Questions and Answers on Bovine Spongiform Encephalopathy
Questions and Answers on Bovine Spongiform Encephalopathy:
What is BSE?
What causes BSE?
Where is the BSE agent found in infected cattle?
Which countries have reported BSE?
How was BSE spread?
What has the British government done in response to the BSE epidemic?
Does BSE occur in the US?
What measures has the US government taken to ensure that BSE does not occur in the US, and that people are not exposed to the BSE agent in foods?
How is the BSE agent detected?
Does BSE or a similar disease occur in humans?
Questions and Answers on Variant CJD (vCJD):
What is the new variant form of CJD that the experts in the United Kingdom believe might be related to the BSE outbreak in cattle?
Exactly how does this newly recognized variant of CJD differ from classical CJD?
How did people get this new variant of CJD?
What is the evidence directly linking this newly recognized variant of CJD to BSE exposure?
How many cases of variant CJD have occurred?
Could anyone in Europe diagnosed with the newly recognized variant of CJD (vCJD) have acquired this from vaccines?
Questions and Answers on Bovine Derived Materials Used in Vaccine Manufacturing:
Why are animal products used in the manufacture of vaccines?
Which bovine derived materials are used in vaccine manufacture?
Do all bovine materials have the same risk of transmitting the BSE agent?
What measures have the FDA taken to ensure that people are not exposed to the BSE agent in vaccines?
Questions and Answers Related to FDA Guidance on Sourcing of Bovine Materials:
How did the FDA discover that some manufacturers are not universally following letters, PTC and guidance documents?
What is FDA doing now to assure that companies follow guidance, letters, and PTC documents?
Questions and Answers Related to Vaccines and vCJD:
Why did the FDA ask the Transmissible Spongiform Encephalopathy Advisory Committee and the Vaccines and Related Biological Products Advisory Committee meet on July 27th, 2000?
What is the chance/risk that a vaccine on the market in the US contains the BSE agent?
What is the risk of getting vCJD if a vaccine contained the BSE agent?
How did FDA derive its risk estimates and decide the risk of vCJD from vaccines was remote and theoretical?
Why is FDA leaving vaccines on the market that did not follow its own recommendations regarding sourcing of bovine derived materials?
If vaccines are safe, why did the UK recall the polio vaccine?
What is the recent concern in the Republic of Ireland about polio vaccine and vCJD?
Have there been vaccines produced using cow materials from countries where there is a significant risk of BSE?
Is there a possibility that some vaccines might be contaminated with the BSE agent?
My child was just immunized. Should I be worried?
Why are you continuing to vaccinate children with a vaccine that may be contaminated with BSE causing materials?
What is being done to ensure the United States?vaccine supply is safe?
When will vaccine manufacturers finish replacing cow-derived materials in vaccines with materials obtained from countries free of BSE?
Shouldn抰 all potentially contaminated vaccines be destroyed?
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What is BSE?
BSE (bovine spongiform encephalopathy) is a progressive neurological disorder of cattle; its symptoms are similar to a disease of sheep, called scrapie. BSE has been called "mad cow disease." BSE and scrapie both result from infection with a very unusual infectious agent. As of July 2000, more than 176,000 cases of BSE were confirmed in Great Britain in more than 34,000 herds of cattle. The epidemic peaked in January 1993 at almost 1,000 new cases per week. The outbreak may have resulted from the feeding of scrapie-containing sheep meat-and-bone meal to cattle. There is strong evidence and general agreement that the outbreak was amplified by feeding meat-and-bone meal prepared from cattle to young calves.
What causes BSE?
The nature of the infectious agent that causes BSE and scrapie is unknown. Currently, the most accepted theory is that the agent is a modified form of a normal cell protein known as a prion. A prion is not a bacterium, parasite, or virus, and thus treatments usually used for treating or preventing bacterial infections (e.g. antibiotics) or viral infections are not effective against prions.
Where is the BSE agent found in cattle?
