COVID-19 is now the second-leading cause of death in the United States, despite the availability of safe, effective, and free vaccines. The promise of those vaccines showed itself when they first became widely available and COVID-19 dropped to be seventh on the list of causes of death. Then came the delta variant, and the levels of vaccination in the U.S. were not enough.

That proved deadly: A new study concludes that 90,000 deaths could have been avoided over a period of four months, from June through September, if more people had gotten vaccinated.

COVID-19 was the top cause of death in the U.S. for a period in late 2020 and early 2021, beating out the usual reliable No. 1 of heart disease. But by June, COVID-19 had dropped below cancer, accidents, stroke, and other respiratory illnesses—down by Alzheimer’s. Not anymore.

In September, according to the estimate released by the Peterson Center on Healthcare and the Kaiser Family Foundation, COVID-19 was the top cause of death for people aged 35 to 54, […]