I’ve written more than 30 articles about the safety and effectiveness of various versions of the HPV vaccine (also known as Gardasil, Cervarix and Silgard, depending on the region where its sold and the the number of antigens in the vaccine). I’ve also debunked numerous myths and tropes about the long term safety of Gardasil and other HPV vaccines.
There have been huge studies, one that includes over 200,000 patients and another that includes over 1 million patients, that have provided solid and nearly incontrovertible evidence that support the long term safety of Gardasil and other HPV vaccines.
Though it is frustrating that some researchers publish “evidence” from small studies that are poorly designed in an attempt to invent issues with HPV vaccines, if you look at the best designed unbiased studies, the facts are clear–Gardasil is safe and effective. It could be one of the safest and most effective vaccines since it was developed and studied in the era of harsh, and mostly unfounded, criticisms of vaccines by certain antivaccine activists.
All about HPV
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. Additionally, some HPV types can also infect the mouth and throat. HPV is generally transmitted from personal contact during vaginal, anal or oral sex.
HPV is linked to cancers in men and women, and because there are so many subtypes, research has established which HPV types are linked to certain cancers. HPV is believed to cause nearly 5% of all new cancers across the world, making it almost as dangerous with regards to cancer as tobacco. If you are looking for an actual way to prevent cancer, the HPV vaccine is one of the handful evidence-based methods to block some dangerous cancers.
All about HPV vaccines
The original HPV quadrivalent vaccine, known as Gardasil (or Silgard in Europe), can prevent infection by human papillomavirus, substantially reducing the risk of these types of cancers. 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.
A new version of Gardasil, recently cleared by the US Food and Drug Administration, protects teens and young adults from 9 subtypes of HPV, helping prevent even more cancers.
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.
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The long term safety of Gardasil and other HPV vaccines
Despite the vast mountain of evidence supporting the long term safety of Gardasil, it doesn’t hurt to have one more. A new systematic review, recently published in the Pediatric Infectious Disease Journal, which represents one of the largest reviews of clinical trials on the quadrivalent HPV vaccine (Gardasil), found no evidence of any short-term or long-term adverse events. The authors combined data from clinical trials, post-licensing studies, and other data presented at scientific meetings (but, as of this date, not published). The researchers examined adverse events such as autoimmune diseases, neurological disorders, cardiovascular issues, and anaphylaxis.
Simply, the researchers found that none of these serious adverse events were related to the HPV vaccine.
According to one of the co-authors of the study, Dr. Stanley Block, a pediatrician in Kentucky,
This is an incredibly well studied vaccine, with huge data sets and huge populations, and nothing has panned out as being significant as far as major adverse events,. We know the reality is that it protects against a tremendous number of deaths, cancers and chemotherapies for your daughters and your sons somewhat too.
The researchers examined over eight years of data from all types of clinical and epidemiological studies which represented over 2 million doses of the HPV vaccine given to young men and women.
The researchers specifically focused on two active safety surveillance studies in the USA and Denmark. Active studies involve actual examination of medical records of patients who have received the HPV vaccine. This is the best, and most scientific, method to find correlation between a vaccine and a specific adverse event. According to the paper, these two active safety surveillance studies included over 1.6 million doses of the vaccine, and they found that “serious adverse events (AE) were extensively studied and showed no increase in the incidence of these AEs compared with background rates.”
Passive surveillance data
Many people point to the passive data derived from the Vaccine Adverse Event Reporting System (VAERS) to condemn the safety of HPV vaccines. VAERS is considered “passive” because it does not separate temporal events (that is, an event that happens coincidentally after a vaccination) from causal events. VAERS is a system where individuals can report supposed (and sometimes actual) adverse events post-vaccination, to “prove” certain adverse events are related to the vaccination.
The authors stated that first two years of VAERS data following the HPV quadrivalent “vaccine licensure found disproportional reporting venous thromboembolism (VTE).” VTE, which is a conditions where a blood clot breaks loose and travels in the blood, can be serious. However, the possible association of HPV vaccine with VTE was evaluated in the active surveillance studies, mentioned above, and no association was found between vaccination and VTE.
VAERS is one of the favorite “research tools” of the antivaccine crowd, although, if used properly, it can provide “observational data” that can indicate to an epidemiologist a need to establish a hypothesis and determine if controlled data supports or rejects the hypothesis. For example, as recently explained to me by science writer Tara Haelle, observations from VAERS and other passive sources led to the observation that intussusception is associated with rotavirus vaccinations. Although the risk of intussusception is small (especially compared to the various risks of the rotavirus infection itself), parents are asked to be aware of symptoms in case of the rare event. In this case, observational data was used appropriately.
But the problem is that VAERS reports can be made online, by fax or by mail, without medical records that assist in finding potential causal relationships. Passive data needs to be compiled and reviewed before we spend the time to seek out potential causality. Most of the VAERS data cannot be helpful in understanding risks of the HPV vaccine, especially long-term.
VAERS sometimes is used as a feel-good system for those who think that there’s a link between vaccines and something terrible, but without an active investigation, most of the data is not very useful, and it takes a lot of work to find data that might help form a hypothesis about Gardasil safety.
Most epidemiologists know it is probably valueless. Even the VAERS system itself says that the data cannot be used to ascertain the difference between coincidence and true causality. For example, there are tropes across the internet that claim that some number of girls have died from the HPV vaccine, using VAERS data as a “source.” Irrespective of causality, there is, sadly, a background rate for mortality, across all causes, irrespective of whether an individual is vaccinated or not. Unless we understand the background rate of mortality, the vaccine “mortality” rate has no scientific meaning.
What does this all mean, TL;DR
- Huge active surveillance studies have shown that are are no causal links between HPV vaccines and serious adverse events.
- Those same studies rejected the hypotheses, formed by VAERS data, that HPV vaccines were related to venous thromboembolism.
HPV vaccines save lives by preventing cancer. HPV vaccines are safe. Not sure what else I can write.
- Arnheim-Dahlström L, Pasternak B, Svanström H, Sparén P, Hviid A. Autoimmune, neurological, and venous thromboembolic adverse events after immunisation of adolescent girls with quadrivalent human papillomavirus vaccine in Denmark and Sweden: cohort study. BMJ 2013 Oct;347:f5906 doi: 10.1136/bmj.f5906. Impact factor=17.215.
- Klein NP, Hansen J, Chao C, Velicer C, Emery M, Slezak J, Lewis N, Deosaransingh K, Sy L, Ackerson B, Cheetham TC, Liaw KL, Takhar H, Jacobsen SJ. Safety of quadrivalent human papillomavirus vaccine administered routinely to females. Arch Pediatr Adolesc Med. 2012 Dec;166(12):1140-8. doi: 10.1001/archpediatrics.2012.1451. PubMed PMID: 23027469. Impact factor=4.140.
- Vichnin M, Bonanni P, Klein NP, Garland SM, Block SL, Kjaer SK, Sings HL, Perez G, Haupt RM, Saah AJ, Lievano F, Velicer C, Drury R, Kuter BJ. An Overview of Quadrivalent Human Papillomavirus Vaccine Safety – 2006 to 2015. Pediatr Infect Dis J. 2015 Jun 22. [Epub ahead of print] PubMed PMID: 26107345.