Scientists called achieving collective immunity an even more difficult task.
A new study conducted in the UK has shown that in adults fully vaccinated against COVID-19 who are infected with the Delta variant, the level of coronavirus may correspond to the levels of the virus in unvaccinated people. Scientists say that while the consequences of transmission remain unclear, but it becomes even more difficult to achieve collective immunity.
According to a thorough analysis of data in the UK, which supports the idea that reaching the threshold of collective immunity is unlikely, fully vaccinated adults can have the same high levels of coronavirus as unvaccinated people if they are infected with the Delta variant.
According to The Guardian, there is much evidence that COVID vaccines in the UK still provide significant protection against hospitalizations and death. But a new analysis conducted by scientists shows that, although full vaccination means that the risk of infection becomes lower, after infection with the Delta variant of the coronavirus, a person can have the same levels of the virus as unvaccinated people.
The researchers warn that the implications of this for transmission remain unclear. “We don’t yet know how many cases of transmission can occur from people infected with COVID-19 after vaccination – for example, they may have high levels of the virus for shorter periods of time,” says Sarah Walker, professor of medical statistics and epidemiology at the University of Oxford. – But the very fact that they may have a high level of the virus suggests that people who are not yet vaccinated may not be as protected from the Delta variant as we had hoped.”
Positive tests, hospitalizations, and deaths related to COVID-19 have been slowly increasing in the UK recently. In the week up to August 18, 211238 people had a confirmed positive test result, which is 7.6% more than in the previous seven days.
During the same period, 655 deaths were registered within 28 days after a positive test, which is 7.9% more than in the previous seven days. The number of hospitalizations also increased slightly: 5,623 people were hospitalized with coronavirus in the period from August 8, 2021, to August 14, 2021, which is 4.3% more compared to the previous seven days.
The study, which has yet to be reviewed, showed that the effectiveness of the vaccine against the Delta coronavirus decreased compared to the previously dominant Alpha variant (the so-called “Kent” variant).
The analysis did not directly investigate whether the lower level of protection of the vaccine from the “Delta” variant affects the ability of vaccinations to prevent severe disease. However, Dr. Penny Ward, visiting professor of pharmaceutical medicine at King’s College London, notes: “The low frequency of hospitalizations observed to date suggests that, at least in this respect, vaccines protect people from developing a severe form of COVID.”
The study, conducted by Oxford researchers in partnership with the Office for National Statistics and the Department of Health and Social Security, compared the results of approximately 2.6 million nose and throat swabs taken from more than 384,500 adults between December 2020 and mid-May 2021 and more than 811,600 test results from 358,983 adults in the period from mid-May to August 1, 2021 (the period of “Delta” domination).
The UK’s results on peak levels of the virus after infection with Delta variants in vaccinated people echo the data of a small study mentioned by the U.S. Centers for Disease Control and Prevention (CDC) last month. The agency indicated that these results served as the basis for its decision to recommend that people wear masks in some rooms, regardless of their vaccination status, especially in areas with “significant or high” transmission of the virus.
These data sets to highlight that vaccinated people can still transmit COVID to others and the importance of testing and self-isolation to reduce the risk of transmission, says Dr. Cohen Powels, senior researcher at the Nuffield Department of Population Health at the University of Oxford. In his opinion, this potential of transmission makes achieving collective immunity even more difficult.
The concept of collective or population immunity is based on the fact that the vast majority of the population acquires immunity – either through vaccination or as a result of a previous infection – which, in turn, provides indirect protection against infectious disease for the unvaccinated and those who have never been infected before.
“There was hope that we would be able to vaccinate enough people to protect the unvaccinated,” says Dr. Penny Walker. – I suspect that part of the higher levels of the virus that we see in these [Delta variant-related] infections in vaccinated people is consistent with the fact that unvaccinated people will be at higher risk.”
The researchers also found that compared to the Oxford/AstraZeneca vaccination, two doses of the Pfizer/BioNTech vaccine have about 15% greater initial effectiveness against new infections. Still, protection decreases faster compared to two doses of Oxford/AstraZeneca. As Dr. Walker says, about four to five months after a full vaccination of any vaccines, the protection offered is relatively the same.
“Even with such a slight decrease in protection against all infections and infections with a high viral load, it is important to note that the overall effectiveness is still very high since we started with such a high level of protection,” Dr. Powels says.