• The number of Covid cases being recorded daily in the West remains high, and even resembles earlier peaks at different points, or Covid waves, during the pandemic.
• The high numbers of cases remains attributable to the spread of the highly infectious delta variant, which usurped previous variants that themselves were more infectious than the original strain of Covid-19.

LONDON — Looking at the Covid case data in the U.S., U.K. and the rest of Europe, you'd be forgiven for thinking that, despite 18 months of a global health crisis and advanced vaccination rollouts, we're in just as bad a situation as we ever were.

Certainly the number of Covid cases being recorded daily in the West remains high, and even resembles earlier peaks at different points, or Covid waves, during the pandemic.

The current 7-day moving average of daily new cases stands at 153,246, an increase of 4.9% compared with the previous 7-day moving average (of 146,087). The current 7-day moving average is 123.6% higher than the value observed around a year ago, according to data compiled by the Centers for Disease Control and Prevention (CDC). In total, more than 40 million Covid cases have been counted in the U.S. since the pandemic began.

Case rates in the U.K. also remain high. As of Sept 6., the seven-day average of daily new cases was almost 39,000 and the number of daily cases has remained high as the week has progressed; almost 40,000 new cases were reported on Wednesday, and around 38,000 cases were recorded on Thursday, government data showed.

In the EU + EEA area (a total of 30 countries), in the seven days up to Sept. 5, 405,774 new cases were recorded, according to the European Centre for Disease Prevention and Control, with Ireland, France, Sweden, Portugal, Greece and Bulgaria among the countries reporting the highest numbers of new cases per 100,000 population.

The high numbers of cases remains attributable to the spread of the highly infectious delta variant, which usurped previous variants that themselves were more infectious than the original strain of Covid-19.

Nonetheless, the rise in cases has accompanied the advancement of vaccination programs in the West with the majority of adults in both the U.S. and Europe now fully vaccinated.

In the U.S., 62.4% of all people over 12 years of age are fully vaccinated, CDC data shows, while over 82% of over-65s are fully protected. In the U.K., 80.4% of the population over the age of 16 are fully vaccinated and in the EU/EEA, 70.4% of adults have received two doses of a coronavirus vaccine, ECDC data shows.

Crucially, the number of hospitalizations and deaths accompanying the high number of cases has remained lower (and for some countries, much lower) than at earlier points in the pandemic when vaccination rates were much lower, proving that the coronavirus vaccines in use in the West dramatically lower the chance of a severe infection, hospitalization and death. Hospitalizations in the U.S. remain high, data from Our World in Data show.

Yet none of the vaccines in use in the U.S. or Europe is 100% effective, meaning that some vaccinated people will get Covid (so-called "breakthrough cases") and a small number of those will get sick. The predominant delta variant has also lowered the efficacy of the vaccines on offer and some new studies show the immunity provided by shots wanes over time.

Why are cases high?

CNBC asked epidemiologists based in Britain why cases remain so high given the relatively high vaccination rates in the West.

"The delta variant is highly contagious and this accounts for the continuing high number of cases now that we are mixing much more freely since most restrictions were eased," Andrew Freedman, a reader in infectious disease at Cardiff University School of Medicine, told CNBC Thursday.

"Those catching Covid now are a mixture of unvaccinated, partially vaccinated and double vaccinated people. A large proportion of new infection are in (unvaccinated) children and adolescents," he noted.

"We know that the vaccines are only partially effective at preventing people from catching the delta variant, but are much more effective at protecting against severe disease, hospitalisation and death.  Fully vaccinated individuals are mostly getting only mild symptoms if they do catch it, although a small minority, especially older and more frail people, are still getting more severe illness."

In the U.K., the latest data from the ZOE Covid study, which tracks Covid symptoms and infections in the community using the data from around a million people every week, estimates that in the fully vaccinated population, there are currently 17,674 new daily symptomatic cases in the U.K.

It noted, in its latest research published on Thursday, that "cases in this group had been rising steadily but have now stabilised, with last week's figure being 17,342."

Meanwhile, new Covid cases are the highest among those aged 0-18 and 18-35 year olds, many of whom are only partially vaccinated (two doses of a Covid shot are vital to achieve maximum protection), or unvaccinated.

Similar data pertains to the U.S. and the rest of Europe over the last month: CDC data shows that the highest number of cases has been counted among adolescents aged 16-17 (though age groups from 12-49 have all seen a sharp increase in cases). In the EU/EEA the highest number of cases is among the 25-49 year old age bracket closely followed by the 15-24s and a rising number of cases among children, age 5-14.

Epidemiologists and public health experts have long-expressed the view that Covid-19 is just something we're going to have to get used to, that the virus will become endemic and cannot now be eradicated.

Pursuing a so-called "zero Covid" strategy (aiming to eliminate all Covid cases) has been seen as a hopeless cause by most countries, although Australia and New Zealand have pursued such a strategy. Australia announced at the end of August that it was abandoning such a policy, however, given the spread of the highly infectious delta variant. New Zealand is maintaining its strategy, for now.

Danny Altmann, professor of immunology at Imperial College London, explained to CNBC that societies need to assess to what extent they will tolerate the virus.

"We've always said, and still maintain, that the vaccines are amazing and give enormous levels of protective neutralising antibodies," he told CNBC Thursday. Even if clinical studies show that the delta variant reduces the efficacy of vaccines, Altmann noted "there's so much protective headroom that 'most' people should be safe."

"In a sense that's how we've seen it play out — with the delta variant and without vaccination we'd now be at several thousand deaths per day, but we're at 'only' a few hundred, so there's tangible mitigation of severe disease," he said.

"However, our protection seems less robust against delta than we'd predicted when you consider that in the U.K. there are around 40,000 cases per day including many of these breakthroughs ... [and] people becoming significantly unwell though not hospitalised," he said, noting that data from Israel on giving booster shots showed that additional jabs could re-boost antibody levels and combat breakthrough cases.

A lot of the debate around Covid currently, Altmann said, "comes back to that policy/philosophy debate about what we're now trying to achieve."

"The extremes of the argument are, either that, at least until we see what happens in autumn/winter, we've achieved our goal as relatively high vaccine rollout has meant that hospitals can just about cope ... Or, the other view is that we'll never have normality unless we strive for a zero-Covid strategy, which would need to encompass vaccination in our schools to stop spread there," he noted.

Those calling for a zero-Covid strategy encompassed people who believed that "we're sitting ducks in perpetuity for ever more cases, until we allow through a much more resistant variant to really scupper us," Altmann said.