On the same day that the world reached the grim milestone of 4 million COVID-19 deaths, World Health Organization chief Tedros Adhanom Ghebreyesus warned that variants are causing a "wave of death" in some parts of the world with less access to vaccines

"Variants are currently winning the race against vaccines because of inequitable vaccine production and distribution," Ghebreyesus said Wednesday at his biweekly conference in Geneva. "It didn’t have to be this way and it doesn’t have to be this way going forward."

Ghebreyesus called on economic leaders of the Group of 20 countries, who are set to meet this week, to work together on getting vaccines and other health tools to less developed countries. 

"Vaccine nationalism, where a handful of nations have taken the lion's share, is morally indefensible," Ghebreyesus said Wednesday. "At this stage in the pandemic, the fact that millions of health and care workers have still not been vaccinated is abhorrent."

Maryland's mobile vaccination clinic was staffed with members of the Maryland National Guard and part of the Maryland Vaccine Equity Task Force, which works with local health departments and community organizations to focus COVID-19 vaccination efforts on "underserved, vulnerable, and hard-to-reach populations."

Maryland's mobile vaccination clinic was staffed with members of the Maryland National Guard and part of the Maryland Vaccine Equity Task Force, which works with local health departments and community organizations to focus COVID-19 vaccination efforts on "underserved, vulnerable, and hard-to-reach populations."

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WHO COVID-19 technical lead Maria Van Kerkhove noted that the Delta variant, which began in India, has now been detected in 104 countries. 

"The Delta variant has even more increased transmissibility than the Alpha variant," Van Kerkhove said Wednesday. "If that virus takes hold, it will spread."

The Delta variant became the dominant strain in the United States on Wednesday, as it is responsible for 51.7% of new cases, according to the CDC. 

In some states, the Delta variant is even more dominant. It's currently responsible for 80% of cases in Utah, which has averaged nearly 400 new cases a day over the past week, almost double the state's case count in early June, deputy director of the state's health department said this week. In Missouri, the Delta variant is responsible for 73.3% of new cases, according to the CDC. 

While the spread of the Delta variant is concerning, the three vaccines that have been approved for emergency use in the United States appear to protect people from it. 

The Biden administration is now moving forward with a new "door-to-door" vaccination drive after it failed to meet its Fourth of July goal of vaccinating 70% of the population. 

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"We need to go community-by-community, neighborhood-by-neighborhood, and oft times door-to-door, literally knocking on doors," Biden said Tuesday of his administration's new vaccination plan, which sparked a backlash from some conservative lawmakers. 

According to the CDC, 67.2% of American adults have received at least one dose of a vaccine and 58.4% are fully vaccinated as of Wednesday.

The Associated Press contributed to this report.