Merck's Gardasil deemed safe in another large study

Relax, parents, vaccine researchers say. Merck's ($MRK) human papillomavirus vaccine has proven safe in another large study designed to gauge its side effects. Required by regulators in the U.S. and Europe, the study flagged a couple of reactions, but its lead author called the findings "very reassuring."

After looking at Kaiser Permanente records on 190,000 females, Nicola Klein, co-director of Kaiser's Vaccine Study Center, and her team concluded that patients were 6 times more likely to faint the day of the shot than during ensuing weeks, and about 1.8 times more likely to see a skin or subcutaneous infection at the injection site.

Recommended by the Centers for Disease Control and Prevention, and required in many states, Gardasil has been controversial almost since its debut in 2006. FDA-approved to prevent cervical cancer (among other things, these days), the shot seemed like a no-brainer to some in public health. But because it staves off HPV infection, transmitted via sexual contact, its use in young girls--required to ensure protection from the virus--drew criticism.

Merck had big hopes for the product, but partly because of the controversy, sales have lagged expectations. The company has been racking up new indications in an effort to broaden use--and boost revenues. So far, that appears to be working; Gardasil sales grew by 22% last year, to $1.2 billion. Also, the CDC has now recommended it for use in boys as well as girls.

This is the second study in a year's time to find no links between severe adverse events and Gardasil use. The previous study, published last year, found no increased risk of fainting, either. The latest research found that convulsions and epilepsy reported in Gardasil patients weren't linked to the shot; the board investigated 14 deaths and concluded they weren't associated with the vaccine, either.

As Bloomberg notes, the Kaiser researchers say their study may have missed "very rare conditions" linked to Gardasil. Critics have said that long-term side effects could still arise, and that these shorter-term studies aren't enough. Merck is on the hook for another long-term study, this time looking at efficacy, and for a short-term safety study, both required by FDA.

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