(CNN) - Between 6.2 million and 7.3 million people in the United States have developed the flu this season, according to data released Friday by the US Centers for Disease Control and Prevention.
This is the first time the agency has provided an in-season estimate of national flu cases.
The CDC also estimates that between 2.9 million and 3.5 million people have seen a doctor because of the flu since the season began in October. Between 69,300 and 83,500 people have been hospitalized because of the virus.
Thirty states have reported widespread flu activity, although flu is present in every state. Fifteen states reported high levels of flu activity as of the week ending January 5. That's four fewer states than the previous week.
The number of children who died of flu increased. Three children's deaths related to the flu were reported in the week ending January 5, bringing the pediatric death toll to 16 for this season, according to the CDC.
Provisional data on how well this season's flu vaccine is working to prevent people from getting sick won't be available for at least several more weeks, according to the CDC.
Last season's flu shot was only 40% effective, and only 37% of adults got vaccinated. The result, experts say: An estimated 80,000 Americans died during last year's remarkably severe flu season, which was the deadliest in more than four decades.
Efforts are underway to create a better vaccine.
Instead of relying on people to get vaccinated every year, scientists are getting closer to a flu vaccine that would last through multiple seasons, called a universal flu vaccine.
"It will be a game-changer," said Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Disease at the National Institutes of Health. "It also would very likely be a much more effective vaccine than the ones we have to make each year, hoping that we guess accurately as to what the influenza virus that season will be."
The National Institutes of Health is investigating several methods to achieve a universal vaccine.
At a congressional hearing on flu preparedness in March, Fauci emphasized the need for a universal flu vaccine and the difficulty in creating one.
For a universal flu vaccine to work, it has to target certain parts of the virus that don't change much from season to season, and that's no easy task.
There's even a possibility it might not work.
"We'll know probably by the end of 2020, the beginning of 2021, whether or not we do have a successful universal flu vaccine," Fauci said.
Until then, Americans will continue to have to keep getting vaccinated every year, which is still better than getting no flu shot at all.
The-CNN-Wire ™ & © 2019 Cable News Network, Inc., a Time Warner Company. All rights reserved.