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  4. Variant Creutzfeldt-Jakob Disease (vCJD) and Factor XI (pdFXI) Questions and Answers
  1. Safety & Availability (Biologics)

Variant Creutzfeldt-Jakob Disease (vCJD) and Factor XI (pdFXI) Questions and Answers

What is vCJD and how is it spread?

Variant Creutzfeldt-Jakob disease, or vCJD, is a very rare, fatal disease that can infect a person for many years before making them sick by destroying brain cells. Eating beef and beef products contaminated with the infectious agent of bovine spongiform encephalopathy (BSE) is the main cause of vCJD.

Most cases of vCJD have occurred in the United Kingdom (UK). Individuals in the UK are at a greater risk for this rare disease than are individuals elsewhere because of the previous higher risk of potential exposure to contaminated beef in the UK diet. From 1995 through April 2007 there have been 202 individuals with vCJD reported worldwide, 165 of them in the UK. In the United States (US), there have been three reported cases of vCJD. Two of these individuals had lived in the UK during 1980-1996, a key exposure period to the BSE agent. The third US individual with vCJD probably acquired the infection in Saudi Arabia.

The reported incidence of vCJD in the UK, based on disease onset, peaked in 1999 and declined thereafter. In the UK, where most cases of vCJD have occurred, the current risk of acquiring vCJD from eating beef and beef products appears to be negligible.

Only three cases of BSE have been found in US cattle, and safeguards are in place to help prevent infected beef products from entering our food supply. These safeguards include restricting importation of cattle and beef products from almost all countries with BSE, a surveillance program to detect BSE in the US, prohibiting the use of high-risk animal-derived proteins in cattle feed, prohibiting meat from sick cattle to be used for human consumption, and requiring the removal of high-risk materials from carcasses of cattle over a certain age.

While vCJD is primarily due to eating infected beef and beef products, four people in the UK became infected with the vCJD agent after receiving red blood cells from three donors who later developed vCJD. Three of the red blood cell recipients developed typical vCJD and died from the disease. A fourth died of an unrelated illness but had evidence of infection. To date, there have been no reports of vCJD transmission by close personal contact (such as being in the same room with someone who has vCJD, hugging, kissing, or having sexual relations).

How does vCJD differ from Creutzfeldt-Jakob disease (CJD)?

A. Both vCJD and CJD cause progressive degeneration of the brain leading to death. However, the variant form-never seen before 1994-usually affects persons much younger than other forms of CJD. Unlike CJD, vCJD has been acquired by food exposure and transmitted by blood transfusion. vCJD also has somewhat different clinical symptoms, a longer survival after onset of illness (the majority of illnesses lasting more than one year), and produces a characteristic abnormality in brain tissue called "florid plaques" rarely if ever seen in the other forms.

Is it known that pdFXI can transmit vCJD?

No. However, pdFXI is made from plasma. Plasma is the liquid part of blood remaining after the cells are removed. Animal studies show that if blood carries the vCJD agent, so can the unprocessed plasma.

Manufacturing steps used in making pdFXI have been shown to help remove infectious agents, including agents similar to that causing vCJD. The manufacturing steps may reduce or eliminate most risk even if a vCJD-infected donor contributed plasma.

What is the likelihood that a patient who received pdFXI could have become infected with vCJD?

The US PHS believes the risk of developing vCJD infection from pdFXI is likely to be small. Many unknowns prevent us from accurately determining the risk using a computer model, and we believe the risk is likely to be smaller than the modeling predicts. However, we do not know this with certainty. Right now, there is no test available to detect vCJD in blood donors or recipients. There is no way of knowing whether a person is infected if they do not show symptoms of the disease.

At this time FDA, CDC, and NIH are not aware of any cases of vCJD having been reported worldwide in patients receiving plasma-derived clotting factors, including pdFXI. This includes patients who have received, over a long period of time, large amounts of clotting factor products manufactured from plasma donations from the UK, where the risk of vCJD is highest.

Why did FDA do a vCJD risk assessment for pdFXI made from UK plasma?

We conducted a risk assessment on pdFXI because it was made from plasma obtained from donors in the UK. The UK population, including UK plasma donors, is at a considerably higher risk for vCJD than the US population due to eating food potentially contaminated with the BSE agent, although the estimates of risk vary widely. We believe that pdFXI is the only plasma product used in the US that was manufactured from UK donor plasma collected during the BSE epidemic. Note, however, that plasma pools used to manufacture the pdFXI product infused in the US did not contain donations from individuals known to have developed vCJD (that is, there were no known "implicated" lots).

Why is FDA informing patients, healthcare providers, and the public about vCJD and pdFXI now?

