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Gardasil effectiveness clarification Dr. Handsfield
Hello,
I'm hoping Dr. Handsfield will reply to this question, as it addresses a question posed by another user concerning Gardasil effectiveness. In the following thread, Dr. Hansfield states that there is "no protection against HPV after the first Gardasil shot." http://www.medhelp.org/posts/STDs/Protected-Sex-w--Genital-Warts-After-1st-Shot-of-Gardasil/show/1704033.
However, the other user mentioned in his question the 97% effectiveness offered by a single dose of Gardasil, which is correct according to this study by Merck: http://www.lifewhile.com/health/5064766/detail.html. Recent data regarding another HPV vaccine, Cervarix, has demonstrated equal HPV protection with fewer than 3 doses, and even comparable efficacy in single doses.
So my question is this: who is right? Dr. Handsfield, or the Merck representative quoting data from a formal study? This isn't meant to sound rude. I'm just honestly trying to understand why Dr. Handsfield (who is an STD expert) disagrees with the study, and why. It is my understanding that upon antigenic exposure, the body initiates antibody production, so I imagine there is no reason why this wouldn't occur following a single dose of Gardasil. One would imagine there would at least be partial protection. And I am confused with the studies concerning antibody titers and HPV immunity. Some studies indicate that even years after Gardasil, despite low antibody titers, patients who received the series are still immune (perhaps due to cellular memory rather than a humoral response). So, in conclusion, who is right, Dr. Handsfield, or the study?
I'm hoping Dr. Handsfield will reply to this question, as it addresses a question posed by another user concerning Gardasil effectiveness. In the following thread, Dr. Hansfield states that there is "no protection against HPV after the first Gardasil shot." http://www.medhelp.org/posts/STDs/Protected-Sex-w--Genital-Warts-After-1st-Shot-of-Gardasil/show/1704033.
However, the other user mentioned in his question the 97% effectiveness offered by a single dose of Gardasil, which is correct according to this study by Merck: http://www.lifewhile.com/health/5064766/detail.html. Recent data regarding another HPV vaccine, Cervarix, has demonstrated equal HPV protection with fewer than 3 doses, and even comparable efficacy in single doses.
So my question is this: who is right? Dr. Handsfield, or the Merck representative quoting data from a formal study? This isn't meant to sound rude. I'm just honestly trying to understand why Dr. Handsfield (who is an STD expert) disagrees with the study, and why. It is my understanding that upon antigenic exposure, the body initiates antibody production, so I imagine there is no reason why this wouldn't occur following a single dose of Gardasil. One would imagine there would at least be partial protection. And I am confused with the studies concerning antibody titers and HPV immunity. Some studies indicate that even years after Gardasil, despite low antibody titers, patients who received the series are still immune (perhaps due to cellular memory rather than a humoral response). So, in conclusion, who is right, Dr. Handsfield, or the study?
MEDICAL PROFESSIONAL
Thanks for the thanks. Glad to have helped.
Thanks for the great information and clarification, Dr. Handsfield! Keep up the great work!
MEDICAL PROFESSIONAL
All the studies with Gardasil (and I suspect for Cervarix as well) did HPV DNA testing as well as cytology at every patient visit. Lots of data have been published on efficacy against HPV per se, in addition to CIN. Some published reports may have presented data on only CIN, but I think most if not all included HPV efficacy itself.
Dr. Handsfield, thank you for your information. It is greatly appreciated. If I might ask a single last question concerning Gardasil,
In these initial trials, were they performing PCR to screen for HPV infection in women after each vaccine dose? I've always wondered this, because in reading some studies, it seems that the researches were only looking for CIN, and not necessarily HPV infection alone. I always was curious if this could skew the efficacy rate of the vaccines, because you can obviously have HPV infection, and no noticeable cervical changes.
In these initial trials, were they performing PCR to screen for HPV infection in women after each vaccine dose? I've always wondered this, because in reading some studies, it seems that the researches were only looking for CIN, and not necessarily HPV infection alone. I always was curious if this could skew the efficacy rate of the vaccines, because you can obviously have HPV infection, and no noticeable cervical changes.
MEDICAL PROFESSIONAL
"You state that it is clear that no protection is awarded from the first dose, but from what I have observed, there are simply no formal clinical trials that directly observe how much protection is awarded from single doses of the vaccine. If there are, where might I find them?"
The data on low efficacy of a single dose have not been published, to my knowledge. However, for 5 years I served on two of Merck's HPV vaccine advisory panels, so I have had the opporunity to see unpublished data. Among the thousands of subjects who received Gardasil in the initial efficacy studies, naturally some failed to return on schedule for the second dose, but when they showed up later were retested for HPV. Some such persons had become infected with the HPV types covered by the vaccine. Probably similar data exist for Cervarix. No vaccine/HPV experts believe single doses provide significant protection.
As for two doses, research has indeed been underway to more accurately determine efficacy, and the link you provide summarizes preliminary analysis of one such study. It may be that 2 doses will prove quite effective. But also note the closing sentence: "More studies are obviously needed in order to adequately determine the effectiveness of fewer doses." Until such results are available and prove consistent in several studies, people should not rely on being well protected against HPV until they have received all 3 doses.
That should end this thread. Take care.
