(CNN) The Covid-19 vaccines have kept more than 18.5 million people in the US out of the hospital and saved more than 3.2 million lives, a new study says -- and that estimate is most likely a conservative one, the researchers say.
The US is nearing the second anniversary of its first Covid-19 vaccinations, and although the coronavirus is still causing thousands of illnesses and deaths, the vaccines have made living with the virus more manageable.
To determine exactly how much the shots have helped, researchers created a computer model of disease transmission that incorporated demographic information, people's risk factors, the dynamics of infection and general information about vaccination. The research comes from the Commonwealth Fund and Yale School of Public Health.
Their study, published Tuesday, found that without Covid-19 vaccines, the nation would have had 1.5 times more infections, 3.8 times more hospitalizations and 4.1 times more deaths than it did between December 2020 and November 2022.
As it stands now, Covid-19 has caused at least 99.2 million cases and more than 1.08 million deaths in the US. Just in the past week, there were 2,981 new deaths and 30,253 new hospital admissions, according to the US Centers for Disease Control and Prevention.
The study estimates that the vaccinations were also a good financial bet, saving the US $1.15 trillion in medical costs.
If you factor in the cases of long Covid that vaccines likely prevented, the savings may be much higher, according to Alison Galvani, one of the study authors.
"Given the emergency of highly transmissible variants and immune-evading variants like Omicron, it is a remarkable success and an extraordinary achievement," said Galvani, founding director of the Yale Center for Infectious Disease Modeling and Analysis.
"Moving forward, an accelerating uptake of the new booster will be fundamental to averting future hospitalization and death."
Nearly 658 million Covid-19 vaccines have been administered in the United States. However, uptake of the new boosters -- which target the original virus strain as well as the Omicron BA.4/5 subvariants -- has been slow since they were authorized this fall. Only about 14% of the eligible population has gotten one, and 1 in 5 people in the US are still completely unvaccinated, according to the CDC.
The Biden administration has been encouraging more Americans to get boosted, especially with holiday gatherings coming up.
"Don't wait. If you wait, you put yourself at risk," Dr. Anthony Fauci, President Biden's chief medical adviser and director of the National Institute of Allergy and Infectious Disease, said Friday at an AARP event. "We're entering the colder months of the late fall and the early winter. We're all going to congregate with our families and friends for the holidays. If you are up to date, great. If you are not, get vaccinated now."
Covid-19 case numbers have been trending upward, as have deaths and hospitalizations, according to the CDC.
About 14% of the US population lives in an area that meets the CDC's criteria for a "high" Covid-19 community level, including New York City, Los Angeles County and Maricopa County, Arizona -- a sharp increase from less than 5% last week but far below levels of prior surges. And at this level, the CDC recommends wearing a mask indoors.
"We are all sick of sickness," AARP CEO Jo Ann Jenkins said Friday. "Each of us has the power to significantly reduce our risk of getting sick."
As numbers trend upward, the experts suggest that masks may be appropriate in some circumstances.
The CDC recommends masking for anyone who's on public transportation. It also suggests wearing one in other public settings in communities where there is a high level of transmission. People who are at high risk of severe illness should wear masks even in areas with only medium community levels.
Other basic prevention measures still apply: Keep hands clean, and stay home if you're sick.