OHSU researchers study vaccination protection over time.

2003 MAR 5 - (NewsRx.com & NewsRx.net) -- Oregon Health & Science University (OHSU) researchers are studying the effectiveness of the smallpox vaccine in patients who received inoculations decades ago compared with those vaccinated more recently.

The universal belief has been that smallpox vaccinations provide protection for only 4-5 years. Until now scientists and physicians assumed that anyone vaccinated more than 5 years ago had little to no protection left. However, researchers at the OHSU Vaccine and Gene Therapy Institute believe that conventional thinking may not be true.

To test their theories, scientists are studying how much protection the smallpox vaccination provides 67 years later versus just a year ago. This information may provide a more accurate way of estimating the spread of a potential smallpox outbreak, because nearly 95% of Americans older than 35 were vaccinated, and many may still have strong immunity against smallpox.

"I've been intrigued about immunological memory for more than a decade. It's exciting to be able to apply this interest to something that's relevant to our community right now," said Mark Slifka, PhD, assistant professor of molecular microbiology and immunology in the OHSU School of Medicine. "We know that people who contract yellow fever, polio, measles or mumps gain a lifelong immunity to those diseases. Now we want to see if this is universally true for other viruses, such as vaccinia, the virus used for immunizing against smallpox."

Vaccinia is a virus contained within the smallpox vaccine and is closely related to smallpox. However, in most cases, vaccinia does not cause serious health problems. The virus promotes smallpox protection by causing the body to produce protective antibodies and white blood cells that can search for and destroy smallpox-infected cells.

Slifka's lab is collecting blood samples from study participants. These samples are then analyzed to determine the participants' level of immunity against smallpox. Of the participants that have joined this ongoing study, 6 people were vaccinated within the last 7 years while more than 100 were vaccinated between 15 and 67 years ago. His team is comparing the immunity of both groups to determine whether the vaccine truly loses potency over time.

This study looks at the effectiveness of both arms of the body's adaptive immune response: antibodies and T-cells. Blood samples from study participants are exposed to vaccina in petri dishes, the same virus used in the smallpox vaccine. If a person has strong immunity against vaccina, then his/her antibodies will neutralize the virus, thus saving healthy cells from becoming infected. If the virus is able to slip past this first line of defense and actually cause an infection, ...