Pfizer vaccine also reduces the risk of asymptomatic infection

It is a strong indication that the vaccine can also prevent many new infections.

In recent months, it has already been extensively demonstrated that the corona vaccines that are currently being used in our country to combat COVID-19, among other things, are safe. And that they greatly reduce the chance of a serious disease course. However, it remained unclear whether these vaccines also reduce the risk of asymptomatic infections. That may not seem very relevant. But appearances can be deceiving. Indeed, studies suggest that a significant proportion of infections are caused by people who have no symptoms. These people do not know they are carrying the virus, do not go into quarantine and can infect quite a few people. In order to limit the spread of the virus as much as possible, you actually need a vaccine that also protects against asymptomatic COVID-19. Pfizer is such a vaccine, researchers are now cautiously concluding this study (which, incidentally, still has to undergo peer review).

The research
The researchers base their conclusions on a survey of British hospital staff. The hospital staff were divided into three groups: a group that had not been vaccinated, a group that had been vaccinated at least 12 days before (the virus is believed to protect against symptomatic COVID-19 after 12 days) and a group that had been vaccinated less than 12 days ago. was vaccinated. Subsequently, all hospital employees involved – despite having no complaints – underwent multiple PCR tests over a two-week period to determine whether they were carrying the virus.

The unvaccinated group underwent 3,252 PCR tests over two weeks, of which 26 were positive (0.8 percent). In the group vaccinated at least 12 days earlier, 1989 tests were conducted, of which 4 (or 0.2 percent) were positive. In the group that had been vaccinated less than 12 days earlier, 3,535 tests were taken during the same period, of which 13 were positive (0.37 percent). The results cautiously indicate that the risk of asymptomatic infections among hospital staff vaccinated at least 12 days earlier is four times lower. And for hospital staff vaccinated less than 12 days ago, the risk of asymptomatic infections has been halved.

Promising news
“This is great news – the Pfizer vaccine not only protects against SARS-CoV-2 disease, but also helps prevent infection, thus reducing the chance of the virus being passed on to others,” said researcher Mike Weekes. “This news is very welcome as we try to map out a route out of this pandemic. But we must keep in mind that the vaccine does not provide complete protection for everyone. So we still have to keep our distance, wear face masks, wash our hands and get tested regularly until the pandemic is better under control. ”

The research is in line with a study which appeared earlier this week and was based on research in Israel. The study not only found that the Pfizer vaccine protects against COVID-19, but also showed that the vaccine also protected against asymptomatic infection, especially after a second administration. In this new research, however, scientists show that the vaccine does this even after one dose. “These studies are very promising because they suggest that vaccines prevent the spread of the virus,” concludes Professor Lawrence Young, of Warwick Medical School and not involved in either study.

Professor Jonathan Ball, a molecular virologist at the University of Nottingham and not involved in the study among British hospital staff, is also enthusiastic. “Such a reduction in infections after a single dose of the Pfizer vaccine is very impressive and shows that vaccinations are really a way out of current limitations and into a much brighter future.”

Follow-up research
At the same time, more research is desperately needed, most experts agree. The British study is not very extensive and, moreover, only concerns hospital staff. Many hospital employees have previously been exposed to corona and therefore had an immune response prior to vaccination that may have enhanced the effect of the vaccine. It therefore seems good to repeat the study among a larger and more diverse group of people in the future, argues Dr. Simon Clarke, cellular microbiologist at the University of Reading and not involved in the study. “In addition, it is also important to remember that these results cannot be directly translated to other vaccines.” They only apply to Pfizer. Furthermore, even in the case of the Pfizer vaccine, it remains unclear how long protection against (a) symptomatic infection will last.

But in anticipation of that follow-up research, we can certainly have high hopes based on this preliminary study. Hope that vaccines will actually make a difference. “These preliminary data are not sufficient to ensure that vaccinations prevent infection and transmission – and thus contribute to herd immunity – but they strongly suggest that it is,” said Dr. Peter English, former chairman of British Medical Association Public Health Medicine Committee and also not involved in the study. “And that gives us the hope that vaccinations will – ultimately – ensure that there is less or even no need for social distancing, mouth masks and other behavioral measures.”

If the results also remain valid during follow-up studies, vaccinations will indeed lead to a significant decrease in virus transmission and thus new infections. It’s great news. But it does require people to get vaccinated, says Dr. Andrew Freedman of Cardiff University School of Medicine. “The (study, ed.) Emphasizes the importance of everyone being offered the vaccine accepting it in order to protect themselves as well as others in the community.”

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