United Kingdom residents have been warned that a sharp rise in the nation's COVID-19 infections and deaths has begun.

The spike, which Public Health England says will become even more pronounced after millions of students return to universities, schools, and colleges in September, is likely to continue for several months.

The Financial Times quoted experts as saying the return to the confines of the classroom, coupled with an anticipated reopening of some offices, and a seasonal dip in temperatures that will cause an increase in indoor socializing will all contribute to the resurgence of the novel coronavirus.

Public Health England, which is known as PHE and which is part of the government's Department of Health and Social Care, said UK deaths from COVID-19 now average 100 a day, which is the worst rate seen since mid-March. Throughout much of May and June, the UK daily deaths were recorded in single figures.

Ravi Gupta, a professor at the University of Cambridge and a member of the New and Emerging Respiratory Virus Threats Advisory Group, told The Guardian newspaper things could get a lot worse in the coming weeks.

"There is nothing to stop it happening because … there are still a lot of people who have not been infected with (the) Delta (variant) and who will get infected, and some of them will become more ill than others," he told the paper. "So, I think there is still a way to go with this. And yes, it is going to coincide with schools reopening, and of course you have waning immunity as well."

"Waning immunity" refers to the fact that many people who were jabbed during the early days of the UK's vaccination program-including the very elderly and those described as clinically extremely vulnerable-may no longer be fully protected by vaccines because it is unclear how long they can be expected to remain effective.

PHE said this week confirmed new COVID-19 infections, which were few during July, now number around 32,000. It said the number of daily infections is now 13 percent higher than a week earlier. Similarly, while there were 672 people in hospital in England on July 31 because of COVID-19, there were 948 on Aug 17.

The BBC noted that COVID-19, which dropped to 26th place in the ranking of the causes of deaths in England during June, rose to ninth place in July and is set to rise again. The disease was top of the ranking in England during April, May, November, and December of 2020, and throughout January and February of this year.

With COVID-19 resurgent and predicted to become an even bigger problem in the coming weeks, the British government has ordered another 35 million doses of the Pfizer-BioNTech vaccine, for delivery during the second half of 2022.

The jabs will be used as part of the nation's booster program.

Health Secretary Sajid Javid said this week the UK is working to "future-proof" its vaccine program and will roll out this year's booster program in September, initially for the elderly and for people who are clinically extremely vulnerable.

"While we continue to build this wall of defense from COVID-19, it's also vital we do everything we can to protect the country for the future too, whether that's from the virus as we know it or new variants," the broadcaster quoted him as saying.