faust and his collaborators to examine deaths by time period, region, gender, age and race, all broken down into the five or six waves of the pandemic. "We were really looking to say not just how big is this problem, but where is this problem?" he said, "And what does that tell us about our society and how we are responding?"

For example, comparisons made by Faust's team across different counties in Massachusetts showed excess deaths clustered in areas with low vaccination rates. In their nationwide analysis, they found the South had the most excess deaths and the lowest vaccine uptake. (Whether you're comparing counties, states or countries, excess deaths shouldn't depend on factors such as population age or overall health because the statistic compares the actual number of deaths in each region with the typical number of deaths in that same region, said Yale cardiologist Harlan Krumholz, co-author of the preprint.)

Faust and his team was also able to show that Native Americans, Black and Hispanic Americans died in disproportionate numbers, and that men showed more excess deaths than women. And in a surprising twist, while many more elderly people died by sheer numbers, the rate of excess death was higher among people under 50. That is, the death rate among those under 50 was more abnormal than the deaths of those over 65.

Comparing countries can be even more revealing. Another study, published last month in the Journal of the American Medical Association, showed much more excess mortality in the U.S. than was seen in a number of other wealthy countries during the delta and omicron waves.

That study tracked the period after June 2021, when vaccines were widely available in these countries. The U.S. had the most excess deaths, at 145.5 excess deaths per 100,000 people. The next-worst country was Finland with 82.2. The best two were Sweden, with 32.4, and New Zealand, with only 5.1 excess deaths per 100,000.

The 10 most-vaccinated U.S. states appeared comparable to much of Europe at 65.1, while the least-vaccinated states had an excess death rate of 193.3. Numbers like these should help puncture the myth, persistent in some communities, that the vaccines themselves caused a significant number of deaths — that's simply not true.

Some of these rankings and statistics could seed new studies. There's more work to be done to understand why Sweden had fewer excess deaths than any European country studied, and Finland had more. Putting it into context, though, lead author Alyssa Bilinski of Brown University sent me statistics for the pre-vaccine period, where Finland suffered fewer excess deaths than Sweden, which had more lax restrictions than its neighbors. That might mean the restrictions imposed in Finland, but not Sweden, helped before the vaccines, but not afterward, and might suggest Sweden did a better job of quickly getting the vaccines to the most vulnerable.

Vaccination rates were comparable across most European countries, but big differences in excess deaths might hinge on how efficiently these countries got those vaccines into the arms of the most vulnerable, and how well boosters were rolled out during the delta and omicron waves.

The U.S. fared far worse than any of the other countries studied, and New Zealand fared better. New Zealand had the lowest excess death rate before the vaccine rollout as well, and the U.S. came in second worst, next to Italy. Some of those differences may have to do with how badly hospitals were overwhelmed and whether countries were able to do anything to protect nursing home residents, as well as bad luck in getting hit early in 2020.

Bilinski's team also calculated how many U.S. lives would have been saved if we'd done as well as the other countries. There could be 465,747 more Americans alive today if we'd done as well as New Zealand and 375,159 alive if we'd done as well as Sweden.

Of course, there are variables that are hard to control, including the timing of waves — how they coincided with seasonal patterns and waning immunity.

But the parts we can control should become clearer as more scientists study these overall death rates. Right away, it was apparent that the most vaccinated parts of the U.S. had fewer excess deaths.

It would have been impossible for any country to get through the pandemic unscathed, but excess death statistics can show how much better the situation could have been. "This gives you a plausible counter-factual" said Bilinski. She said comparisons can also help focus on successes — whose actions weakened what would have been a category 5 hurricanes to hit as a category 3. Those lessons could save lives in future waves of COVID, or the next pandemic.