Benefits of Contaminated Rotavirus Vaccine Outweigh Risks, Says FDA Panel

May 07, 2010

May 7, 2010 — A majority of an advisory committee for the US Food and Drug Administration (FDA) today voiced support for the continued use of a contaminated rotavirus vaccine now under FDA suspension, arguing that the vaccine's benefits far outweigh the theoretical risks of the contaminant.

However, members of the Vaccines and Related Biological Products Advisory Committee also recommended studies of possible long-term risks of the vaccine in question, GlaxoSmithKline's Rotarix.

"On the whole, the vaccine seems to have a spectacular record for safety and efficacy," said committee member John Coffin, PhD, professor of molecular biology and microbiology at Tufts University in Boston, Massachusetts. "The loss of the vaccine would be devastating. But we need to clean it up as soon as possible."

"The benefits are so big the risks would have to be enormous to outweigh them," added Harry Greenberg, MD, senior associate dean for research at Stanford University School of Medicine in California. "So far, we see only theoretical risks."

In March, the FDA recommended that clinicians stop using Rotarix after it discovered that the vaccine contained DNA sequences from a virus found in pigs called porcine circovirus 1 (PCV1). The virus is not known to cause disease in either pigs or humans, according to the FDA.

The FDA later learned that another rotavirus vaccine on the market, Merck's RotaTeq, contains DNA fragments of both PCV1 and a related virus called PCV2. The latter virus can cause a wasting disease in pigs, but as with PCV1, there is no evidence it causes illness in humans, according to the FDA, which has yet to announce any action on the Merck product.

Representatives of GlaxoSmithKline told the advisory committee today that the company is committed to ridding Rotarix of PCV1, but that it would take several years to do so, considering the complexities of the manufacturing process.

Committee Members Have More Worries About PCV2

While the advisory panel did not find PCV1 to be any kind of short-term threat to humans, various members expressed apprehensive about PCV2, a contaminant in RotaTeq. Gordon Allan, PhD, a professor at The Queens University Belfast in Belfast, Northern Ireland, rang an alarm bell with what resembled a passing remark about how the virus triggers postweaning multisystemic wasting syndrome.

"PCV2 in a lot of ways is a strange virus," Dr. Allan said. To get "good disease in pigs with PCV2," one must infect them with the virus and then stimulate their immune system, either by reinfecting them with the virus or vaccinating them. He raised the possibility of this chain of events occurring with sequential doses of rotavirus vaccine.

Dr. John Coffin also advocated for more study of PCV2. "I have some nervousness about that one as well," he said.

Communicating the risks of the 2 rotavirus vaccines to the public promises to be tricky, he added. "It will be hard to explain in this general era of antagonism toward vaccines."

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