In cattle naturally infected with BSE, the BSE agent has been found in brain tissue, in the spinal cord, and in the retina of the eye. Additional experimental studies suggest that the BSE agent may also be present in the small intestine, bone marrow, and dorsal root ganglia.
Which countries have reported BSE?
The vast majority of cases of BSE (more than 99% as of 1999) have been reported from the United Kingdom during an epidemic. However, endemic cases have also been reported in other European countries including: the Republic of Ireland, Switzerland, France, Liechtenstein, Luxembourg, Netherlands, Portugal and Denmark. The numbers of reported cases by country are available on the web site of the Office International des Epizooties (www.oie.int/). These numbers should be interpreted with caution, however, because the intensity and methods of surveillance probably vary over time and by country.
How was BSE spread?
It is thought that BSE was spread via meat-and-bone meal fed to cattle. The practice of using this material as a source of protein in cattle feed has been common for several decades. In the late 1970s there was a change in the production (rendering) process used to make this meat and bone meal. One hypothesis is that this change permitted the infectious agent of scrapie (a transmissible spongiform encephalopathy, or TSE, of sheep) to survive the rendering process, and get transmitted to other animals, such as cows, that are fed meat-and-bone meal nutritional supplements.
What has the British government done in response to the BSE epidemic?
In response to the BSE epidemic, the British Government instituted a series of measures to minimize the risk of disease transmission among both animals and humans. These included a ban on feeding ruminant protein (ruminants are animals, such as cows, sheep and goats) to ruminants (1988), removal of some "high risk" materials (such as brain, spinal cord and intestines) from cattle at slaughter (1989 and 1995), and a ban on cattle over 30 months of age from being used for food (1996). Following institution of these measures, Great Britain has seen a decrease in the number of cattle with BSE from a peak incidence of 36,680 confirmed cases in 1992 to 2,254 confirmed in 1999 (information on the BSE epidemic in Great Britain is available at: http://www.maff.gov.uk/).
Does BSE occur in the US?
According to the Animal and Plant Health Inspection Services (APHIS) of the United States Department of Agriculture, BSE has not been detected in the United States, despite active surveillance efforts for several years. As of May 31, 2000, 10,670 cow brains have been examined by US inspectors, and no evidence of BSE was seen. Further, to prevent BSE from entering the United States, severe restrictions have been placed on the importation of live ruminants and certain ruminant products from countries where BSE was known to exist. Recently, these restrictions were extended to include importation of ruminants and certain ruminant products from all European countries.
What measures has the US government taken to ensure that BSE does not occur in the US, and that people are not exposed to the BSE agent in foods?
The USDA is responsible for the health of US livestock. To prevent BSE from entering the country, the USDA Animal and Plant Health Inspection Service (APHIS) has, since 1989, prohibited the importation of live ruminants from countries where BSE is known to exist in native cattle. On December 12, 1997, APHIS stopped the importation of live ruminants and most ruminant products, including meat, meat-and-bone meal, offals, glands, etc. from all of Europe. FDA is responsible for food safety in the US. In August 1997, FDA prohibited the use of most mammalian protein in the manufacture of animal feeds given to ruminants. In addition, the final regulation also requires quality control procedures to make sure that ruminant feed does not contain the prohibited mammalian tissues. The USDA leads an interagency surveillance program for evidence of BSE in the US. No cases of BSE have been confirmed in the US despite 10 years of active surveillance.
How is the BSE agent detected?
The presence of the BSE agent in tissues is generally determined by injecting animals, usually mice, with material believed to be infected with BSE, then observing the mice to see if they die and have characteristic brain tissue changes. Mouse inoculation studies take a long time (up to 700 days) to detect the agent, and a negative result (that is, lack of brain tissue changes in the injected mice) may only mean that there was too little of the infectious agent to cause symptoms, not that the material was really free of the infectious agent altogether. It is also possible to detect the presence of the abnormal prion protein in tissues (such as brain) using special staining procedures although these methods do not allow an accurate assessment of infectivity of the infected material.
