Pig Virus DNA Found in Merck’s Rotavirus Vaccine

DNA from two types of pig virus have been detected in samples of Merck & Co.’s <"http://www.yourlawyer.com/topics/overview/rotateq">RotaTeq vaccine. According to The Wall Street Journal, one of the pig-virus types found in the Merck vaccine is the same one found in GlaxoSmithKline’s Rotarix vaccine in March.

Both RotaTeq and Rotarix protect infants against rotavirus, which causes severe dehydration and diarrhea. It is estimated that more than 500,000 deaths in infants worldwide each year are the result of rotavirus. According to the Centers for Disease Control, as of June, 2009, about 72 percent of U.S. infants five months of age had received at least one dose of rotavirus vaccine.

In March, the Food & Drug Administration (FDA) told doctors to stop using Glaxo’s Rotarix after it was fund to contain a pig virus called porcine circovirus 1, or PCV1. The discovery of this virus was made by an independent U.S. academic research team, using a novel technique that revealed DNA from PCV1 in Rotarix. Follow-up tests by GlaxoSmithKline and FDA scientists confirmed the academic team’s findings and confirmed that viral components have been present since the early stages of the vaccine’s development, including during clinical studies.

At the time, the FDA said PCV1 is not known to cause illness in humans, and no adverse effects have been observed in children vaccinated with Rotarix. But because the agency’s investigation was ongoing, doctors were advised to use Merck’s RotaTeq vaccine.

Now, Merck says its own testing has identified fragments of DNA from PCV1 and from a related porcine circovirus, PCV2. Again, neither of these viruses is known to cause illness in humans. The source of the virus DNA is not yet known, but according to the Journal, there is some suspicion that it may have come from trypsin, an enzyme derived from pigs that’s used in the manufacture of the vaccines.

According to The Wall Street Journal, the FDA has not immediately said whether RotaTeq should be avoided because of the presence of the pig virus DNA. The agency had scheduled a meeting today to discuss Rotarix vaccine. The advisory panel will now discuss both vaccines and whether pig viruses pose risks to humans.

This is not the first time rotavirus vaccines have caused concerns. In 2007, the FDA warned that RotaTeq had been associated with a serious side effect called intussusception – a twisting or obstruction of the intestines that can be fatal. At the time, the agency said it had received reports of 28 cases of intussusception between February 3, 2006 through January 31, 2007 in infants who received RotaTeq.

In 1999, Wyeth was forced to pull its rotavirus vaccine from the market due to similar concerns about intussusception.

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