Many wonder whether there’s a benefit to receiving the #HPV #vaccine past a certain age, like 45. Guidelines differ and have changed over time.
The “basic science” remains the same: vaccination will prevent new infections, no matter how old you are. But there have been reasons for an age limit that are important to understand. 1/8
First, HPV does not cause cancer overnight. In those rare instances where infection leads to cancer, it takes years or decades to develop. Vaccination today will prevent cancer, say, 20 years from now. This means more disease is prevented by vaccinating young vs. old (relatively many vs. few years/exposures in their future). 2/8
Second, the HPV vaccine has historically been under-manufactured by Merck, disproportionately going where the company could make the most money on it. Since vaccine was so limited, policymakers worldwide were forced to limit the vaccine to those for whom it would make the biggest difference: young girls. 3/8
Thankfully due to mounting pressure, vaccine manufacturing is up and more equitably distributed. Age limits have expanded. Moreover, years of data show that fewer than 3 doses provides good protection. This means more vaccine to go around, and more bang (medical impact) for each dose. 4/8
Vaccine recommendations have also expanded to include boys. It’s important to recognize that men spread HPV to women (the virus doesn’t spontaneously generate itself in female bodies!). Further, men get HPV-related cancers of their own at the throat, tongue, genitals, etc. 5/8
This is the tension between personal medicine, epidemiology, and policy. Policy tries to do the most good for the most people, informed by the science. But circumstances change, science improves, lifespans lengthen, and each individual is different. 6/8
For example, a healthy, sexually active 46-year-old might prioritize getting the vaccine because they expect new exposures and expect to have many years remaining in which cancer could possibly develop. There is nothing scientifically magical about being 45 vs. 46. 7/8
I know this answer is complicated and multi-faceted, but I hope I’ve provided some insight into the soundness of the basic science, why conflicting guidelines exist, and the tension between the ideal and practically possible in a world of limited wealth and inequitable supply. All views my own. 8/8
@chasewnelson All those threads are just wonderful science educating, thank you.
