January 06, 2015
By Will Boggs MD
NEW YORK (Reuters Health) - Immunization with the quadrivalent HPV vaccine is not associated with an increased risk of multiple sclerosis (MS) or other demyelinating diseases of the central nervous system, researchers from Scandinavia report.
"In a study of almost four million Danish and Swedish women, vaccinated women were diagnosed with demyelinating diseases to the same extent as comparable unvaccinated women," Dr. Anders Hviid, from Statens Serum Institute, Copenhagen, Denmark, told Reuters Health by email. "Some will develop these debilitating diseases after vaccination, not as a result of vaccination per se, but rather due to chance or other causes."
Social and news media have reported numerous cases of MS that developed after HPV vaccination, but the few published studies have found no increased risk of MS or other demyelinating diseases after HPV vaccination. These studies, though, have had limited statistical power, the researchers write.
Dr. Hviid's team used data from Denmark's and Sweden's national vaccination databases and prescription drug registries, which cover all inhabitants of those two countries, to investigate the risk of MS and other demyelinating diseases of the central nervous system following quadrivalent HPV vaccination.
The registries included more than 3.98 million girls and women, of whom 789,082 were vaccinated during the period. Follow-up amounted to more than 21 million person-years.
The risk of developing MS did not differ significantly between vaccinated and unvaccinated periods (6.12 vs 21.54 events/100,000 person-years), according to the January 6 JAMA report.
Similarly, the researchers found no significant difference in the composite outcome of other demyelinating diseases between the vaccinated and vaccinated periods (7.54 vs 16.14 events/100,000 person-years).
"Given the upper limits of the confidence intervals," the researchers say, "the study can exclude a potential 16% increased risk of multiple sclerosis and a 27% increased risk of other central demyelinating diseases."
"In this the largest and most comprehensive study to date, there was no support for this particular safety concern," Dr. Hviid said. "The current evidence suggests that clinicians and patients should not fear demyelinating diseases as a result of HPV vaccination."
"Vaccine safety issues continue to arise," he said. "To maintain professional and public trust in routine immunization programs, it is important to address these issues in a timely manner with high quality research."
Dr. Paolo Pellegrino from University of Milan in Italy has investigated the association of HPV vaccination with various inflammatory and autoimmune conditions. He told Reuters Health by email, "The temporal relationship between HPV immunization and symptom onset does not provide evidence about causality relationship. In addition, the population in study (young women) have a higher risk of developing MS; thus, HPV vaccination may casually occur closely to symptom onset in a patient who was developing MS independently of vaccination."
"Concerns about the possible adverse reactions to vaccination occur on a regular basis in the public opinion," Dr. Pellegrino said. "Considering the public health importance of preventing HPV infection, measures should be taken to dissipate concerns about possible increases in the risk of MS following HPV vaccination."
The study was funded by the Swedish Foundation for Strategic Research, Novo Nordisk Foundation, and The Danish Medical Research Council. Dr Hviid has received a grant from the Novo Nordisk Foundation.
(c) Copyright Thomson Reuters 2015. Click For Restrictions - http://about.reuters.com/fulllegal.asp