Does BSE or a similar disease occur in humans?
BSE belongs to a group of progressive degenerative neurological diseases known as transmissible spongiform encephalopathies (TSEs). TSE diseases are always fatal. The TSE diseases include scrapie, which affects sheep and goats; transmissible mink encephalopathy; feline (cat) spongiform encephalopathy; and chronic wasting disease of deer and elk. There are six TSE diseases that affect people: kuru, classical Creutzfeldt- Jakob disease (CJD) and variant Creutzfeldt-Jakob disease (vCJD), Gerstmann-Str?ussler-Scheinker syndrome, fatal familial insomnia, and sporadic fatal insomnia. The human diseases are very rare; for example, classical CJD has been well studied and occurs sporadically worldwide at a rate of about one case per one million people.
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Questions and Answers on Variant CJD (VCJD)
What is the new variant form of CJD that the experts in the United Kingdom believe might be related to the BSE outbreak in cattle?
In contrast to the classic form of CJD, the new variant or variant form (vCJD) in the United Kingdom and France affects younger persons (average age at onset: 28 years), and has different clinical features from CJD. People with vCJD begin with serious psychiatric problems or problems with their senses (ears, eyes or smell). This first set of symptoms is followed weeks or months later by poor muscle coordination, problems with muscle spasms, and mental confusion; these patients also have abnormal electroencephalograms (EEG). The illness lasts for at least 6 months, but most people die approximately 13 months after their symptoms begin. When patients?brains are examined by autopsy, there are clear changes in brain tissue structure, including many "spongiform," or open spongy-looking areas, abnormal spots of prion protein called plaques, and other areas with much prion protein accumulation.
Exactly how does this newly recognized variant of CJD differ from classical CJD?
In 1996 the Spongiform Encephalopathy Advisory Committee (SEAC) of the UK announced the identification of 10 cases of variant CJD (vCJD, Lancet, 1996, 347: 921-25). The following features describe how vCJD cases differ from the sporadic or classical form of CJD:
The affected individuals were much younger than the classical CJD patient. Typically, CJD patients are over 63 years old. The average patient with vCJD is 28 years old; patients ranged from 12-52 years old.
The course of vCJD averaged 13 months. Classical CJD cases average a 6 month duration.
In the vCJD cases, electroencephalographic (EEG) electrical activity in the brain was not typical of classical CJD.
Although changes in brain tissue structure of patients with vCJD were recognizable as CJD, the pattern was different from classical CJD, with large aggregates of prion protein plaques often surrounded by vacuoles.
How did people get this new variant of CJD?
On March 20, 1996 a statement from the Spongiform Encephalopathy Advisory Committee (SEAC) of the United Kingdom indicated concern that before November 1989, when inclusion of certain cow and sheep by-products in human food was banned, the BSE agent may have been transmitted to people through contaminated food products. The SEAC said that food might account for the 10 vCJD cases described in April, 1996 in the medical literature (Lancet 1996; 347:921-5). The specific foods, if any, that may be associated with the transmission of this agent from cattle to humans are unknown. However, the SEAC has indicated that milk and milk products are unlikely to pose any risk for human exposure to the BSE agent.
What is the evidence directly linking this newly recognized variant of CJD to BSE exposure?
There is strong epidemiologic and laboratory evidence suggesting that new variant CJD (vCJD) and BSE are caused by the same infectious agent. For instance, there have been no confirmed cases of vCJD in other geographic areas where there have been no BSE cases. In addition, the time interval or "incubation period" between the most likely period for the initial exposure of the population to potentially BSE-contaminated food (1984-1986) and onset of initial vCJD cases (1994-1996), about 10 years, is similar to the known time intervals between exposure to the classical CJD agent and the development of CJD. An experimental study reported in June 1996 showed that three cynomologus macaque monkeys that were injected with brain tissue from cattle with BSE later developed symptoms and changes in brain tissue that were strikingly similar to vCJD (Nature 1996;381:743-4). Another study published in 1996 showed that prions obtained from 10 vCJD patients and BSE-infected animals had molecular characteristics that were similar to each other but that were distinct from prions obtained from patients with classical CJD (Nature 1996;383:685-90). Furthermore, intermediate results of an ongoing experimental study involving injection of a panel of mice with the agent that causes BSE and vCJD suggest that these agents cause a similar disease in mice (Nature 1997;389:498-501). A recent study using transgenic mice (PNAS 1999; 96:15137-15242) supports the hypothesis that the BSE agent from cattle causes vCJD.
