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Can people who have received the SARS-CoV-2 vaccine infect others? This question has been being asked for months, especially since the appearance of the more contagious Delta mutation. There are more studies on the subject – this time from the University of Oxford. “This is the highest-quality study we have conducted so far on the infectivity of vaccinated Delta-infected people,” said Dr. Aaron Richterman from the University of Pennsylvania. What have the scientists discovered?
- British scientists investigated how the COVID-19 vaccines from Pfizer-BioNTech and AstraZeneca affect the spread of SARS-CoV-2 in the event of a breakthrough infection
- People vaccinated against COVID-19 are less likely to spread the virus, even if they develop a breakthrough infection
- Both vaccines reduced pathogen transmission, although they were more effective with the Alpha variant than with the Delta mutation
- Scientists emphasize that it is still important to wear face masks and test
- You can find more important ones on the Onet homepage.
Those vaccinated against COVID-19 can infect. «Top-quality research»
Before we present the findings from the University of Oxford, let us recall why COVID-19 infections may occur among vaccinated people. Vaccination is all about preventing severe disease and complications, including death. So it may happen that we get sick after receiving the vaccine. However, the vast majority of these cases will be mild (including asymptomatic). – As long as such diseases are not dangerous for an infected person, such a person, even if he is infected asymptomatically, can infect others – said Dr. Lidia Stopyra, a specialist in infectious diseases in the spring. (more in the article: COVID-19 despite the vaccine. When can it happen, is it dangerous? explains the doctor).
Even in the summer, there were opinions that transmission of the coronavirus by fully vaccinated people was not impossible, but unlikely thanks to the vaccine. – In virology, the hallmark of transmission is the viral load. The more you have, the more likely it is to spread, said Dr. Bruce K. Patterson, virologist and CEO of IncellDx, a company that develops new methods for predicting, identifying and treating the long-term effects of COVID-19 (more on this).
How do vaccines affect the spread of the coronavirus in the event of a breakthrough infection (i.e. following vaccination)? Scientists from the University of Oxford were looking for an answer to this question.
People who are fully vaccinated against COVID-19 are still at risk of becoming infected with the coronavirus – there is no vaccine that is 100% vaccinated. effectiveness (and this does not apply only to preparations against SARS-COV-2). Scientists describe these types of infections as “breakthrough”, “breakthrough”.
The study, which was released on September 30, has yet to be reviewed, but scientists unrelated to the project say the findings are plausible. – This is the highest-quality study we have conducted so far on the infectivity of vaccinated Delta-infected individuals Says Dr. Aaron Richterman, an infectious disease physician at the University of Pennsylvania. Susan Butler-Wu, a microbiologist at the University of Southern California, emphasizes that the study mirrors transmission not in an artificial environment, but in the real world.
To what extent can the vaccinated infect? The research results
British scientists analyzed the national registers of nearly 150. contacts that have been traced from around 100 initial cases of COVID-19 infections. These included people who had been fully or partially vaccinated with Pfizer-BioNTech or AstraZeneca, as well as those who had not been vaccinated. The researchers then looked at how vaccines affected the spread of the virus if a person had a breakthrough infection with the Alpha variant or the more contagious Delta variant.
Greater infectivity of the Delta mutation meansthat much less virus is needed to induce symptoms than was the case in the previous variants.
Both analyzed vaccines reduced transmission, although they were more effective against the Alpha variant than the Delta mutation. After contamination with the Delta variant, the contact in question was 65 percent. less ‘susceptible’ to a positive test if the person who caught the infection had been vaccinated with two doses of the Pfizer vaccine. In the case of AstraZeneka, the probability of a positive test result for a given contact was 36%. smaller if the exposed person has been fully vaccinated against COVID-19. The risk of transmission of the pathogen was much higher if an individual took only one dose of any of the vaccines included in the study.
Why do COVID-19 vaccines infect less frequently? How long does protection last?
An earlier study from Singapore found that SARS-CoV-2 levels were initially the same in people infected with the Delta variant, regardless of vaccination status. By the seventh day, however, they decreased rapidly in the vaccinated. Scientists believe that Vaccinated people are likely to clear the infectious virus from the body more quickly. ‘The immune system of people who have been vaccinated can fight the virus with antibodies much faster than unvaccinated people who need to build up an immune response,’ explained Dr. Aaron Richterman.
The new study also suggested that protection against coronavirus transmission appeared to weaken over time. After three months, people who had breakthrough infections after being vaccinated with AstraZeneka had the same likelihood of spreading the Delta variant as unvaccinated people. While protection against transmission was also reduced in those who received the Pfizer vaccine, there was still a benefit compared to unvaccinated people.
“We know that the number of circulating antibodies in the blood decreases over time after vaccination, even though the immune memory remains persistently strong and is still able to prevent infections, especially severe infections,” said Dr. Richterman. The researcher also noted that “circulating antibodies, which are immediately available, probably play a role in preventing the pathogen from transmitting in the event of an infection”. “So I don’t think we’ll see a diminished transmission protection over time.
Do you want to test your COVID-19 immunity after vaccination? Have you been infected and want to check your antibody levels? See the COVID-19 immunity test package, which you will perform at Diagnostics network points.
Both Dr. Richterman and Susan Butler-Wu emphasize the importance of wearing face masks and testing. “To reduce the amount of virus we are exposed to, we need to combine vaccines with other measures, such as mask application and testing,” emphasizes the microbiologist. Aaron Richterman agreed with her.
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