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Study Shows Fewer Than Three Doses of Cervical Cancer Vaccine Still Effective

Creatas Images/Thinkstock(COSTA RICA) -- A new study done by the Journal of the National Cancer Institute suggests that even one dose of the human papillomavirus vaccine may be just as effective as the standard three-dose regimen when taking preventive measures against cervical cancer.

The HPV types 16 and 18 are large contributors to the development of cervical cancer, which is the third-most common type of cancer among women. Because the vaccine is typically given in three doses over a 6-month period, it presents a challenge to women because it is expensive and harder to complete. If taking fewer than three doses is still effective, this could mean fewer out-of-pocket expenses and fewer follow-up doctor appointments. If fewer doses are necessary, this could certainly be a motivating factor encouraging more young women to get vaccinated.

In order to determine whether a lower number of doses of the Cervarix vaccine would be effective, Aimée R. Kreimer, Ph.D., of the Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, and a team of researchers conducted an analysis using data from the NCI-sponsored Costa Rica Vaccine Trial. Women there were supposed to receive either three doses of Cervarix or the other control vaccine. However, 20% of these women ended up receiving fewer than three doses due to involuntary factors.

The researchers then compared the frequency of persistent infection with HPV 16 or 18 during four years of follow-up in women who received one or two doses compared to those who received the full three doses. They found similar levels of protection against both types of HPV from the vaccine among women receiving one, two and three doses of the vaccine.

The authors conclude, “Our clinical efficacy data provide suggestive evidence that an HPV vaccine program that provides fewer doses to more women could potentially reduce cervical cancer incidence more than a standard three-dose program that uses the same total number of doses but in fewer women.”

They also added that the evidence presented was surprising, and still caution that it remains to be determined whether fewer than three doses will provide strong protection for substantially longer periods than the 4 years of the current study. 

This study represents a step in the right direction toward more effective and far-reaching cervical cancer prevention. 

Copyright 2011 ABC News Radio

ABC News Radio