NEW YORK - The US federal government is doubling down on COVID-19 vaccination efforts, including an ongoing plan for booster shots, while more unvaccinated people fell victims to the Delta variant in recent weeks, and the pandemic is believed by health experts to become a routine illness in the United States.

A surge in COVID-19 deaths caused by the highly contagious Delta variant is hitting working-age people hard while highlighting the risks for people who remain unvaccinated, reported The Wall Street Journal (WSJ) on Monday.

Federal data showed that COVID-19 deaths among people under 55 have roughly matched highs near 1,800 a week set during last winter's surge. These data showed weekly tallies for overall COVID-19 deaths, meanwhile, remain well under half of the pandemic peak near 26,000 reached in January.

The seven-day average for newly reported COVID-19 deaths each day recently eclipsed 1,600, up from an average that briefly moved below 220 a day in early July. With roughly 660,000 known COVID-19 deaths to date, the United States is on track to "soon top the estimated 675,000 deaths that the Centers for Disease Control and Prevention (CDC) has linked to the 1918-19 flu pandemic", said the report.

High vaccination rates among the elderly, who are more vulnerable to severe COVID-19 outcomes, are restraining the overall increase in deaths, and the change is shifting a larger share of deaths to younger populations with lower vaccination rates, underscoring the need to get more people inoculated to curb the pandemic, WSJ quoted experts as saying.

Deaths have been concentrated among the unvaccinated, federal data show. The CDC released studies on Friday showing that unvaccinated Americans were 4.6 times as likely to be infected, 10 times as likely to be hospitalized and 11 times as likely to die.

COVID-19 may become a routine illness like a common cold or the flu one day, another WSJ report on Monday quoted virologists and epidemiologists as saying. But it will take a lot to get there, and the ferocious spread of the Delta variant that has filled hospitals again showed how challenging that path could be.

"While surges are easing in some states, cases are rising in others. Delta is moving the world toward immunity against the virus at huge cost. With every new infection it is raising the risk of incubating a variant that might spread even faster, sicken with greater ferocity or evade vaccines," said the report.

Scientists are trying to figure out whether SARS-CoV-2 will form deadlier or more contagious new variants, and how the pandemic might end. Their best-case scenario isn't anything as hopeful as eradication.

"Instead, many expect COVID-19 will become a routine disease like a common cold or the flu, rather than a cause of mass hospitalizations and deaths," said the report.

When or even whether COVID-19 settles into that status depends on how many more people get vaccinated and how soon, Adolfo Garcia-Sastre, director of the Global Health and Emerging Pathogens Institute at the Icahn School of Medicine at Mount Sinai in New York, was quoted as saying.

Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, told CNN on Sunday if more people aren't persuaded to get vaccinated by messaging from health officials and "trusted political messengers," additional mandates from schools and businesses may be necessary.

"I believe that's going to turn this around because I don't think people are going to want to not go to work or not go to college ... They're going to do it," said Fauci. "You'd like to have them do it on a totally voluntary basis, but if that doesn't work, you've got to go to the alternatives."

In related development, COVID-19 vaccine boosters could begin to be available in a week to all fully vaccinated Americans, but exactly who will be eligible and when won't be decided until two key scientific advisory committees meet days before the US administration's Sept. 20 start date, reported USA Today on Monday.

Originally, US President Joe Biden said a third shot booster dose for people with healthy immune systems would be offered beginning Sept 20 to anyone who'd gotten their second shot of either the Pfizer-BioNTech or Moderna vaccine at least eight months ago, pending authorization from the Food and Drug Administration.

Of the eligible population in the United States, which is currently limited to people 12 and older, 63 percent are fully vaccinated, according to data from the CDC.