How many cases of variant CJD have occurred?
Cases of variant CJD are very rare, and most have occurred in the United Kingdom. The latest information (October 2, 2000) issued by the Department of Health, United Kingdom (www.doh.gov.uk/cjd/) indicates that there have been 73 confirmed cases of vCJD in the United Kingdom. These cases have all been diagnosed since 1995. France has reported two cases. The Republic of Ireland reported one case in 1999. No cases have been recognized in other European countries, or in the United States
Could anyone in Europe diagnosed with the newly recognized variant of CJD (vCJD) have acquired this from vaccines?
In the UK the majority of cases of vCJD were born before 1980, and it is very unlikely that they received vaccines contaminated with the BSE agent (Vaccine 2000 19:409-410). Surveillance of vCJD in the UK has identified three "risk factors," or characteristics common to most if not all of the people who had vCJD: i) residence in the UK; ii) a particular genetic susceptibility (met/met homozygosity at codon 129 of the PrP gene); and iii) age. Epidemiological evidence to date suggests that these cases of vCJD acquired the disease from eating beef products containing the BSE agent after 1980. To date (October, 2000) there have been 76 confirmed cases of vCJD. Of these, 73 have occurred in the UK. A case of vCJD was reported in the Republic of Ireland in June 1999 in a person who had been a UK resident from 1989-1995. Two cases of vCJD have been diagnosed in France, one in 1996 and the other in 1999. Neither of these people had lived or traveled in the UK. However, according to data published by the UK (HM Customs and Excise), France was a leading European importer of bovine products during the period 1980-1996. No other cases of vCJD have been found in Europe.
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Questions and Answers on Bovine Derived Materials Used in Vaccine Manufacturing:
Why are animal products used in the manufacture of vaccines?
Vaccines contain either killed or weakened forms of disease-causing bacteria or viruses, or components of these that stimulate a response by the body抯 immune system, which then protects against the development of disease. In the late 19th century, microbiologists began to grow bacteria in the laboratory. The early bacteriologists tried to mimic as closely as possible the infected person抯 tissues by using sugars, salts, and various meat extracts to make "growth media." These kinds of conditions were quite successful in growing bacteria and then viruses in the lab, because these media supplied the many necessary nutrients. Although synthetic media have been developed for growth of many medically important microorganisms, some still require additional nutrients which are easily provided by animal-derived products such as serum and blood.
Which bovine derived materials are used in vaccine manufacture?
Microorganisms for vaccine manufacture are grown under controlled conditions in media which provide the nutrients necessary for growth. Cow components are often used simply because cows are very large animals, and thus much material is available. Animal-derived products used in vaccine manufacture can include amino acids, glycerol, detergents, gelatin, enzymes and blood. Cow milk is a source of amino acids, and sugars such as galactose. Cow tallow derivatives used in vaccine manufacture include glycerol. Gelatin and some amino acids come from cow bones. Cow skeletal muscle is used to prepare certain complex media. Many difficult to grow microorganisms require the addition of serum from blood to the growth media.
Do all bovine materials have the same risk of transmitting the BSE agent?
Scientists have found that different bovine tissues contain different amounts of the BSE agent. It is generally believed that the highest amounts of infectivity are found in the brain and spinal cords from animals in the final stages of clinical disease. Some tissues such as skeletal muscle and milk have never been shown to have any infectivity. However, the slaughtering and butchering methods used to obtain tissues and prepare materials can affect the amount of infectivity that may be present. Also the production processes used to prepare bovine-derived materials (such as heat sterilization and chemical treatment) may reduce or remove infectivity.
