T cells prevent the disease from developing seriously after the first vaccination. However, only after the second vaccination dose do antibodies offer reliable protection against infection.
In view of the continuing high number of infections worldwide, vaccination offers important protection against a serious illness from COVID-19. Scientists from the CRC 1160 (Medical Faculty of the University of Freiburg) have now been able to break down in detail when, after vaccination with an mRNA-based vaccine, initial immune protection can be determined and how the reactions of the various components of the human immune system develop over months. The researchers published their results on July 28, 2021 in the online edition of the renowned journal Nature.
“Just ten days after the first vaccination dose, there is effective protection against a serious course of the disease. At this point, however, neutralizing antibodies that prevent the virus from entering the cells are hardly detectable. Instead, this early protective effect is due to specific T cells that control the cellular immune response, ”says Dr. Maike Hofmann (A02), head of a research group in the Clinic for Internal Medicine II at the Medical Center – University of Freiburg.
Detailed analysis of the immune response
The scientists examined blood samples from 32 subjects before the first COVID-19 vaccination dose and continuously for up to four months after the second vaccination dose at intervals of three to four days. This enabled them to follow the development of the various components of the immune response in detail. “In the majority of our test subjects, a relevant increase in so-called CD8+ T cells, which are precisely tailored to the SARS-CoV-2-typical spike protein, was detected just six to eight days after the initial vaccination,” reports Prof. Dr. Christoph Neumann-Haefelin (A06), Head of the Gerok Liver Center at the Medical Center – University of Freiburg.
After the second dose of vaccine, the number of CD8 + T cells increased. It was only at this point in time that neutralizing antibodies could be detected in such large quantities that they could prevent the virus from penetrating and thus the infection itself. “Our results therefore also underline the importance of a complete vaccination with two doses of the mRNA vaccine for good protection against infection,” adds Neumann-Haefelin.
High effectiveness of mRNA vaccination technology
The effective combination of a fast T cell response and neutralizing antibodies is evidence of the high effectiveness of the still new mRNA vaccination technology. Follow-up studies should show how long the protection lasts after the second vaccination dose and when a booster vaccination – possibly adapted to new virus variants – is required. “The more precisely we understand the mode of action of the mRNA vaccination, the sooner we can develop it further for other diseases – for example for a future vaccination against hepatitis C or a therapeutic vaccination for tumor diseases,” explains Prof. Dr. Robert Thimme (A02), Medical Director of the Clinic for Internal Medicine II at the Medical Center – University of Freiburg.
Original-title of the study: Rapid and stable mobilization of CD8+ T cells by SARS-CoV-2 mRNA vaccine