Washington, Jul 13 (IANS): Covid-19 cases rose in more than 40 US states over the past week as the vaccination rate has slowed down and the highly transmissible Delta variant continues to spread.

The country is averaging about 19,455 new cases over the last seven days, a 47 per cent increase from the week prior, according to data from Johns Hopkins University, Xinhua reported.

It marked the largest weekly rise since April 2020, according to a Bloomberg report.

More than 99 per cent of COVID-19 deaths in the United States in June were among unvaccinated people, said Rochelle Walensky, director of the US Centers for Disease Control and Prevention (CDC).

In addition, preliminary data indicates that over the past six months, nearly all of the COVID-19 deaths in various states have occurred in unvaccinated people, she said.

The pace of vaccinations has also dropped in the country sharply in the past few months. About 246,000 people initiated vaccination each day over the past week, down 88 per cent from the April peak, and about 278,000 people became fully vaccinated each day over the past week, down 84 per cent from the April peak, CDC data show.

About 48 per cent of the US population is fully vaccinated against COVID-19, and 55.5 percent of the population has received at least one shot as of Sunday, according to CDC data.

Experts have said COVID-19 vaccines are key to managing spread and prevent variants from mutating into even more dangerous forms.

"We really need to get more people vaccinated, because that's the solution," said Anthony Fauci, White House chief medical advisor, on Monday. "This virus will, in fact, be protected against by the vaccine."