Scandinavia study finds HPV vaccine safe

In a large study of nearly a million girls in Denmark and Sweden, the human papillomavirus vaccine was not linked to short- or long-term health problems.

The HPV vaccine, given in three doses over a period of six months to boys and girls around age 12, protects against infection by a virus that can cause cervical cancer.

"There were not really any concerns before our study and no new ones after," Lisen Arnheim-Dahlström said. She led the study at the Karolinska Institutet in Stockholm.

The new study used national data from both countries to investigate how many girls ages 10 to 17 were diagnosed with any of 53 autoimmune or neurological problems, including celiac disease, pancreatitis, rheumatoid arthritis, psoriasis and narcolepsy. It also looked at whether girls developed blood clots shortly after vaccination.

More than 997,000 girls were diagnosed with the conditions on the list between 2006 and 2010 and more than 296,000 of them had received at least one HPV vaccine dose. Some 160,000 girls had received all three doses.

According to the results published in BMJ, there was no link between the type or timing of the girls' health problems and whether they had gotten the vaccine within the previous six months or had ever received the vaccine.

Previously, isolated incidents of blood clots or other problems had been pegged to the vaccine, but this large new study did not find any negative health consequences, researchers said.

The responsibility for safety is highest when you're giving a drug to people who are well, said Dr. Mark Schiffman, a senior investigator at the National Cancer Institute who was not involved in the new study.

Though his research centers on cervical cancer, Schiffman himself was a "late adopter" of the HPV vaccine. He told Reuters Health he did not have his young daughter vaccinated when the shots were first approved.

This large cohort study found no evidence supporting associations between exposure to qHPV vaccine and autoimmune, neurological, and venous thromboembolic adverse events. Although associations for three autoimmune events were initially observed, on further assessment these were weak and not temporally related to vaccine exposure. Furthermore, the findings need to be interpreted considering the multiple outcomes assessed.

Drug approval trials are often too small to detect whether a dose given to millions of people might negatively affect one or two, he said. Those kinds of small associations can only be found after the drug has been used in a large population.

More than 100 million doses have been administered worldwide since the first HPV vaccine was approved in 2006.

"I'm now convinced," Schiffman said. "I recommend to other near and dear friends and family that the vaccine is, to my mind, safe."