Yellow fever vaccination: The reason for its long-lasting effectiveness

The yellow fever vaccination with the live vaccine YF17D is one of the most effective Vaccinations at all. Even a single dose provides long-lasting protection. The German Standing Committee on Vaccination (STIKO) recommends a single booster vaccination before renewed or continued exposure, provided that ten or more years have passed since the initial vaccination. After the second dose of vaccine, no further booster vaccinations are necessary. Exceptions and special rules apply only to certain groups of people, such as pregnant women, people with immunodeficiency, and children .

It is still largely unclear why this vaccine triggers such a strong immune response. A team led by Dr. Elena Winheim from the Ludwig-Maximilians-University of Munich (LMU Munich) recently published the results of a study in the journal "PNAS" that could provide an answer to this previously unsolved mystery. The scientists tested how dendritic cells (DCs) and monocytes respond to the vaccination. For this purpose, various DC and monocyte cell types from the blood of more than 200 healthy adults were analyzed before and after vaccination. After vaccination, many of these immune cells showed typical activation by interferons, which play a major role in virus defense.

Particularly striking was the cell surface molecule SIGLEC-1, which increased in certain cell types within a week of vaccination and was associated with the rapid formation of protective antibodies against the yellow fever virus. "Our study provides new insights into exactly how the immune system responds to a highly effective vaccination," says senior author Professor Dr. Anne Krug, also of LMU Munich, in a university press release. This could help develop new vaccines that provide rapid protection, for example, in emerging epidemics. Furthermore, according to the expert, SIGLEC-1 could serve as a useful biomarker in vaccination studies in the future.