Parents' worries raise hurdles for Merck, GlaxoSmithKline HPV shots

Merck ($MRK) and GlaxoSmithKline ($GSK) have some persuading to do. A growing share of U.S. parents say they won't vaccinate their daughters against human papillomavirus, which causes cervical cancer. And that leaves Merck's Gardasil and GSK's Cervarix with a shrinking market.

According to a survey released in the journal Pediatrics, some 40% of U.S. parents were against HPV vaccination in 2008. By 2012, the share of parents who wouldn't use the vaccine grew to 44%. "That's the opposite direction that rate should be going," Mayo Clinic pediatrician and researcher Robert Jacobson said in a statement. "HPV causes essentially 100% of cervical cancer and 50% of all Americans get infected at least once."

About 1 in 6 parents worry that the vaccines aren't safe, Bloomberg notes. That's despite studies that have shown HPV shots aren't linked to serious side effects--and do protect against cancer. Another big problem: Parental worries about encouraging teen sex--or lack of worry that their children might become sexually active soon.

Some media reports seem to have outweighed the safety data, said one researcher who wasn't involved in the Pediatrics study. "There were a lot of very sensationalized anecdotal reports of (girls) having bad reactions to the vaccine," Dr. Amanda Dempsey, a University of Colorado Denver pediatrician, told Reuters. "Safety concerns have always risen to the top of the pile, in terms of being one of the main reasons people don't get vaccinated, which is unfortunate because this is one of the most well-studied vaccines in terms of safety and is extremely safe."

Both Merck and GSK have had high hopes for their HPV shots. Cancer-preventing vaccines seemed like a no-brainer, and each product was expected to deliver blockbuster-level sales. But even now, the survey shows, only about one-third of eligible girls have received the vaccine.

Can the drugmakers turn the story around? One thing that researchers pointed out was that pediatricians often aren't recommending the shots to their patients. If Merck and GSK could persuade more doctors to speak up for HPV vaccination, then parents might listen. At least theoretically.

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