What measures have the FDA taken to ensure that people are not exposed to the BSE agent in vaccines?
It is believed that variant CJD was acquired from eating food products containing the BSE agent. However, FDA wants to minimize any chance that the BSE could be introduced into biologic products during manufacture. The Center for Biologics Evaluation and Research (CBER) is responsible for regulation of biologic products, including vaccines. In a 1991 letter to manufacturers CBER expressed concern about bovine sourced material. In December 1993 and May 1996 FDA issued letters advising that bovine derived materials from animals born in or residing in countries where BSE had occurred should not be used to manufacture FDA-regulated products intended for administration to humans. A 1993 Points to Consider document ("Points to Consider in the Characterization of Cell Lines Used for the Production of Biologics") stressed the importance of control of sourcing of bovine materials. On April 19, 2000, CBER issued a letter reminding manufacturers that the USDA list of BSE-countries had been expanded to include not only those countries where BSE was known to exist but also those where BSE may exist (FR, January 6, 1998). CBER strongly recommended "that manufacturers take whatever steps are necessary to assure that materials derived from all species of ruminant animals born, raised or slaughtered in countries where BSE is known to exist, or countries where the USDA has been unable to assure FDA that BSE does not exist, are not used in the manufacture of FDA-regulated products intended for administration to humans."
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Questions and Answers Related to FDA Guidance on Sourcing of Bovine Materials:
How did the FDA discover that some manufacturers are not universally following letters, PTC and guidance documents?
During review of new license applications manufacturers are asked to provide detailed descriptions of the manufacturing process and documentation of source country for all materials of animal origin. During review of a recent license application it was determined that some of the material used during manufacture had been obtained from countries which are on the USDA list of countries which either have or may have BSE. This finding prompted an inquiry of all licensed vaccines.
What is FDA doing now to assure that companies follow guidance, letters, and PTC documents?
The Center for Biologics Evaluation and Research (CBER) has asked licensed vaccine manufacturers to evaluate all bovine sourced material used at any stage of manufacture. Manufacturers have been requested to identify all material of animal origin. For materials of bovine origin CBER has asked manufacturers to identify the source country from which the animals originated, the date the material was obtained and the date the material was used in manufacture of vaccine lots.
When it is determined that any bovine-derived component used to make the working seeds or during routine production was obtained from a country on the current USDA list of countries which either have or may have BSE, the manufacturer has been asked to change the source of such material. CBER inspects vaccine manufacturers on a routine basis to determine whether sourcing and documentation are consistent with current recommendations contained in letters and guidance documents.
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Questions and Answers Related to Vaccines and vCJD:
Why did the FDA ask the Transmissible Spongiform Encephalopathy Advisory Committee and the Vaccines and Related Biological Products Advisory Committee meet on July 27th, 2000?
The Center for Biologics Evaluation and Research (CBER), FDA regulates biological products including vaccines. For several years CBER has recommended that bovine derived components from countries which have or may have BSE (bovine spongiform encephalopathy, the so called "mad cow disease") not be used for the manufacture of US-licensed biological products including vaccines. The consumption of food contaminated with the BSE agent has been linked to a fatal disease in people called new variant or variant CJD (vCJD). There is no evidence that any case of vCJD has resulted from use of a vaccine, and there is no evidence that any vaccines harbor the BSE agent. CBER had recently determined that some vaccines were manufactured using bovine components from countries which the USDA has determined have or may have BSE. CBER believed that the chance of getting vCJD through vaccines is remote and theoretical. However, CBER has responsiblility to ensure that vaccines used in the US are safe and asked for this special joint meeting to ask vaccine and TSE experts to formally discuss the risk of transmitting vCJD from vaccines.
What is the chance/risk that a vaccine on the market in the US contains the BSE agent?
