Dec. 30, 2021

The following is a summary of some recent studies on COVID-19. They include research that warrants further study to corroborate the results and that has not yet been certified by peer review.

Omicron can’t escape the body’s second line defense

A key part of the immune system’s second-line defense – its T cells – is very effective at recognizing and attacking the Omicron variant, preventing most infections from progressing to serious disease, according to a new study.

Omicron’s mutations help it escape antibodies, the body’s first line of defense against infection. The researchers speculated that other components of the immune response would still target Omicron, but there has been no evidence so far.

In test-tube experiments, researchers in South Africa exposed copies of the virus to T cells from volunteers who had received vaccines from Johnson & Johnson or Pfizer / BioNTech or who had not been vaccinated but had developed their own T cells after infection with an earlier version. of the coronavirus.

“Despite Omicron’s widespread mutations and reduced susceptibility to neutralizing antibodies, the majority of the T-cell response, induced by vaccination or natural infection, recognizes the variant,” the researchers reported Tuesday on medRxiv ahead of the review. by peers.

“Well-preserved T cell immunity against Omicron is likely to help protect against severe COVID-19,” confirming what South African doctors initially suspected when most patients infected with Omicron did not have serious illnesses. sick, they said.

The “T” stands for thymus, the organ in which the final stage of cell development occurs.

Boosters reduce risk of home transmission Omicron

The chances of vaccinated people catching the virus if a household member is infected are nearly three to four times higher with Omicron than with Delta, but booster doses reduce that risk, new findings suggest.

The researchers analyzed transmission data collected from nearly 12,000 infected homes in Denmark, including 2,225 homes infected with Omicron. Overall, there were 6,397 secondary infections within a week of the first infection in the home. After taking other risk factors into account, the rate of person-to-person spread of the virus to fully vaccinated people was about 2.6 times higher in Omicron households than in Delta households, the researchers reported Monday on medRxiv before peer review.

People vaccinated by a booster were nearly 3.7 times more likely to be infected in Omicron households than in Delta households, they found.

Looking only at Omicron households, however, those who received the booster were 56% less likely to be infected compared to those vaccinated who had not received the booster. And overall, when booster-vaccinated people were the first to bring home the virus, they were less likely than unvaccinated and vaccinated but unboosted people to pass it on to others.

REUTERS