During the pandemic, it became increasingly clear that it is older people who are hardest hit by covid-19. Young children, on the other hand, rarely become seriously ill. The reason for this has been unclear, although theories have existed that colds can have a protective effect.
Now researchers at Karolinska Institutet have shown that one of the common cold viruses, OC43, which often affects young children, probably trains their immune system even against Sars Cov 2.
"We have seen that children between the ages of 2 and 6, who have had this cold virus, also have protection against Sars Cov 2, even though they have not previously been exposed to it," says immunologist Annika Karlsson.
Blood tests showed different results
The researchers have analyzed 48 blood samples taken from children before the pandemic. In these, they found T cells that reacted even against Sars Cov 2. Blood samples from older adults did not show nearly the same results.
"We believe that a previous infection with a cold virus helps the T-cells to trigger the immune system's reaction even against Sars Cov 2 in young children. In older adults, there was not nearly the same effect. This may explain why children do not get as sick in corona as older people," says Annika Karlsson.
The study, published in the journal PNAS, could lead to more tailored vaccine programs for children and adults.