Saar Kuzi
Alessandra Coutinho Fernandes
William Cope
Richard Tapping
Kashif Ahmad
Reda Sadki
Shubhra Kanti Karmaker Santu
Adam P Rusch
Elizabeth Edwards
Matthew LawFA16 Immunization Module’s Updates
HPV Vaccine: Immunogenicity of 2 doses in Girls vs 3 doses in Young Women
As mentioned in an earlier update by @Angela Delano, there is a significant compliance issue with the completion of the recommended three doses of the HPV vaccine.The following summarizes an article addressing the effectiveness of 2 doses vs 3 doses.
Human papillomavirus (HPV) has been identified as a cause of cervical cancer, with the HPV genotypes 16 and 18 accounting for approximately 70% of cervical cancer cases. There are two types of vaccines: the bivalent (HPV-16 and HPV-18) and quadrivalent (HPV-6, HPV-11, HPV-16, and HPV-18) vaccine, which are both given at 0, 2, and 6 months.
This study focused on whether 2 doses of the quadrivalent vaccine given in girls ages 9-13 produced a similar immune response to a 3 dose regimen given to young women ages 16-26.
Importance: This may help to improve the rates of compliance by alleviating the financial burden of paying for the vaccine and improving the convenience of getting the vaccine. Studies with a similar goal have led to reduced-dose schedules for hepatitis B, pneumococcal, and meningococcal serogroup C vaccine programs.
Results: The study measured titer levels and confirmed that 2 doses of the quadrivalent vaccine given in girls ages 9-13 produced a statistically noninferior immune response to a 3 dose regimen given to young women ages 16-26.
However, the immune response for one of the high-risk strains (HPV-18) was not equivalent when comparing girls of the same age group (9-13). When comparing girls who received 2 doses vs girls who received 3 doses at the 2-year mark, the 2 dose regimen resulted in an inferior immune response to HPV-18 compared to the 3 dose regimen.
Interestingly, when the 9-13 age group was given a third dose at the 6th month, their immune response was statistically superior to that of the 16-26 age group, who were also given the three doses. This may be due to the age-dependent difference in B-cell memory formation.
Unfortunately, the need for additional doses later in life is still unknown (efficacy has only been studied for 60 months). Because the threshold level of antibodies needed for protection has not been established, the question of durability cannot be answered. Therefore, additional research must be done to approve the use of a reduced-dosing schedule in girls.
http://jama.jamanetwork.com/article.aspx?articleid=1682939
@ Brittany Lala Thank you for posting this article summary. The results of this study were very intriguing. As more research is conducted, it will be interesting to see if the data favors the transition to two doses, which certainly would improve compliance. Did the authors of the paper offer any insight as to why only the immune response to HPV-18 was variable with dosage in the 9-13 age-group versus the other strains (i.e. HPV-16)?
This was the first vaccine intended to prevent cancer. An amazing success story!
Once more research comes out on the long term efficacy of the two dose plan, I think that this would be very beneficial. (Assuming the research results are in favor). Any time you can prevent a visit to a clinic for a vaccine you're going to improve compliance.