“Along with viral factors, such as a lower level of viral replication in the lower airways, and other immune components, these results give us a clearer picture that may explain why the protection against severe omicron disease remains good in previously mRNA-vaccinated individuals,” says principal investigator Marcus Buggert at Karolinska Institutet’s Center for Infectious Medicine.
The study is a collaboration with the Karolinska University Hospital in Sweden and is based on blood samples from 40 vaccinated individuals, 48 individuals who had had a mild or severe SARS-CoV-2 infection, and 48 individuals who had previously been neither vaccinated nor infected.
The samples from the vaccinated group were collected six months after their second vaccine dose, and from the previously infected group 9 months after confirmed infection in the spring of 2020, before the emergence of the new viral variants. Other samples were taken from healthy donors at the end of 2020.
Memory T cells in both the experimental groups displayed a good ability to recognize the omicron spike protein; the best response, however, was observed in the vaccinated group.
These results suggest that booster immunization may provide benefits that extend beyond the induction of neutralizing antibodies to enhance protection against recurrent episodes of severe COVID-19.
Even though the memory T-cell response was generally intact against omicron, some individuals did not respond as well.
Researchers want to understand why the response differs from one individual to the next and if a third vaccine dose can augment the T cell response to omicron even more in the future.
Source: Medindia
