Covid-related hospitalizations and deaths were relatively low, even if cases continued to rise, and the country's vaccination rollout was largely lauded as a success internationally.

But now, there are fears that the immunity gained from Covid vaccinations is starting to wane as the delta variant — which has accounted for approximately 99.8 percent of sequenced cases in England, according to a recent government report — as well as a mutation of the variant known as "delta plus" continue to spread2

"We all assumed that these vaccines would be good and keep us safe for a good year or two, and that possibly would have been true if delta hadn't come along," he said.

Yet, even with the spread of the delta variant, he said the rollout of booster jabs in the U.K.

Deepti Gurdasani, a clinical epidemiologist at Queen Mary University of London, said she also believed the rollout of the U.K.'s vaccination program, as well as its slow release of booster vaccines, have played a role in the continued rise of Covid cases.

government's decision to not maintain or reinstate certain Covid containment measures, such as masks being mandatory in enclosed spaces, were also behind the rise, Gurdasani said.

While many countries across Europe and around the world have maintained different levels of Covid restrictions, including mask mandates, the British government has remained adamant in its commitment to England’s full reopening.

Ravi Gupta of the Cambridge Institute of Therapeutic Immunology and Infectious Disease agreed with Gurdasani that maintaining restrictions might have helped avoid the U.K.'s current predicament.

"The relaxation [of rules] that happened over summer was a fairly drastic month going from, you know, quite, quite tight measures to very few restrictions," Gupta said.

The emergences of the delta and then the so-called delta plus variant have garnered attention and produced some fear.

But Gurdasani and Gupta agreed that the arrival of the delta plus variant, which is a mutated version of the delta variant, shouldn't come as much of a surprise.

15 warning the delta plus variant appeared to be "expanding," it accounted for around 6 percent of Covid cases in the U.K.

Gurdasani said at the moment, it does not appear to be the main driver of the rise in Covid cases.

Ultimately, Altmann said it would be "foolhardy" to try to blame the rise in Covid cases and deaths in the U.K.

The government of Prime Minister Boris Johnson is coming under growing pressure to reimpose restrictions in light of the surging cases and deaths.

Rather than imposing new restrictions, Javid warned that Britons must all "play our part" and focus on getting vaccinated, including with Covid boosters and flu jabs, to avoid the return of coronavirus rules

If the country does not change its approach, Gurdasani said she expected those numbers only to rise in the months ahead