A. The FDA has recently completed its risk assessment, and we think it is important that a person who received pdFXI be aware of the results of the risk assessment and have an opportunity to discuss any questions with a suitable health care provider.

The first case of probable vCJD infection transmitted by transfusion of red blood cells in the UK was reported in December 2003 and the second case in July 2004. These events prompted UK authorities in 2004, to communicate the potential risk of vCJD to recipients of clotting factors and some other plasma derived products. FDA initiated its risk assessment for pdFXI in 2004, and presented a draft to the Transmissible Spongiform Encephalopathies Advisory Committee (TSEAC) in February 2005 (draft risk assessment, meeting transcript and slides). Since then FDA, with scientific advice from the TSEAC in October 2005, and other experts, has further refined the risk assessment and risk communication materials. Results of this extensive analysis are now available.

FDA, CDC, NIH, and the Office of Public Health and Science (OPHS) of the US Department of Health and Human Services, with advice from patient advocacy groups and communication experts, have now developed key message points and communication materials to accurately convey the possible risk to patients, health care providers, and others who may have an interest.

Should patients inform their primary health care providers about a possible vCJD exposure from UK pdFXI?

Advising your primary health care provider (e.g., a family physician, internist, blood disease specialist, etc.) about your history of having received the pdFXI product might be beneficial in that your provider can keep you informed about new information as it becomes available, interpret its significance, and advise you about further appropriate actions in the future. However, sharing your personal health information is your choice.

Do patients who received UK pdFXI need to do anything special when seeking dental or surgical care?

At this time, the US PHS does not believe that UK pdFXI recipients need to inform their surgeons or dentists about the potential exposure to vCJD. Also, the US PHS does not recommend that surgeons and dentists take any special precautions with patients who had such potential exposures. This belief is based on the very large degree of uncertainty in the FDA risk assessment, and the lack of known cases of vCJD transmitted by plasma-derived clotting factor products in the UK, where risk is considered greatest, or anywhere else in the world. Also, there were relatively few patients exposed to the pdFXI product in the US compared to the large number of recipients of plasma-derived clotting factors, of which pdFXI is only one of many, in the UK.

In the UK, public health authorities notified recipients of plasma-derived products, such as pdFXI, that they may have an increased risk of vCJD in addition to their risk from eating potentially contaminated UK beef products. The UK health authorities asked patients to inform their surgeons and dentists about their potential exposure as a public health precaution intended to prevent possible secondary spread of the disease from dental and surgical instruments. The US PHS, including the FDA, CDC, and NIH, does not believe that such notifications are necessary in the US. This belief is based on the very large degree of uncertainty in the FDA risk assessment, and on the lack of known cases of vCJD transmitted by plasma-derived clotting factor products in the UK or anywhere else in the world. Given this information, the PHS believes that there is no need to alter the standard current practices.

PHS agencies will continue to monitor and reevaluate the situation as new information becomes available.

What can recipients of pdFXI do with this information?

While no new actions are recommended now, you can stay informed by keeping in contact with your primary physician and/or a specialist in bleeding disorders, such as a hemophilia specialist at a Hemophilia Treatment Center. Such contact will help you to learn about any new scientific advances in this field such as testing and diagnosis, and also to monitor your general health.

What are Hemophilia Treatment Centers, and where can I find out about them?

Hemophilia Treatment Centers (HTC) are a network of federally funded comprehensive care clinics that promote the management, treatment, and prevention of complications experienced by persons with hemophilia and other hereditary bleeding disorders.

You can find information about HTC's at:

  1. CDC informational posting, containing information about the kinds of services provided by federally funded HTC's
  2. Regional HTC websites are also a good place for information

Where can I find more information about vCJD and pdFXI?

A. You can find additional information at:


  • FDA informational posting, containing current pdFVIII risk assessment, fact sheet, and briefing materials
  • Blood Products Advisory Committee meeting - summary of recent TSEAC meeting and statement about pdFXI from the UK, on October 21, 2006
  • TSEAC meeting with discussion of first pdFXI draft risk assessment, on February 8, 2005, and discussion of UK risk communication for plasma derivatives
  • TSEAC Meeting with further discussion of the FDA risk assessment model, October 31, 2005
  • TSEAC Meeting with update on pdFXI risk assessment, September 18, 2006

CDC: vCJD (Variant Creutzfeldt-Jakob Disease)

Regional HTC websites

US Department of Agriculture: Bovine Spongiform Encephalopathy

Patient Organizations:

Committee of Ten Thousand
Hemophilia Federation of America
National Hemophilia Foundation and/or HANDI
World Federation of Hemophilia

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