Studies of the BSE agent have shown that infectivity depends on nature of material used, how much is used and the route of administration. Other factors, such as the country of origin of the cattle used to supply the manufacturing material, also have to be factored into any risk estimate. Both the European Community and the US Pharmaceutical industry have presented risk assessment calculations which attempt to account for all these factors. In 1999, the Council on Scientific Affairs (CSA) of the American Medical Association considered the risk of BSE to public health and determined that the current risk of transmission of BSE in the US is minimal, concluding that adequate guidelines exist to prevent high risk bovine materials from contaminating products intended for human use. The report from the CSA did not address the possibility that regulated industry might not follow all of the recommendations made by the FDA. However, both FDA and the joint advisory committee meeting have considered the risks posed by bovine material in vaccines and concluded that any risk is remote and theoretical See Section VI and MMWR Recommendations and Reports.
What is the risk of getting vCJD if a vaccine contained the BSE agent?
There is no evidence to date that vaccines have contributed to the cases of vCJD seen in Europe. Nor is there evidence that any vaccines harbor the BSE agent. Vaccines are given a very limited number of times via the intramuscular, subcutaneous or oral route. Even in experimental studies, these routes of administration are less effective at spreading the agent than the intracerebral route usually used to assess infectivity in animal studies. The amount of infectivity present and the efficiency with which the BSE agent passes from cow material to humans will also affect the likelihood of infection.
How did FDA derive its risk estimates and decide the risk of vCJD from vaccines was remote and theoretical?
Scientists, regulatory authorities in Europe and the pharmaceutical industry of the US have considered the risks of BSE in pharmaceutical products. In estimating these risks it is necessary to consider the country of origin of any bovine material, the type of bovine tissue used, the steps used to process the bovine tissue, the amount of bovine derived material used and the stage of vaccine manufacture at which the bovine material is used. Using previously published methods for calculating theoretical risk of cases of vCJD from pharmaceutial products, FDA has calculated a conservative estimation of the risk of a vaccine causing a case of vCJD. These estimates were presented in public session at the joint advisory committee on July 27th 2000. FDA believes these estimations are a realistic worst case scenario and that the real risk any US licensed vaccine could cause vCJD is even lower than the estimates presented. See Section VI and Section II.
Why is FDA leaving vaccines on the market that did not follow its own recommendations regarding sourcing of bovine derived materials?
The FDA has looked at the benefit of vaccines and the risk of vCJD from vaccine use. Vaccines have a proven benefit in reducing the incidence of serious, often life-threatening diseases. The Public Health Service, FDA, and the members of FDA抯 advisory committees on TSE and Vaccines and Related Products (VRBPAC) (7.27.00 link to Ad Com transcripts, link to AAP and ACIP) believe the risk that anyone will get vCJD from a vaccine to be remote and theoretical. Without routine vaccination the incidence of disease would increase. This was seen in Sweden, Japan and the UK when the number of children vaccinated against pertussis decreased due to concerns about vaccine adverse events associated with the whole-cell DTP vaccine. Manufacturers of US licensed vaccines ensure an adequate supply of recommended vaccines. Removal of a licensed vaccine from the market could cause insufficient supply and potentially increase the number of unvaccinated or under vaccinated individuals at risk from preventable diseases.
If vaccines are safe why did the UK recall their polio vaccine?
If vaccines are safe why did the UK recall their polio vaccine? The UK recalled the Evans/Medeva Oral Polio Vaccine in October, 2000. This vaccine has never been licensed for use in the US. The Medicines Control Agency (MCA) had requested and received assurances from drug companies that they were implementing guidance not to use UK-sourced bovine materials in the manufacture of injectable medicinal products. The recall was prompted by evidence that the Evans/Medeva vaccine was manufactured using fetal calf serum from the UK at a time when there was a risk of BSE in that country. This is in contravention of European Union guidelines. According to a statement from the Chief Medical Officer at the UK Dept. of Health (10.20.00) the company had assured the MCA of the UK that UK-sourced bovine materials were not used in the manufacture of the vaccine. However, these assurances were inaccurate, thus the vaccine was withdrawn. (www.doh.gov.uk/cmo/cmo00_12.htm) What is the recent concern in the Republic of Ireland about polio vaccine and vCJD?
