Sunday, June 18, 2006

The HPV Vaccine

Good comparative article on Merck's quadrivalent [6, 11, 16, 18] vaccine Gardasil and GlaxoSmithKline's bivalent [16, 18] vaccine Cervarix:

JACKSONVILLE, FLA. - Both vaccines to prevent human papillomavirus infection will be highly effective, Dr. Diane M. Harper said at a conference on STD prevention sponsored by the Centers for Disease Control and Prevention.

Approximately 600 women participated in efficacy studies for a quadrivalent vaccine (Gardasil, Merck), and another 1,100 participated in efficacy studies for a bivalent vaccine (Cervarix, GlaxoSmithKline).

All women were screened at baseline to ensure seronegativity for high-risk strains 16 and 18 of the human papillomavirus (HPV) as well as for strains 6 and 11, which are also included in the quadrivalent product.

"The response was 100% for the bivalent and 89% for the quadrivalent for persistent, vaccine-specific HPV types for those who got the vaccine on time," Dr. Harper said. The recommended regimen for both vaccines is a 0.5-cc injection at 0, 2, and 6 months. In the studies, 94% of participants received all three doses, although not all according to protocol. The off-schedule efficacy was 95% and 89%, respectively, but these differences were not statistically different. "It indicated these will work in a real-world setting," she added.


Both vaccines target high-risk HPV type 16, the type primarily implicated in cervical cancer. Type 16, together with types 18 (also in both vaccines), 31, and 45, account for 81% of cervical cancers, Dr. Harper said. The bivalent vaccine, "although it was designed for 16 and 18, is just as efficacious for HPV 45 and half effective for HPV 31, so that is exciting," said Dr. Harper...


"These vaccines are preventive; they are not therapeutic-that is important to know," Dr. Harper said. "These prevent possible infection by HPV; these are not vaccines that prevent cancer." Because it is important that prevention lasts a long time, the need for a booster shot is anticipated with the bivalent vaccine 7-10 years later, Dr. Harper said. "We don't know if the quadrivalent vaccine will require a booster."


Adverse effects at local injection sites, including pain, erythema, and edema, were similar for both vaccines versus placebo. Other side effects such as headaches, gastrointestinal problems, and fatigue occurred at similar, "acceptable" rates in placebo and vaccine recipients, Dr. Harper said.

Other safety concerns with vaccines include new-onset autoimmune disease and musculoskeletal problems. "We can say no in both cases," she said.

Here's more on the important concept that HPV vaccines are preventive, not therapeutic (paraphrase/translation from medspeak mine):

Antibody production is the primary goal of the prophylactic HPV vaccines. In order to induce the immune system to produce HPV-specific antibodies, you need to stimulate it. [This is what happens with natural exposure to HPV--the virus enters the host's cells, stimulates an immune response, and the body produces antibodies which then clear the infection.] Since HPV, in order to cause infection, must infect actively proliferating and differentiating tissue, HPV cannot be routinely grown in the lab. The technology to produce a "live virus" or "live attenuated virus" vaccine is not available.

So, the next best thing is to use bits of HPV which are still able to stimulate the immune system to produce antibodies. [Hence the designation of HPV vaccines as subunit vaccines.] The HPV vaccines are based primarily on highly immune system-stimulating bits of the HPV outer coat protein [L1 major capsid protein]. The L1 protein self-assembles into virus-like particles (VLPs) that closely mimic the structure of the natural HPV. The VLPs are then able to stimulate the body to produce HPV antibodies.

One important point about VLPs--they do not contain viral DNA. This means VLPs are not infectious, and they have no cancer-producing potential.

Bottom line: HPV vaccines are created from noninfectious virus-like particles (VLPs) of the major capsid protein, L1, that closely mimic natural HPV virions. The vaccines are intended to prevent infection, not treat disease.

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At 3:11 AM, Blogger Virginia-Liberal said...

Hi Ema!

I am on the NVIC mailing list, and today they mailed out a warning that the Gardasil vaccine was not sufficiently tested for safety. Could you comment on it, or do you have any links discussing their claims?

Thank you!

At 4:33 AM, Anonymous Anonymous said...

Speaks volumes to me that no one bothered to comment on this issue.

At 2:08 AM, Anonymous Anonymous said...

safe unsafe, that's right.
no comment. no one knows. not yet.
won't know for about 20 years.
my daughter will make the choice
for herself. she's seven now.
when she can pronounce humanpapillomavirus and know the meaning of it, i'll let her decide what's best for her.
she's suffered hand, foot and mouth disease; roseola; severe eczema; strange rashes; all after immunizations. doctors said nah, that's not a side effect. did i mention she was born with vitiligo? doctors said nah, don't see it. hmmmmm, my son developed diabetes type one after an immunization. the thing is we have no paternal or maternal family history of autoimmune disease. but doctors say we are probably not informed of our families medical histories or we missed something along the way. \

gardasil, untested.
my daughter, not a guinea pig. and still a virgin. thank you

At 2:42 PM, Anonymous Anonymous said...

As a parent of two autistic children, I have serious concerns about vaccines. On the other hand, as someone with several autoimmune problems and repeated bouts of cervical cancer from HPV, I am seriously considering the HPV vaccine for my daughter.

1. A few thoughts here - the HPV vaccine is NON-INFECTIOUS - in other words, its not a live virus that can cause infection like the flu virus for instance. So as long as it is not manufactured with mercury (hopefully we have stopped that in all cases, not just kids vaccines), its a relatively low risk vaccine.

2. HPV is NOT just a disease of the permiscuous - the age recoomendation makes sense for a number of reasons. First, I think most moms like to believe their tweens and young teens are virgins, yet studies indicate a great number of them are participating in some sort of sexual activity, if not intercourse. Its niave to think you are exempt from ignorance of your child's activities. Not to mention the fact that many young girls are molested every day by family members, teachers, and other caretakers that we obviously never thought capable of such things. Finally, it doesn't take actual intercourse to transmit; mere skin to skin contact, including even rarely oral sex, can transmit the virus.

3. Autoimmune diseases are complex puzzles of diseases and usually have their origins in a number of different factors, including not only genetics, but nutrition, environmental exposure, exposure to antibiotics, mercury, and yes live vaccines, as well as other factors we probably don't even know about yet. To assume that only one factor is the CAUSE of any particular childs immune problems is misguided. While I support a healthy skepticism about vaccines, and most of mainstream pharmaceutical intervention, being immune-compromised makes a young girl or woman that much more vulnerable not only to "catching" HPV, but never being able to fight it off and developing cervical dyplasia and cancer as a result.

4. Although cervical cancer is often highly treatable, the treatment often compromises fertility even when the disease is caught early. Moreover, given the great inaccuracy of pap smears in this countries, I personally don't feel terribly comforted even by regular screening. I recently lost a young (under 50) friend to invasive cervical cancer. She was a doctor who never missed a pap, yet when they found it, it has already spread to several major organs. So please consider the real and sometimes life-threatening consequences of HPV in your decision about vaccines.

Just my two cents... Glad people are talking about this stuff.


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