Influenza-specific bone marrow plasma cells - responsible for maintaining the level of protective antibodies following a flu shot - are short-lived, and decline to their pre-vaccination levels within a year, researchers report.

While the findings help explain the lackluster persistence of the antibody response often observed from the annual influenza vaccination, the new study offers insight into how the longevity of the next generation of vaccines could be enhanced.

 Ideally, a successful vaccine stimulates the body's adaptive immunity to produce pathogen-specific antibodies, which imbues an individual with long-lasting protection against future infection.
For many vaccines, the levels of a new antibody peak in the months following vaccination and decline to a "plateau level" that can be maintained for decades. However, this is not the case for common influenza vaccines; antibody levels and protective immunity decline rapidly after each seasonal vaccination.

In a novel clinical study that spanned eight flu seasons and 53 participants, the authors tracked the production and maintenance of influenza-specific bone marrow plasma cells (BMPCs) following flu vaccination. They collected bone marrow samples pre-vaccination, one month post-vaccination and one year post-vaccination, which allowed the authors to assess the long-term vaccine response and antibody maintenance. For some individuals, they assessed this for several seasonal vaccination cycles.

The results showed that vaccination did spur the generation of influenza-specific BMPC, which were present in increased numbers a month following immunization. However, most of the newly formed BMPC were quickly lost, returning to pre-vaccination levels within a year.

Despite this, the authors show that a small number did persist more than a year, suggesting that the longevity of flu vaccines can be improved.

https://science.sciencemag.org/content/early/2020/08/12/science.aaz8432

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