In December, 2000 the Irish Government issued a statement indicating that an oral polio vaccine distributed in 1998 and 1999 in Ireland had been manufactured using human serum albumin from a pool of donors, one of whom had since been diagnosed with vCJD. Evans/Medeva manufactured this oral polio vaccine. This vaccine is not licensed for use in the US.
Have there been vaccines produced using cow materials from countries where there is a significant risk of BSE?
During review of a new license application, FDA learned that one manufacturer had used bovine-derived material from a country in which the USDA had determined that BSE might exist. CBER requested all vaccine manufacturers review the source of any bovine derived material used in the manufacture of their vaccines. Additional vaccines manufactured using bovine derived products from European countries were identified. These vaccines are identified in the 揜ecommendations for the Use of Vaccines Manufactured with Bovine Derived Materials?section of this web site.
Is there a possibility that some vaccines might be contaminated with the BSE agent? (See above 揥hat is the chance/risk that a vaccine on the market in the US contains the BSE agent?
My child was just immunized. Should I be worried?
No. FDA and other Public Health Service agencies believe that the risk of contamination of any US licensed vaccine with the BSE agent is remote and theoretical. FDA asked a special joint meeting of the Transmissible Spongiform Encephalopathy and the Vaccines and related Biological products Advisory Committees to review the available vaccine risk and benefit information. This joint committee concluded that the substantial risk of disease due to not vaccinating children far outweigh the theoretical risk posed by vaccines that have a remote chance of containing the BSE agent (see PHS statement in MMWR and 揜ecommendations for the Use of Vaccines Manufactured with Bovine Derived Materials?section of this web site for details)
Why are you continuing to vaccinate children with a vaccine that may be contaminated with BSE causing materials? Also see above 揥hy is FDA leaving vaccines on the market that did not follow its own recommendations regarding sourcing of bovine derived materials."
FDA and other Public Health Service agencies believe that the risk of contamination of any US licensed vaccine with the BSE agent is remote and theoretical. FDA asked a special joint meeting of the Transmissible Spongiform Encephalopathy and the Vaccines and related Biological products Advisory Committees to review the available vaccine risk and benefit information. This joint committee concluded that the substantial risk of disease due to not vaccinating children far outweigh the theoretical risk posed by vaccines that have a remote chance of containing the BSE agent (see PHS statement in MMWR and Recommendations for the Use of Vaccines Manufactured with Bovine Derived Materials?section of this web site for details)
What is being done to ensure the United States?vaccine supply is safe?
Also see above 揥hat is FDA doing now to assure that companies follow guidance, letters and PTC documents??/em> FDA and the other PHS agencies believe that vaccines licensed for use in the US are safe and effective. However, because even the perception of risk could have negative consequences for the use of vaccines and because it is possible to decrease the risk of an already safe product even further, manufacturers of affected vaccines have agreed to change the source of the bovine derived material used during production of the working seeds and cell banks and for routine production (see Recommendations for the Use of Vaccines Manufactured with Bovine Derived Materials" section of this web site for details).
When will vaccine manufacturers finish replacing cow-derived materials in vaccines with materials obtained from countries free of BSE?
The time to make a vaccine and bring it to market can take several months to a year. Most vaccine made using bovine derived material from non-BSE risk countries should be available by the end of 2001.
Shouldn't all potentially contaminated vaccine be destroyed?
Also see above 揥hy is FDA leaving on the market vaccines which may be contaminated with the BSE agent??/em> FDA and other PHS agencies believe that the vaccines currently licensed for use in the US are safe. A special joint meeting of the TSE and Vaccines and Related Biological Products Advisory Committees concluded that the real risk of disease due to not vaccinating far outweigh the theoretical risk posed by exposure to vaccines that have a remote chance of containing the BSE agent.
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