Last month the Post-licensure safety study for Gardasil (the HPV vaccine) was released. The study focused on the reports of adverse events as reported to the VAERS database by the manufacturer, doctors and patients or caregivers. Much has been made by detractors of the vaccine about the serious alleged side effects that have struck young women given the course of injections. These allegations have been supported by referring to the VAERS database itself so if they are valid they should be upheld by this study.

Of the 12,424 reports that VAERS received in the 2.5 year period following implementation of the vaccine, 772 (6.2%) were classified as “serious”, the total number of vaccine doses distributed in this period was 23 million. The category of “serious” was defined according to the FDA regulatory definition of an adverse event that “is life threatening; results in death, permanent disability, congenital anomaly, hospitalization, or prolonged hospitalization; or necessitates medical or surgical intervention to preclude one of these outcomes”.

It must be noted at this point that the VAERS database cannot determine causality, the events reported merely have to occur after vaccination takes place. Therefore anything that happens to a patient in this time frame that someone thinks might be related to the vaccine may be entered. I point this out only to remind that while we may be looking at vaccine safety life does go on, accidents happen and co-incidences occur. The point of a study such as this is to determine if these events are occuring at a frequency higher than what we would expect in the normal population. In other words, is there really a correlation between these events and the vaccine or is is simply a statistical fluke.

The study looked into each type of adverse report in detail and attempted to answer the above question, does the rate of reporting exceed that which would be expected in the general population? In almost all cases the answer appears to be “No”, the exceptions to this were reports of syncope (fainting) and venous thromboembolic events (blood clots), this finding will certainly be followed up in future studies. Curiously one of he more prominent adverse effects that has been concerning many on both sides of the debate, Guillain-Barre´ Syndrome was not found to occur more than expected.

Guillain-Barre´ Syndrome is an auto-immune condition that can be brought on by vaccines but also by normal infections. The syndrome is caused when the immune system is stimulated by an antigen but then starts to target the body’s own nervous system, it usually exhibits as an ascending paralysis noted by weakness in the legs that spreads to the upper limbs and the face along with complete loss of deep tendon reflexes. As vaccines are made to induce an immune reaction the link between vaccines and the syndrome is biologically plausible and not controversial in the medical community.

The study concludes favourably but cautiously, as scientific studies are wont to do:

Vaccination with qHPV has the potential to decrease the global morbidity and
mortality of HPV-associated diseases, including cervical cancer. After hepatitis B vaccine, which can prevent liver cancer, qHPV is only the second vaccine licensed with an indication to prevent cancer. The postlicensure safety profile presented here is broadly consistent with safety data from prelicensure trials. Because VAERS data must be interpreted cautiously and cannot generally be used to infer causal associations between vaccines and AEFIs, postlicensure monitoring will continue, and identified signals may be
evaluated using epidemiologic observational studies.

The full study can be found here, a summary of the study here and a comprehensive discussion of the study here.