An important privilege pharmacists have is to administer and counsel patients about vaccinations they should receive. A relatively new (new meaning it’s been on the market for roughly 10 years) but very important vaccine called Gardasil is a vaccine that protects patients against multiple strains of the human papillomavirus virus (HPV). HPV is an STD virus that can cause genital warts, cervical cancer (only in women), anal cancer, throat cancer, and penile cancer (only in men). HPV is spread through skin-to-skin contact, especially when mucous membranes come into contact with each other (e.g. kissing, intercourse, and oral sex). Most people in the United States contract some form of HPV in their lifetime, and a person usually contracts it by the age of 26 years. The Gardasil vaccine, also known as quadrivalent human papillomavirus vaccine (HPV4), is recommended as a 3-dose series administered at 0, 1–2, and 6 months. The vaccine is administered to both boys and girls, and it is recommended to be administered to children between the ages of 9 and 13 years. The reason for administering the vaccine to children at such a young age is because there is a high chance that they will contract some form of HPV during their teenage or young adult years through skin-to-skin contact. The vaccine can be administered to girls between the ages of 9 and 26 years, and it can be administered to boys between the ages of 11 and 21 years (boys between the ages of 21 and 26 years can be given the vaccine under the special circumstances of engaging in male-male sexual activity or if they have a suppressed immune system).
The purpose of this study was to asses if administering doses 2 and 3 of the Gardasil vaccine later than recommended would affect antibody titers. The reason for this study is that the Gardasil dosing schedule is often not followed, and children/adolescents often receive doses 2 and 3 later than recommended. The study assessed antibody titers to HPV4 when dose 2 and/or dose 3 were administered on schedule or delayed. 331 Healthy females aged 9–18 years were enrolled at the time of receipt of HPV4 dose 2 or 3. Participants were classified as belonging to one of four groups depending upon timing of receipt of HPV4: both doses on time; only dose 2 delayed later than 90 days; only dose 3 delayed later than 180 days; or both doses 2 and 3 delayed. Pre- and post-dose 3 blood samples were taken to test HPV antibody titers.
The results of the study were that post-dose 3 geometric mean titers (GMTs) for all HPV types were NOT significantly lower for any of the delayed dosing groups when compared to the on time group. When compared to the on time group, the post dose 3 GMTs in the delayed dose 3 group were actually significantly higher for HPV types 6, 11, and 16. These results suggest that delays of dose 2 or 3 do not interfere with immune responses to the vaccine after completion of the 3-dose series. These results are important because they support current recommendations to not administer additional doses of HPV4 vaccine if dose 2, dose 3, or both doses have been administered late.
I think this study highlights an important factor in vaccinations that we as pharmacists will have to be aware of, which is inappropriately administering a repeat vaccination. This study proves the importance of checking a patient’s antibody titer before administering a repeat dose of a vaccine. We should never assume that a patient’s antibody is low because the vaccine was not administered in the correct timeline or certain recommendations assert that vaccines given during a specific time period need to be readministered. As pharmacists, we will need to use our analysis skills to determine which vaccines our patients need and which vaccine antibodies should be tested via titers before readministering any vaccines.
My question posed to colleagues: How do you think this study applies to pharmacists administering and recommending vaccinations? Are the results of this study surprising to you?
Russel, K, Dunne, EF, Kemper, AR, et al. Antibody responses among adolescent females receiving the quadrivalent HPV vaccine series corresponding to standard or non-standard dosing intervals. Vaccine. 2015;33:1953-1958.