Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Polio Vaccination Strategies Assessed as Eradication Nears

21.12.2005


Polio is on track to become only the second disease ever eradicated. In two studies in the Dec. 15 issue of The Journal of Infectious Diseases, now available online, scientists are working to ensure that once it is gone, it stays gone. One study reduces concerns that people whose immune systems were weakened by HIV would re-introduce poliovirus into the community. The other study looks at the how switching forms of vaccine from a live, attenuated vaccine to an inactivated version may affect communities.



Oral polio vaccine (OPV), one of the vaccines instrumental in driving the disease to near-eradication, contains weakened live virus strains. The vaccine is highly effective, easy to administer, relatively inexpensive, and has been used for more than 40 years. Those given the vaccine excrete, or “shed,” virus in their stool. There is some concern over the use of OPV, however, because vaccine-derived poliovirus (VDPV) can occasionally cause another form of polio.

Furthermore, in rare cases, immunodeficient persons have shown prolonged shedding of VDPV, which may be transmitted to contacts, thus potentially re-introducing polio into the community. Concerns had been raised that this issue would be a particular challenge in countries with high HIV prevalence.


Karen Hennessey, PhD, MSPH, and colleagues in Cote d’Ivoire and at the Centers for Disease Control and Prevention examined the duration of shedding of oral poliomyelitis vaccine by individuals with HIV infection.

Dr. Hennessey and colleagues tested stool specimens at various intervals following vaccination. Out of a total of 419 adults with HIV infection, no poliovirus was isolated from any of the specimens. Because of these results, it is likely that fewer than 1 percent of adults with HIV infection experience prolonged virus shedding when exposed to OPV, “and therefore probably represent minimal risk of re-introducing vaccine virus into the population after poliovirus has been eradicated,” the authors concluded.

The alternative to OPV, a live virus vaccine, is an inactivated polio vaccine (IPV). IPV is safer because the inactivated virus in IPV cannot mutate into paralytic VDPV. However, the immune response generated in the digestive tract by IPV was believed to be less potent that that of OPV. Therefore, although those immunized with IPV would be protected from polio, they could still be infected and shed virus, contributing to the spread of the disease.

But all research on the subject had been performed using only one dose of a vaccine that was less potent that the currently used version. Konstantin Chumakov, PhD, and colleagues at the Food and Drug Administration and various other institutions throughout the United States revisited the issue using two doses of the newer, enhanced vaccine.

They found that two doses of IPV did produce immunity in the digestive tract. The researchers used shedding of virus after treatment with a dose of OPV to measure the immune response. Seventy-five percent of children receiving two doses of IPV, followed by one dose of OPV, shed OPV virus a week later, compared to 92 percent of those receiving just one dose of OPV. After three weeks, 81 percent of the children receiving one OPV dose were still shedding virus, while only 37 percent of those immunized with IPV first were. The amount of virus shed was also lower in those receiving IPV.

However, the mucosal immunity generated by IPV was less than that achieved by OPV. After two doses of OPV, only 22 percent of children given a third dose of OPV were shedding virus after a week. That figure dropped to 5 percent after three weeks.

The researchers concluded that IPV-immunized communities are partially protected from spread of poliovirus. Better protection may be achieved by enhancing IPV further, they said.

However, an accompanying editorial by Harry F. Hull, MD, and Philip D. Minor, MD, at the Minnesota Department of Health and the U.K. National Institute for Biological Standards and Control noted that “the time and expense of developing, testing and securing regulatory approval for a new IPV makes it unlikely that such a vaccine could be available on a timely basis.” They also discussed public health, ethical, and financial reasons for stopping vaccination once poliovirus is effectively non-existent, and the risks associated with doing so. Whereas Hull and Minor blame politics and complacency as ultimately being the biggest threats to polio eradication, they conclude that choosing an appropriate vaccination strategy to prevent poliovirus re-introduction is an important and unavoidable task.

Steve Baragona | EurekAlert!
Further information:
http://www.idsociety.org

More articles from Health and Medicine:

nachricht Study tracks inner workings of the brain with new biosensor
16.08.2018 | Rheinische Friedrich-Wilhelms-Universität Bonn

nachricht Foods of the future
15.08.2018 | Georg-August-Universität Göttingen

All articles from Health and Medicine >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Unraveling the nature of 'whistlers' from space in the lab

A new study sheds light on how ultralow frequency radio waves and plasmas interact

Scientists at the University of California, Los Angeles present new research on a curious cosmic phenomenon known as "whistlers" -- very low frequency packets...

Im Focus: New interactive machine learning tool makes car designs more aerodynamic

Scientists develop first tool to use machine learning methods to compute flow around interactively designable 3D objects. Tool will be presented at this year’s prestigious SIGGRAPH conference.

When engineers or designers want to test the aerodynamic properties of the newly designed shape of a car, airplane, or other object, they would normally model...

Im Focus: Robots as 'pump attendants': TU Graz develops robot-controlled rapid charging system for e-vehicles

Researchers from TU Graz and their industry partners have unveiled a world first: the prototype of a robot-controlled, high-speed combined charging system (CCS) for electric vehicles that enables series charging of cars in various parking positions.

Global demand for electric vehicles is forecast to rise sharply: by 2025, the number of new vehicle registrations is expected to reach 25 million per year....

Im Focus: The “TRiC” to folding actin

Proteins must be folded correctly to fulfill their molecular functions in cells. Molecular assistants called chaperones help proteins exploit their inbuilt folding potential and reach the correct three-dimensional structure. Researchers at the Max Planck Institute of Biochemistry (MPIB) have demonstrated that actin, the most abundant protein in higher developed cells, does not have the inbuilt potential to fold and instead requires special assistance to fold into its active state. The chaperone TRiC uses a previously undescribed mechanism to perform actin folding. The study was recently published in the journal Cell.

Actin is the most abundant protein in highly developed cells and has diverse functions in processes like cell stabilization, cell division and muscle...

Im Focus: Lining up surprising behaviors of superconductor with one of the world's strongest magnets

Scientists have discovered that the electrical resistance of a copper-oxide compound depends on the magnetic field in a very unusual way -- a finding that could help direct the search for materials that can perfectly conduct electricity at room temperatur

What happens when really powerful magnets--capable of producing magnetic fields nearly two million times stronger than Earth's--are applied to materials that...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Within reach of the Universe

08.08.2018 | Event News

A journey through the history of microscopy – new exhibition opens at the MDC

27.07.2018 | Event News

2018 Work Research Conference

25.07.2018 | Event News

 
Latest News

Interactive software tool makes complex mold design simple

16.08.2018 | Information Technology

Study tracks inner workings of the brain with new biosensor

16.08.2018 | Health and Medicine

Fraunhofer HHI develops next-generation quantum communications technology in the UNIQORN project

16.08.2018 | Information Technology

VideoLinks
Science & Research
Overview of more VideoLinks >>>