One Shot, Two Shot: Study Finds One Dose of HPV Vaccine Could Be Enough

A teenager bares her band-aid after getting the HPV vaccine.

A teenager bares her band-aid after getting the HPV vaccine.

You’ve heard about the importance of getting an HPV vaccine and the surprisingly low percentage of young women who do so in the U.S.  For various reasons — accessibility, cost, bad information — many who start the 3-part vaccination series do not complete it.

But what if a single dose could protect women from HPV around the globe? The results of a new study suggest it very well could. Researchers found HPV antibodies in the blood of Costa Rican women who had received one dose of an HPV vaccine four years prior, indicating that one shot might be enough to equip the immune system to recognize and fight HPV infection. While antibody levels were higher in women who had received two doses compared to just one, antibody levels were similar between two- and three-dose recipients.

Public health officials have made the case that getting all 3 doses of the HPV vaccine is necessary for full protection.  And they’re not eating their words yet: the vaccine used in the recent study, Cervarix, only guards against two strains of HPV. It remains untested whether Gardasil, which protects against two additional strains of HPV and is the predominant HPV vaccine in the U.S., is effective after a single dose. That being said, the study’s findings are promising for the global fight against HPV.

Take a look at the news release from the American Association for Cancer Research website:

Women vaccinated with one dose of a human papillomavirus (HPV) vaccine had antibodies against the viruses that remained stable in their blood for four years, suggesting that a single dose of vaccine may be sufficient to generate long-term immune responses and protection against new HPV infections, and ultimately cervical cancer, according to a study published in Cancer Prevention Research, a journal of the American Association for Cancer Research.

“The latest Morbidity and Mortality Weekly Report from the Centers for Disease Control and Prevention on vaccination coverage indicates that in 2012, only 53.8 percent of girls between 13 and 17 years old initiated HPV vaccination, and only 33.4 percent of them received all three doses,” said Mahboobeh Safaeian, Ph.D., an investigator in the Division of Cancer Epidemiology and Genetics at the National Cancer Institute (NCI) in Bethesda, Md.

“We wanted to evaluate whether two doses, or even one dose, of the HPV 16/18 L1 VLP vaccine [Cervarix] could induce a robust and sustainable response by the immune system,” she added. “We found that both HPV 16 and HPV 18 antibody levels in women who received one dose remained stable four years after vaccination. Our findings challenge previous dogma that protein subunit vaccines require multiple doses to generate long-lived responses.”

Data for this study are from the NCI-funded phase III clinical trial to test the efficacy of Cervarix in women from Costa Rica. About 20 percent of the women in the study received fewer than three doses of the vaccine, not by design.

The researchers looked for the presence of an immune response to the vaccine (measured by antibody levels) in blood samples drawn from 78, 192, and 120 women who received one, two, and three doses of the vaccine, respectively, and compared the results with data from 113 women who did not receive vaccination but had antibodies against the viruses in their blood because they were infected with HPV in the past.

They found that 100 percent of the women in all three groups had antibodies against HPV 16 and 18 in their blood for up to four years. Antibody levels were comparable for women receiving two doses six months apart and those receiving the full three doses.

The researchers also found that while antibody levels among women who received one dose were lower than among those who received the full three doses, the levels appeared stable, suggesting that these are lasting responses. In addition, the levels of antibodies in women from the one- and two-dose groups were five to 24 times higher than the levels of antibodies in women who did not receive vaccination, but had prior HPV infection.

“Our findings suggest promise for simplified vaccine administration schedules that might be cheaper, simpler, and more likely to be implemented around the world,” said Safaeian. “Vaccination with two doses, or even one dose, could simplify the logistics and reduce the cost of vaccination, which could be especially important in the developing world, where more than 85 percent of cervical cancers occur, and where cervical cancer is one of the most common causes of cancer-related deaths.”

In some parts of the world, including Chile and British Columbia, two doses of HPV vaccine is now the recommended vaccination program, according to Safaeian. But for a single HPV dose, “while our findings are quite intriguing and show promise, additional data are needed before policy guidelines can be changed,” she clarified. “For instance, it is important to note that persistence of antibody responses after a single dose has not been evaluated for Gardasil, the quadrivalent HPV vaccine that is more widely used in the United States and many other countries.”


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  • Lawrence

    I guess, listening to the actual developer of this drug can be illuminating. READ what she says:

    She says that the vaccines are just as dangerous, if not more
    so, than the disease they are meant to prevent, all while thousands of
    children as young as 9 are being given the vaccine, sometimes without
    parental consent. Dr. Diane Harper was a key developer of the Gardasil HPV vaccine.
    Beginning in 2009 she voiced several concerns about the vaccine and its counterpart Cervarix, saying they caused more harm than good.
    In an article published by CBS News, Dr. Harper says, “The rate of
    serious adverse events (from Gardasil) is on par with the death rate of
    cervical cancer

  • Lawrence

    Oh, here we go again trying to push these potentially dangerous drugs on the public so the drug companies can make billions more.

    Didn’t we learn of this corruption in the lost presidential bid when it was discovered that Rick Perry ( R ) of Texas took campaign money from Merck who in turn passed an executive order in 2007 that mandated ( forced) teenage girls in TX to get the vaccine.

    And that Merck stopped at nothing, including hundreds of thousands of dollars at politicians to push these drugs?

    And now WBUR is also promoting these without also reporting the other side of the story? Where is the real information? Where is authentic journalism? Why are there so many pro-drug articles yet no stories about the greedy ways the drug companies push these drugs on people, needed or not?

    And wasn’t it just a few months ago that they did a story that said death could result if we didn’t get a shingles vaccine? and just a few weeks ago that we all needed the flu shot?

    • Robert Miles

      While I am no fan of corporate profiteering, what you are saying medically flies right in the face of known, established facts, “Lawrence,” which I suspect you know, and therefore I hope someone someday puts a well-earned fist deep in your deserving face. I hope it’s very well-muscled individual, perhaps one with a daughter or female loved one of their own.

      • Lawrence

        Well Robert, the facts I listed about the corruption are well established.

        I think the way you confront someone unveiling the facts is interesting, with violence, as if you have no information of your own to articulate.

        Secondly, I feel that if you became informed and read more instead of becoming victim to the propaganda you may look at this issue with an open mind.

        The facts listed are just that. Facts. Rick Perry; the money to politicians are all well known facts. Even the developer of the vaccine herself, Dr. Diane Harper is opposed to it’s dangerous side effects and dubious benefits. This was published by CBS news. Fact.

        I did not see you dispute these facts, I only read that you hope someone will put a fist in my mouth, to shut me up. I wouldn’t mind that comment if you actually had anything scientific to say, or had some compelling arguement, but you don’t.

        I do. As a matter of fact this Newsweek interview with none other than Ray Moyniham who has this to say about the company that sells the HPV vaccine:

        NEWSWEEK: You write that drug makers now aggressively target the healthy. Why?
        Ray Moynihan: The book opens with a quote from a former Merck
        CEO that it was a shame he wasn’t able to make Merck more like the chewing-gum maker, Wrigleys, because then he’d be able to “sell to everyone.”