Covid-19 was the third leading cause of death in the U.S. last year, with only heart disease and cancer killing more people, according to data released Friday by the Centers for Disease Control and Prevention.Covid killed more than 415,000 people in 2021 and contributed to the deaths of 45,000 more people, about 20% more than the first year of the pandemic, when the virus was involved in the deaths of more than 384,000 people.The CDC data, based on death records among U.S. residents from January through December 2021, is provisional and subject to change as more information is reported.People 85 and older had a higher death rate from Covid than any other age group, and more men died from the virus than women. The death rate was the highest for American Indians when adjusted for age and population. Hispanics, Black people and Pacific Islanders also had higher death rates from Covid than white people. Asians and multiracial individuals had the lowest death rates.Only heart disease and cancer killed more people than Covid in 2021, taking the lives of about 693,000 and 604,000 people, respectively. Unintentional injuries were the fourth leading cause of death, killing more than 219,000 people.Though the U.S. began rolling out the vaccines in early 2021, many people did not and still have not gotten their shots. The delta variant also swept the nation in 2021, causing more severe illness than other Covid variants, according to the CDC.As of Thursday, 34% of the U.S. population was not fully vaccinated and about 23% of the population had not received a single dose. The only age group not yet eligible for vaccination is children under the age of 5 years old.Unvaccinated people ages 12 and older were 20 times more likely to die from Covid and three times more likely to test positive for the virus than people who had received three doses of the vaccine, according to data presented at a CDC advisory committee meeting Wednesday.More than 987,000 people have died from Covid in the U.S. since the pandemic began, according to CDC data. Though deaths from Covid have dropped 85% from the peak of the winter omicron wave, about 375 people are still dying every day from the virus on average, according to the data.In the optimistic scenario, about 96,000 people could die of Covid from March of this year through March 2023, according to the Covid-19 Scenario Modeling Hub, a group of scientists at several top universities and medical institutions including Penn State, Johns Hopkins and the National Institutes of Health.In the most pessimistic scenario, 211,000 people could die from the virus over the next year if current immunity in the population wanes quickly and a Covid variant emerges that is able to escape immune protection from the vaccines and previous infections, according to the scientists. The methods that the Covid-19 Scenario Modeling Hub uses to make projections were developed in consultation with the CDC.