Immune memory from vaccination lasts more than 50 years.

2003 DEC 3 - (NewsRx.com & NewsRx.net) -- Immune memory after smallpox vaccination persists for at least 50 years in immunized people, according to research conducted by scientists at the Emory Vaccine Center and Emory University School of Medicine.

This is good news, since the findings, published in the Journal of Immunology, suggest that individuals vaccinated against smallpox prior to the end of the smallpox vaccination program in 1972 may still retain at least some protection against smallpox.

Rafi Ahmed, PhD, Georgia Research Alliance Eminent Scholar and director of the Emory Vaccine Center, was principal investigator of the research study, and Shane Crotty, PhD, formerly at Emory University School of Medicine and currently a faculty member at the La Jolla Institute for Allergy and Immunology, was first author. Other members of the research team included Emory microbiologist John Glidewell, Phil Felgner, and Luis Villarreal of the University of California, Irvine, and Huw Davies of King's College London.

Although scientists have known that acute viral infections and vaccines produce two types of long-term immune memory that provide protection against disease, they are still learning the details of these immune mechanisms.

Using a new blood test they developed to assess human antigen-specific immunity, the Emory scientists measured memory B cell responses in individuals recently vaccinated with smallpox vaccine (DryVax), in unvaccinated individuals, and in individuals vaccinated between 3 months and 60 years earlier. The recently vaccinated group showed a significant virus-specific memory B cell response to vaccinia, while the unvaccinated individuals were negative for vaccinia virus-specific memory B cells. Vaccinia virus-specific B cells were detected in most of the previously vaccinated individuals in the study, including those vaccinated up to 60 years after vaccination.

The scientists found that virus-specific memory B cells initially declined after smallpox immunization, but then reached a plateau approximately 10 times lower than their peak, where they remained stable for more than 50 years. Although there were significantly fewer memory B cells in the most recently vaccinated group compared to those vaccinated decades earlier, there was no significant change in B cell memory between 20 and 60 years after vaccination. In addition, individuals vaccinated against smallpox maintained antismallpox antibodies in their blood for at least 60 years after vaccination, with no indication of decline between 1 and 60 years.

In humoral immunity, the body's first line of defense against infection is antibodies produced by B cells, which are the primary measure of immunity for most vaccines. Memory B cells are responsible for stimulating a rapid ...