Booster effect according to the study: people who have been vaccinated three times are less contagious with Omikron

Created: 04/12/2022, 17:25

A woman is vaccinated against Corona during a vaccination campaign.

© Daniel Bockwoldt/dpa/symbol image

Infection with the omicron variant is usually milder.

Vaccinated with a booster are apparently less contagious than unvaccinated.

Geneva – The corona virus is changing.

Omicron is now circulating after Delta.

A corona vaccination does not offer 100 percent protection against infection.

A booster shortens the duration of symptoms in Omikron, as a British study recently showed.

Corona vaccinated are also less contagious.

However, vaccination status makes a difference in omicron infection.

Unlike the Delta variant, however, three vaccine doses are required for the Omicron variant in order to effectively reduce the amount of infectious virus particles.

This is what Swiss researchers working with Isabella Eckerle and Benjamin Meyer from the University of Geneva report in the journal

.

The study refers to the

, not to the omicron subvariant BA.2, which is meanwhile dominant in Germany.

"Our results underline the positive effect of vaccinations that go beyond individual protection against serious illnesses," conclude the researchers.

"The vaccination can reduce the infectious viral load, which probably leads to less further transmission," emphasizes the virologist Isabella Eckerle on Twitter.

Between April 2020 and February 2022, the research team took swabs from the nasal mucosa of a total of 565 people infected with corona within the first five days after the onset of symptoms.

The investigation thus covers almost the entire course of the pandemic to date: infections with the originally circulating variant as well as with the delta and omicron variants were recorded.

Some of the subjects were not vaccinated, others were vaccinated twice or boosted.

Almost all vaccinated had received an RNA vaccine.

• The study “Infectious viral load in unvaccinated and vaccinated individuals infected with ancestral, Delta or Omicron SARS-CoV-2” was published in the journal

  Nature

  on April 8, 2022 .

• Research team led by Isabella Eckerle and Benjamin Meyer from the University of Geneva were involved in the study.

• Between April 2020 and February 565 people with a corona infection had nasal mucosa swabs taken five days after the onset of symptoms.

• Some of the samplers were not vaccinated, others were vaccinated twice or boosted.

Corona: Ct value and infectious virus particles

The scientists then determined the so-called Ct value, which indicates how much genetic material of the virus is present in a sample.

In addition, they determined the amount of infectious virus particles in a sample using cell culture experiments.

This is a better indicator of a sick person's contagiousness, as the researchers' studies confirmed.

The evaluation of the data showed that people who had been vaccinated twice had significantly fewer infectious particles in the upper respiratory tract than those who had not been vaccinated, namely almost a fifth.

According to the study, vaccinated people were also able to fight the virus faster.

In omicron breakthrough infections, the amount of infectious virus particles was as high after double vaccination as in unvaccinated subjects.

Only a booster vaccination pushed the value down to about a fifth.

Corona: During omicron wave, researchers found overall lower amounts of infectious particles in the vaccinated subjects than during delta wave

Another result: During the omicron wave, the researchers found significantly lower amounts of infectious particles in the vaccinated subjects than during the delta wave - despite the higher contagiousness of the omicron variant.

They conclude that omicron-infected people are not more contagious because they excrete more viruses.

The entry mechanism of the virus into the cell may be different.

The researchers point out that it is not known from what amount of detected virus particles an infected person is contagious.

The fluctuations in the amount of virus could also have been influenced by the respective quality of the smear or by the fact that the samples were not taken from all subjects at the same time of infection.