The US hasn't vaccinated enough people to stop a Delta variant spike of infections, one of the leading US public-health experts has warned

• A top US public-health expert has warned COVID-19 cases in the US could spike within weeks.
• The US hadn't vaccinated enough people to stop the spread of the highly infectious Delta variant, Dr. Ashish Jha said.
• Jha, dean at the Brown School of Public Health, said that "low vax communities are particularly at risk."

A top US public-health doctor has warned that the nation hasn't vaccinated enough people to stop a spike in cases from the Delta coronavirus virus.

Dr. Ashish Jha, dean at the Brown School of Public Health, said on Twitter on Friday that rising infections in the UK, where vaccination rates are high, suggested the US would not ward off a surge in cases of the more-infectious Delta variant.

Jha predicted a surge in infections over the next few weeks as Delta becomes the dominant strain in the US. "Low vax communities are particularly at risk," he said.

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The Delta variant now accounts for at least 20% of new infections in the US, according to Dr. Anthony Fauci, President Joe Biden's chief medical adviser, who said on Wednesday that the variant was the "greatest threat" to the nation's efforts to eradicate COVID-19. Rochelle Walensky, director at the CDC, said June 18 that Delta would become the most common strain of coronavirus in the US within months.

The Delta variant is spreading especially quickly in kids, who are unvaccinated - but it doesn't appear to be causing more severe COVID-19 than other variants.

Jha explained that in the UK, where Delta has been dominant since June 18, infections had risen five-fold and hospitalizations were up 80% over the past month. This is despite the UK vaccinating more of its population than the US - roughly 54% of Brits are fully vaccinated, according to UK government data, compared with 45% of Americans, per the Center for Disease Control and Prevention (CDC).

Jha added that deaths were low in the UK because "almost all older folks are vaccinated" - about 94% of Brits over 70-years-old are fully vaccinated, according to government data.

-Ashish K. Jha, MD, MPH (@ashishkjha) June 25, 2021

Real-world data from the UK shows that two doses of Pfizer and BioNTech's COVID-19 vaccine offered 88% protection against COVID-19 with symptoms caused by Delta. AstraZeneca's was 60% effective, the data showed.

It's the latest warning from US experts that are using data from the UK to predict what might happen in the US as Delta cases rise.