Gardasil’s safety and effectiveness-Part 47. Long-Term Study

hpv-factsThis is my 47th article on the HPV quadrivalent vaccine, also known as Gardasil (or Silgard in Europe), which can prevent infection by human papillomavirus, substantially reducing the risk of several types of cancers.* Forty-seven** articles about Gardasil and the HPV vaccine! You’d think I would be tiring of it by now, but I think that Gardasil (or Silgard) are critically important in easily stopping cancers.

I find it ironic that people are always looking for the next “cancer cure”, but here’s Gardasil which prevents cancer from even starting. Which people seem to ignore for their children, even if, as parents, they vaccinate their children for everything else.

I tend to focus on Gardasil because there is a general understanding that the uptake of Gardasil amongst the target group (young boys and girls) is falling far short of goals. A recent report from the CDC showed that only 57% of girls and 35% of boys, aged 13-17 years, have received at least one of the three recommended doses of the HPV vaccine. Let’s look at it another way–43% of girls and 65% of boys are being put at risk to contracting some very nasty cancers. According to the CDC, roughly 79 million Americans are infected with HPV–approximately 14 million Americans contract HPV every year. Many individuals don’t even know they have the infection until the onset of cancer.

First, let me provide a bit of background on the disease. Genital human papillomavirus (HPV) is the most common sexually transmitted infection (STI) in the USA. There are more than 40 HPV sub-types that can infect the genital areas of males and females. These same HPV types can also infect the mouth, anus and throat. They are transmitted from personal contact during vaginal, anal or oral sex.

Some HPV subtypes, such as HPV-6 and HPV-11, can cause warts around the genitals or anus, but have low (but not 0) risk of causing cancers. However, the higher risk subtypes, such as HPV 16 and 18, not only cause approximately 70% of cervical cancers, but they cause most HPV-induced anal (95% linked to HPV), vulvar (50% linked), vaginal (65% linked), oropharyngeal (60% linked) and penile (35% linked) cancers. HPV is estimated to be the cause of nearly 5% of all new cancers across the world.

Currently in the United States, the Advisory Committee on Immunization Practices (ACIP) recommends that preteen girls and boys aged 11 or 12 are vaccinated against HPV. The immunization is also recommended for teenage girls and young women up to the age of 26 who did not receive it when they were younger, and teenage boys and young men up to the age of 21.


One of the concerns (usually promoted by antivaccine groups, but usually dismissed by real researchers with real experience with vaccines) is that it is unknown whether the immunization’s effects last longer than a few years. Because Gardasil was only approved in 2006 (although there are, of course, patients who received it during clinical trials during the prior years), data can only be assessed for the past few years, unlike other vaccines that have been available for decades. Thus, we can expect that nearly every year, new data will be published to provide evidence that the vaccination’s effectiveness lasts one additional year.

And a recent study, published in Pediatrics, provides evidence that the effectiveness, measured by the immunity provided by the HPV vaccine, lasted at least 8 years.  The study followed 1781 children, ages 9-15, for 8 years following vaccination with the HPV quadrivalent vaccine (about ⅔ of the group) or a placebo (about ⅓). At month 30, the placebo group received the vaccine.***

The researchers determined the effectiveness of the vaccine by testing the participants’ blood for anti-HPV seropositivity (that is, indication of antibodies to HPV in the blood). The results of the study provide more powerful evidence of the effectiveness of the vaccine:

  • Vaccination-induced anti-HPV response was clinically detectable through month 96 (or 8 years).
  • Among the 429 children who received the vaccine at an average age of 12, none developed any of the four subtypes of HPV disease or persistent infection of ≥12 months’ duration.
  • Acquisition of new sexual partners (among those ≥16 years) was ~1 per year, further indication that the HPV vaccine did not encourage increased sexual activity.
  • The patients who received the placebo, but subsequently at 30 months received the regular HPV vaccine,  had a similar baseline rate of seropositivity to all of the 4 HPV types as those vaccinated at day 1.
  • No new significant serious adverse events were observed for 8 years postvaccination in both genders.

The study authors concluded that:

The HPV4 vaccine administered to preadolescents and adolescents demonstrated durability in clinically effective protection and sustained antibody titers over 8 years. No new significant serious adverse events were observed for 8 years after vaccination in both genders. These long-term follow-up data, along with other extensive postapproval safety surveillance data, should help to encourage practitioners and reinforce national recommendations for HPV vaccination of all preadolescents and young adolescents.

I don’t know how to say this in a new and different way. Gardasil is safe, researchers are not finding any substantial adverse events in large studies. Gardasil is effect, it prevents HPV infection which can lead to cancer. Gardasil simply saves lives.


*An HPV bivalent vaccine, known as Cervarix, is used in some countries, but only provides protection again two of the subtypes most associated with cervical cancer.

**There’s a whole mythology surrounding the number 47 in the Star Trek canon. My use of it is completely random.

***One of the criticisms made by antivaccine groups about vaccine trials is that they rarely, if ever, contain a placebo group. The reason for this clinical trial design is that it would be unethical to put the placebo group at risk of a deadly disease. Some infectious diseases, like whooping cough, can be spread so easily that the placebo group could get sick (and some die) without the vaccine. In this case, because of the early age of the participants, the risk of contracting HPV in the placebo group is negligible. In addition, the placebo group did eventually receive the vaccine at 30 months, and the results showed that they were equally protected.

Key citations:

The Original Skeptical Raptor
Chief Executive Officer at SkepticalRaptor
Lifetime lover of science, especially biomedical research. Spent years in academics, business development, research, and traveling the world shilling for Big Pharma. I love sports, mostly college basketball and football, hockey, and baseball. I enjoy great food and intelligent conversation. And a delicious morning coffee!
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  • Mike Stevens

    And I thought the magic number was 42…..

  • Dorit Reiss

    The fact that this vaccine, which has the potential to save thousands of lives and as you point out is an anticancer vaccine, is so little used is just painful. The fact that it’s because of unsupported anecdotes doesn’t make it better.

    So many preventable tragedies…

    • The evidence is approaching unassailable. We got real science published in real journals…they got anecdotes.

      I guess the story told on YouTube by some crying parents, who have no evidence that Gardasil did anything to their daughter, outweighs 1700 random and unknown (protected by privacy) individuals who got the vaccine without any problems whatsoever. Frustrating.

      • Dorit Reiss

        I am sorry for the parents who believe it. Some of them have suffered real tragedies. I understand the need to blame.

        The problem is when children are denied protection because of these unfounded stories.

        • voxvot

          The “power” of a statistical test depends upon the sample size. Given the distribution and extent of the vaccine program, a sample of less than 2000 individuals seems vanishingly unlikely to me to have sufficient statistical power to validate definitive safety claims.

          It seems to me that the strategy of the provaxers is simply to dismiss any claim of adverse effects that seem to causally correlate with Gardasil as simply being coincidental. It seem likely that this would also be the strategy employed in dealing with negative results in their study subjects. How many people in the sample reported possible adverse reactions that were simply dismissed as coincidental?

          Gardasil is, beside this, an insane way to tackle ONE of the many dangerous consequences for, mostly, young people of the radical sexualisation of society.

          Gardasil will not protect young people from AIDS, syphilis and gonorrhea. In the absence of a return to the habits of morality and self restraint that contributed to the high functionality of Western European civilization, I’d suggest barrier contraception might be a better option.

          Best advice: don’t have unprotected sex with multiple partners over an extended period of time when you are barely sexually mature and should probably be studying math.

          The provax lunatics would rather ignore the deadly consequences of AIDS than forego the opportunity to pump another billion dollar concoction into the bodies of children. Swarm over death.