HPV Vaccine Efficacy

Figure 1 US rates of CIN2+ lesions by age group, adapted from Gargano et al 2019

The Human Papilloma Virus (HPV) vaccine Gardasil/Gardasil 9 has been in the news of late regarding its safety. I’ll touch on the safety issues in a moment but what isn’t emphasized is what an impact this vaccine has already had at preventing HPV infections, lesions and cervical cancer.

Gardasil was first launched in the US in June 2006 as a tetravalent HPV vaccine for use in females aged 6-26. Over time the product has been improved to be active against 9 HPV types, Gardasil 9, and its label has expanded to a encompass use in a wider age range of both females and males.

In 2021 data was published in MMWR showing  the impact Gardasil has had on HPV infections in the US. The report found that there was an 88% reduction in HPV infections in girls aged 14-19 and an 81% reduction in women aged 20-24.

Multiple studies have also reported a reduction in pre-cancerous lesions (Cervical Intraepithelial Neoplasia, CIN2 and CIN3) including Gargano et al 2019 who saw a decline of up to 94% in US women aged 18-20 and up to 62% in US women aged 21-24 (see Figure 1).

Finally, to return to the issue of safety, neither the CDC or EMEA found the vaccine to have any major safety issues. Of course, that doesn’t mean to say that some individuals may have some form of an adverse reaction. By their very nature vaccines stimulate an immune response which may be more excessive in some individuals than others. Guillain-Barré syndrome (GBS) is probably the best-known example where individuals can develop autoimmune and neurological issues following the administration of influenza vaccine, but those individuals would, and do, have the same reaction if they are infected with influenza virus itself.

It's an ongoing conversation, and new research may continue to influence public health guidelines, but the foundational data so far supports the idea that HPV vaccines are a safe and effective tool in preventing disease.