The contagious Delta variant has become the dominant form of the coronavirus in the United States, now accounting for more than 51% of COVID-19 cases in the country, according to new CDC data to updated on July 6.
The variant, also known as B.1.617.2 and first detected in India, makes up more than 80% of new cases in some Midwestern states, including Iowa, Kansas, and Missouri. Delta also accounts for 74% of cases in Western states such as Colorado and Utah and 59% of cases in Southern states such as Louisiana and Texas.
Communities with low vaccination rates are bearing the brunt of new Delta cases. Public health experts are urging those who are unvaccinated to get a shot to protect themselves and their communities against future surges.
“Right now we have two Americas: the vaccinated and the unvaccinated,” Paul Offit, MD, an infectious disease specialist at Children’s Hospital of Philadelphia, told NPR.
“We’re feeling pretty good right now because it’s the summer,” he said. “But come winter, if we still have a significant percentage of the population that is unvaccinated, we’re going to see this virus surge again.”
So far, COVID-19 vaccines appear to protect people against the Delta variant. But health officials are watching other variants that could evade vaccine protection and lead to major outbreaks this year.
For instance, certain mutations in the Epsilon variant may allow it to evade the immunity from past infections and current COVID-19 vaccines, according to a new study published July 1 in the Science. The variant, also known as B.1.427/B.1.429 and first identified in California, has now been reported in 34 countries and could become widespread in the United States.
Researchers from the University of Washington and clinics in Switzerland tested the variant in blood samples from vaccinated people, as well as those who were previously infected with COVID-19. They found that the neutralizing power was reduced by about 2 to 3½ times.
The research team also visualized the variant and found that three mutations on Epsilon’s spike protein allow the virus to escape certain antibodies and lower the strength of vaccines.
Epsilon “relies on an indirect and unusual neutralization-escape strategy,” they wrote, saying that understanding these escape routes could help scientists track new variants, curb the pandemic, and create booster shots.
In Australia, for instance, public health officials have detected the Lambda variant, which could be more infectious than the Delta variant and resistant to vaccines, according to Sky News.
A hotel quarantine program in New South Wales identified the variant in someone who had returned from travel, the news outlet reported. Also known as C.37, Lambda was named a “variant of interest” by the World Health Organization in June.
Lambda was first identified in Peru in December and now accounts for more than 80% of the country’s cases, according to the Financial Times. It has since been found in 27 countries, including the U.S., U.K., and Germany.
The variant has seven mutations on the spike protein that allow the virus to infect human cells, the news outlet reported. One mutation is like another mutation on the Delta variant, which could make it more contagious.
In a preprint study published July 1, researchers at the University of Chile at Santiago found that Lambda is better able to escape antibodies created by the CoronaVac vaccine made by Sinovac in China. In the paper, which hasn’t yet been peer-reviewed, researchers tested blood samples from local health care workers in Santiago who had received two doses of the vaccine.
“Our data revealed that the spike protein ... carries mutations conferring increased infectivity and the ability to escape from neutralizing antibodies,” they wrote.
The research team urged countries to continue testing for contagious variants, even in areas with high vaccination rates, so scientists can identify mutations quickly and analyze whether new variants can escape vaccines.
“The world has to get its act together,” Saad Omer, PhD, director of the Yale Institute for Global Health, told NPR. “Otherwise yet another, potentially more dangerous, variant could emerge.”
A version of this article first appeared on WebMD.com.