In September 2011, Norwegian immunologist, Charlotte Haug, M.D., Ph.D. raised the issue of potential HPV virus replacement in her opinion paper in the New Scientist titled: “We Need to Talk about HPV Vaccination—Seriously”

There is another serious question that may be answered sooner: what effect will the vaccine have on the other cancer-causing strains of HPV? Nature never leaves a void, so if HPV-16 and HPV-18 are suppressed by an effective vaccine, other strains of the virus will take their place. The question is, will these strains cause cervical cancer?

Dr. Haug noted that vaccinated women showed an increased number of precancerous lesions caused by strains of HPV other than HPV-16 and HPV-18. She also wrote “…the results are not statistically significant, but if the trend is real – and further clinical trials should tell us in a few years – there is reason for serious concern.”

Even in 2009, a voice of concern by medical researchers about virus replacement was raised:

… However, the biological mechanisms of different HPV types are not yet fully understood, and the significance of cross-protection is limited by a small number of lesions, short study period, and lack of data on ICC. It is worth noting that following HPV vaccine implementation, other high-risk HPV types than HPV 16 and 18 could replace the biological niche of HPV 16 and 18, thereby causing a relatively greater proportion of cervical cancer and cervical cancer precursors cases [9,10]. If this occurs, there is a potential to offset the benefits of vaccination. HPV vaccination evaluation programs should consider this possibility and evaluate changes in HPV type distribution in high-grade lesions and ICC over time relative to HPV types found in the general population with documentation of HPV vaccination history. Long-term follow-up during further vaccine evaluation is expected to address those two issues.

Even though the above published papers raise important questions, this study out of the UK titled, “Potential overestimation of HPV vaccine impact due to unmasking of non-vaccine types: quantification using a multi-type mathematical model“, published on May 14, 2012, cites, “There could be an apparent maximum increase of 3-10% in long-term cervical cancer incidence due to non-vaccine HPV types following vaccination”. The authors, from the Health Protection Agency in London conclude that “[u]nmasking may be an important phenomenon in HPV post-vaccination epidemiology, in the same way that has been observed following pneumococcal conjugate vaccination”.