On July 19, the United Kingdom eased most pandemic restrictions, rolling back mask mandates and social distancing, once it achieved a high national vaccination rate. But as winter approaches, the U.K. is seeing Covid-19 case rates and hospitalizations rise again, suggesting that herd immunity to the coronavirus may be difficult to reach, Denise Roland reports for the Wall Street Journal.

Your top resources for Covid-19 readiness

UK sees rising Covid-19 case and hospitalization numbers

When the U.K. elected to roll back pandemic restrictions, over half the population had been fully vaccinated, a number that has since risen to 67%. And a survey in July estimated that about 90% of those ages 16 and older had antibodies to the coronavirus, whether from vaccination or a previous natural infection.

During the summer, the country didn't see any significant surges in Covid-19 case rates, but infection rates didn't drop either, Roland reports, floating around 25,000 to 40,000 cases a day.

Now, those case rates are pushing 50,000 per day, with the daily case average hitting around 667 per million, according to data from Oxford University. Comparatively, France and Germany are averaging 80 per million and 147 per million, respectively, and these two countries are utilizing certain public health measures to prevent the spread of the coronavirus.

Meanwhile, hospitalization rates in the U.K. have risen 10% over the past week, Roland reports. Covid-19 death rates have remained much lower than they were last winter—at two per million on average compared with eight per million in January—but that number is still higher than France's 0.47 per million and Germany's 0.82 per million.

Why cases are rising

According to epidemiologists in the U.K., few pandemic restrictions alongside waning vaccine immunity, high numbers of unvaccinated children, more people mixing indoors, and slowing vaccination rates are likely behind the uptick in Covid-19 cases.

Lifting restrictions "was done on the hope that the vaccinations and natural immunity were going to win pretty quickly," said Tim Spector, professor of genetic epidemiology at King's College London. "What it's shown is that that alone doesn't work."

While over 90% of those ages 60 and older have been vaccinated, 70% of those under the age of 35 have been vaccinated, and those younger people are the ones most likely to go to crowded places, meaning they're largely the ones spreading the virus, according to Bill Hanage, associate professor of epidemiology at Harvard University.

The 6 biggest Covid-related myths we've seen, busted

And younger adolescents' movement to get vaccinated has been slow, Roland reports. Fewer than 15% of those under the age of 16 have been vaccinated since the rollout started a month ago.

And while many unvaccinated adults have some natural immunity from previous infections, it's not clear what level of protection natural immunity provides, or for how long.

Meanwhile, immunity among the vaccinated is starting to wane, research shows. One study, which has yet to be peer-reviewed, found that protection against symptomatic Covid-19 dropped to 69.7% for the Pfizer-BioNTech vaccine and to 47.3% for the AstraZeneca vaccine after five months—the two most-used shots in the U.K.

The data show protection from hospitalization has dropped as well, though not as significantly. Protection from severe Covid-19 dropped from 99.7% to 92.7% for the Pfizer vaccine, and from 95.2% to 77% for the AstraZeneca vaccine after five months.

How elusive is herd immunity?

"We're looking at the U.K. and saying: If we achieve those levels [of vaccination] does it really offer that protection that we hope it does?" said Lauren Ancel Meyers, director of the University of Texas Covid-19 Modeling Consortium.

Meyers and other experts say that, while vaccination is significantly improving severe Covid-19 numbers, lower protection against infection means measures like mask-wearing and social distancing may be necessary for short periods of time.

"There's an obligation on those who say we can live with the virus to explain: What does this actually mean?" said Martin McKee, professor of European public health at the London School of Hygiene and Tropical Medicine. "How many deaths are you going to accept?"

Experts say it's possible that some areas, for short periods of time, could reach some level of herd immunity with high enough vaccination rates to lift public health measures, Roland reports. And once cases begin to rise again, other measures like mask-wearing could be used to bring those numbers back down.

"We're not going to get to zero Covid. Or even zero Covid mortality," Hanage said. "But we can get to a degree of burden from Covid which some will consider acceptable." (Roland, Wall Street Journal, 10/21)