(WHTM) — There have been almost 100,000 more deaths attributed to COVID-19 in 2021 than there were in 2020. While COVID-19 vaccines have been going into arms in the U.S. for the entirety of 2021, health experts say the rising death toll doesn’t mean the vaccines aren’t working.

The first coronavirus vaccine in the U.S. was given just over one year ago on Dec. 14, 2020, and health experts lauded its ability to curb the spread of the virus. They say that although the U.S. death toll associated with COVID-19 has been greater in 2021 than it was in 2020, the vaccines are still doing their job.

“Among the people who have had the vaccination, the deaths have gone way down,” said Dr. John Goldman, infectious disease specialist at UPMC. “What we’re seeing is hospitalizations and deaths among people who have not had the vaccination.”

Goldman said cases at UPMC in Central Pennsylvania are going up, but less than 10% of the people in those hospitals are vaccinated, with the average number of vaccinated COVID patients hovering around 10-20%.

“If we had everyone vaccinated, we would only have 20 people in our hospital, not 200,” he noted. Goldman added that among patients with more severe disease — those in ICUs or on ventilators — usually only 5-10% are vaccinated.

Other hospitals in Central Pennsylvania, like Penn Medicine Lancaster General Health, report similar statistics:

So if the vaccines are successful at helping prevent COVID-19 cases, severe disease, and death, why have there been more deaths associated with COVID-19 in 2021 after the vaccines became available in the United States? Goldman says there are several factors that have contributed.

First, Goldman pointed out, the vaccines didn’t become widely available to all Americans until April, several months into 2021. It took until August for half of the U.S. population to be fully vaccinated.

In fact, Goldman said, people in the groups that were first to become eligible for vaccines and people in the groups with the highest vaccination rates now account for fewer COVID-19 cases and deaths.

“In early 2020, the average patient with COVID was probably an elderly, often very medically ill nursing home patient, and now, the average patient with COVID is an unvaccinated 40- to 50- to 65-year-old,” Goldman said.

More infectious coronavirus variants also contributed to the greater death toll in 2021, Goldman explained.

The alpha variant, which started spreading in the U.S. in the spring of 2021, was about 50% more contagious than the ancestral strain, Goldman said, and then the delta variant came along and was about 50% more infective than the alpha strain.

"As the virus became more infectious, became more contagious, we saw more people get infected. Even though there's a smaller susceptible population...if the virus is four times more infectious, it still spreads more quickly," Goldman said.

With more people getting infected, more people wound up in the hospital with COVID-19, and more people died from the virus -- even though methods for treating it have improved since the start of the pandemic.

"We're continuing to see cases, and even though we're much better at treating it, because the virus is more infectious, more contagious, because we're seeing more cases, even though your chances of dying if you get COVID have gone down, they're still substantial, they're still there, and when you have more cases, you have more deaths," Goldman said.

On top of the coronavirus variants and the virus' spread before vaccines were widely distributed in the country, lockdowns and COVID-19 mitigation efforts followed more strictly in 2020 loosened in 2021.

"When we say that more people have died despite the vaccines...first of all, many more people had COVID in 2021 than in 2020. And for a good portion of 2021, we didn't have most of the population vaccinated. And we are almost exclusively seeing the hospitalizations and deaths among the unvaccinated," Goldman reiterated.