The authors analyzed not only the amount of antibodies, but also the amount of B cells (they trigger antibody production) and two types of T cells that remember the first infection and then attack infected cells in the second. They wanted to get as complete a picture of the immune system’s reaction as possible – not just the antibody reaction.
The antibody level decreased only slightly over an average of six to eight months, but the difference between the study participant with the lowest amount of antibody and the one with the highest was 200-fold. The number of T cells only slowly decreased, while the number of B cells actually increased – a very unexpected study result.
However, a small proportion of the study participants did not have long-lasting immunity after recovery – possibly because they were infected with only a small amount of the virus.
In the past few months, several papers have been published that indicated a rapid decline in antibodies and showed the possibility of a new infection within a year. But recently there has been increasing data that this is apparently not the rule and also does not mean that there is no longer any protection:
Because a certain decrease in antibodies is quite natural and the immune system also has several defense strategies, in addition to the antibodies, the various forms of defense cells. For example, researchers at the University of Washington have shown that certain memory cells of the immune system are produced for at least three months after an infection. Other research groups also assume longer-term protection.