The data on low efficacy of a single dose have not been published, to my knowledge. However, for 5 years I served on two of Merck's HPV vaccine advisory panels, so I have had the opporunity to see unpublished data. Among the thousands of subjects who received Gardasil in the initial efficacy studies, naturally some failed to return on schedule for the second dose, but when they showed up later were retested for HPV. Some such persons had become infected with the HPV types covered by the vaccine. Probably similar data exist for Cervarix. No vaccine/HPV experts believe single doses provide significant protection.
As for two doses, research has indeed been underway to more accurately determine efficacy, and the link you provide summarizes preliminary analysis of one such study. It may be that 2 doses will prove quite effective. But also note the closing sentence: "More studies are obviously needed in order to adequately determine the effectiveness of fewer doses." Until such results are available and prove consistent in several studies, people should not rely on being well protected against HPV until they have received all 3 doses.
That should end this thread. Take care.
http://www.vaccineinjuryhelpcenter.com/fewer-doses-of-cervarix-may-be-just-as-effective-according-to-new-study/
That is another recent article that highlights the data from a study concerning Cervarix, that indicates similar efficacy rates in women only receiving one or two doses of the vaccine. I understand that these are not the formal articles, but most are published within journals in which I do not have access to. I'm honestly just trying to figure this out, and it's confusing. Seemingly more recent studies are in fact indicating efficacy in the "less than standard" 3 dose series.
That is another recent article that highlights the data from a study concerning Cervarix, that indicates similar efficacy rates in women only receiving one or two doses of the vaccine. I understand that these are not the formal articles, but most are published within journals in which I do not have access to. I'm honestly just trying to figure this out, and it's confusing. Seemingly more recent studies are in fact indicating efficacy in the "less than standard" 3 dose series.
Yes, I understand that the article is not a formal study, but it is deriving information from one. Numerous other reports highlight the same information.
For instance: "On average, these women were followed for approximately two years. In this group, GARDASIL reduced the risk of developing high-grade pre-cancer and non-invasive cancer (CIN 2/CIN 3, or AIS) associated with HPV types 16 and 18 by 97 percent (n=5,736); one case was observed in the vaccine group compared to 36 in the placebo group (n=5,766). " This relates to women who did not complete the series, etc.
Dr. Eliav Barr, Merck's head of clinical development for Gardasil, has quoted these numbers, and has stated that the data is more reflective of "real world" practices, as many women don't follow up on the series, etc. So I do not think it is a matter of the reporter simply getting it wrong. And the data was derived directly from the first Merck Gardasil trials.
You state that it is clear that no protection is awarded from the first dose, but from what I have observed, there are simply no formal clinical trials that directly observe how much protection is awarded from single doses of the vaccine. If there are, where might I find them?
I am just having trouble understanding why a single dose would not provide some degree of protection, as the body responds to antigenic stimulation.
For instance: "On average, these women were followed for approximately two years. In this group, GARDASIL reduced the risk of developing high-grade pre-cancer and non-invasive cancer (CIN 2/CIN 3, or AIS) associated with HPV types 16 and 18 by 97 percent (n=5,736); one case was observed in the vaccine group compared to 36 in the placebo group (n=5,766). " This relates to women who did not complete the series, etc.
Dr. Eliav Barr, Merck's head of clinical development for Gardasil, has quoted these numbers, and has stated that the data is more reflective of "real world" practices, as many women don't follow up on the series, etc. So I do not think it is a matter of the reporter simply getting it wrong. And the data was derived directly from the first Merck Gardasil trials.
You state that it is clear that no protection is awarded from the first dose, but from what I have observed, there are simply no formal clinical trials that directly observe how much protection is awarded from single doses of the vaccine. If there are, where might I find them?
I am just having trouble understanding why a single dose would not provide some degree of protection, as the body responds to antigenic stimulation.
MEDICAL PROFESSIONAL
Welcome to the forum.
I looked at the link you provided. I'm afraid it is in error. It's not an actual scientific report but a news story from 7 years ago, even before the first study was published). The reporter got it wrong. I stand by my reply in the earlier thread (and several others in this forum over the past few years). The data are very solid that there is no protection after the first dose of Gardasil (or Cervarix, the GlaxoSmithKline HPV vaccine against HPV 16 and 18) and complete protection after the third dose at 6 months. The amount of protection after only two doses is unclear; it may be somewhat effective, but it shouldn't be relied upon.
It's not as if I'm alone in this opinion. Any basic online search about the HPV vaccines will confirm what I have said. You could start with the information provided by the two manufacturers.
I hope this makes things clear. Best wishes-- HHH, MD
I looked at the link you provided. I'm afraid it is in error. It's not an actual scientific report but a news story from 7 years ago, even before the first study was published). The reporter got it wrong. I stand by my reply in the earlier thread (and several others in this forum over the past few years). The data are very solid that there is no protection after the first dose of Gardasil (or Cervarix, the GlaxoSmithKline HPV vaccine against HPV 16 and 18) and complete protection after the third dose at 6 months. The amount of protection after only two doses is unclear; it may be somewhat effective, but it shouldn't be relied upon.
It's not as if I'm alone in this opinion. Any basic online search about the HPV vaccines will confirm what I have said. You could start with the information provided by the two manufacturers.
I hope this makes things clear. Best wishes-- HHH, MD
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