Almost half of UK COVID infections are in people who are at least partly vaccinated, study suggests. But the cases were much milder.

• Almost half of coronavirus cases in the UK were among vaccinated people, per a large UK study.

• The virus seems to be “running out” of people who do not have immunity, the study lead said.

• Hospitalization in the UK could stabilize and likely fall in the UK, he told Insider.

• See more stories on Insider’s business page.

Almost half of COVID-19 cases in the UK are among people who are partly or fully vaccinated people, according to data from a large study.

The finding came from the ZOE COVID Study run by King’s College London. It uses information logged daily by over a million people to predict COVID-19 trends

As of July 15, an estimated 17,581 new daily UK cases of COVID-19 were in unvaccinated people, the study authors said in a press release on Thursday.

That compares to an estimated 15,537 new COVID-19 cases in people who had at least one dose of the vaccine, which is about 47% of all cases.

“That’s probably because the virus is just running out of people to infect who haven’t already been exposed and don’t have natural immune unity in those groups [unvaccinated people],” Prof Tim Spector, an epidemiologist from King’s College London, said in a video accompanying the press release.

Spector is the lead author of the ZOE COVID Study.

People who have had only one dose of the vaccine are less protected against mild symptoms of COVID

COVID-19 is spreading more quickly in those who have received only one dose of vaccines, as can be seen in the graph below from ZOE’s data:

In an email to Insider, Spector said: “Our research showed fewer, milder symptoms were reported in vaccinated people compared to unvaccinated adults who had contracted the virus.”

This aligns with other data suggesting that two doses provide the best protection from the Delta variant, and the one dose gives significantly less, but is better than nothing.

According to figures from Public Health England (PHE), one dose of AstraZeneca or Pfizer vaccine reduced the risk of catching mild symptoms of COVID-19 by 35%.

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However, even one dose of vaccine protects against the more severe risk of COVID-19, reducing the risk of hospitalization by 80%.

Two doses of vaccine were much more protective, reducing the risk of having mild symptoms of the disease by about 80%, and the risk of hospitalization by 96%, the PHE data said.

Preliminary data from ZOE also suggests the risk of long COVID is also substantially reduced by two doses of vaccine, Spector told Insider.

Cases seem to be plateauing in unvaccinated – a good signal

Cases in unvaccinated people were estimated to be 22% lower than the previous week, while cases in vaccinated people rose by 40%. This suggests the wave in the unvaccinated population has now peaked in the UK, the study authors said in the press release.

Hospitalization rates in the UK have risen slightly, with 3,615 new COVID patients in the hospital as of July 14, compared to about 900 in May.

Cases continue to rise driven by the Delta variant. “It is my belief that as more people in the UK receive their second vaccination, hospitalizations will stabilize and likely fall,” Spector told Insider in an email.

Spector told Insider that the figures should be taken with a grain of salt, as there are fewer ZOE app contributors that are now unvaccinated.

“We will monitor cases closely in the next few days in order to confirm the peak.”

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