Monday, October 25, 2010

Why I chose Cervarix...

At present, there are 2 vaccine against Cervical Cancer. Cervarix, by GSK, and Gardasil by MSD.
Now, one claims to be a tetravalent vaccine,which means it provide protection against 4 genotype of HPV(Human Papilloma Virus) that is responsible in triggering cellular changes that leads to cervical cancer.
One thing that is rather misleading is the claim that Gardasil being emphasized upon as a tetravalent vaccine in protecting against Cervical cancer. This is such a misleading statement. Indeed while Gardasil being a tetravalent vaccine by it's own rights does not mean it provide more protection compared to Cervarix.
Tetra- 4, the subtypes are 6,11,16,and 18
Subtype 6 and 11 causes only genital warts, and does not lead to Cervical cancer per se.
While on the other hand, Cervarix, was designed to protect against subtype 16, and 18, it however, have shown to provide cross protection against subtype 31,33, and 45.
Subtype 16,18,31,33,45 are the top 5 serotype that causes cervical cancer.
Cervarix was designed with ASO4 as an adjuvant, acting as "turbocharger" that leads to high level of antibody titre and for prolonged period of time. Mathematical formulation ha estimated that Cervarix gives protection for at least 20 years, while antibody level of Gardasil would dwindle after the 5th year after vaccination.
One of the criteria for one to develop cervical cancer would be persistent infection with HPV.
What happens then for those who was vaccinated with Gardasil after 5 years. Nobody today can tell whether the need of a booster. Though the blood antibody titre may be low, or even absent, but the B-memory cell would trigger the production of these antibodies. True. But it fails to serve its purpose as it takes 2 days for these antibodies to be produced, while it takes only 2 hours for HPV in blood circulation embed themselves at the basal membrane, isolating them from the circulating antibodies.
It  got on my nerves when I got to know that there are doctors who told the patient to chose the vaccine of their liking. Doctors are humans with their fair share of doubts. I personally emailed Dr Diane Harper, the principal researcher in both vaccines, and a committee member in WHO,
her reply is this:-
For a virus that stays dormant in the body for decades, one needs a vaccine that last much longer than the virus for which the vaccine is designed to protect against.

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