What if the HPV vaccine only lasts for 10 years?

Once of the concerns tossed around by critics of the HPV vaccine is the fear that it might only delay HPV infections. This was brought up by Dr. Harper on the infamous Katie Couric HPV episode, it’s also not an infrequent comment left on my blog, and of course it’s bandied about by a variety of anti-Gardasil campaigners.

Well, this is what science has to say about it.

First of all, the HPV vaccines are showing good immunity (i.e. they are working well ) at 8-9 years out with no signs of waning effect. It is unlikely that all of a sudden at year 10 there will be a steep decline in protection, so the 10 year HPV vaccine cliff of doom seems unlikely.

Researchers are also monitoring the vaccine for effect over time. It’s not like it is designed, sent out to the general population, and then 20 years out we look back, scratch our heads and say, “Now what exactly happened?” Populations who received the vaccine are followed and if there is a potential sign of reduced effect (drop in antibody levels) then it could be possible a booster dose might be needed. It’s true we won’t know that for 5 or 10 more years or even longer. However, boosters are needed for a variety of vaccines. For example, pregnant women need the pertussis vaccine each time they are pregnant. The potential that a booster might be needed in 10 or 15 or 20 years doesn’t mean a vaccine is bad, it just means a booster is needed. Immunity might not last for ever, that is of course why it is being studied.

It is also important to remember when women get HPV – typically under the age of 24. After high school 26% of young women are HPV positive and three years later another 43% catch the infection (this is a study of both high risk and lower risk virus types).  In this study of college students over 24 months 11% of women tested positive for one of the two very high risk viruses (HPV 16 or 18). Peak HPV time is late teens and early twenties.

We also know how long it takes from HPV infection to progress to pre-cancer and then cancer (graph from Schiffman and Solomon, NEJM 2013 369:24).

So a vaccine given in the pre-teen early teen years that is going to last at least 10 years (and likely longer) is going to cover that peak time of HPV exposure.

So right now we have a vaccine that will prevent HPV infection at the time when women are likely to get it. This is just like the meningococcal vaccine (one of the risk factors for the infection is living in a dorm). It is not a bad thing to have a vaccine that covers you when you  are at the highest risk of getting an infection.

But let’s say (for argument’s sake) that the vaccine only lasts for 10 years

AND no one ever figures out the vaccine only lasts for 10 years

AND no one develops a booster shot

AND these previously HPV immune women who were protected from HPV in their early twenties are now at risk of getting HPV because they are still having sex in their thirties.

In this scientifically improbable scenario (not the sex after college part, but everything else), yes it is possible that HPV acquisition could be delayed. But then that would mean that the risks inherent with HPV infection…the worry, the monitoring, the bits of your cervix being hacked off for diagnosis and treatment etc would also be delayed too, and for many women this would push them past their childbearing.

So the very worst scenario is that women would still get HPV, but they would get it later when it is less likely to have any impact on their reproductive function. The high-grade lesions (the blue HSIL in the chart above) would be happening a decade or more later. That’s bad how?

And again, that last scenario is really unlikely given the vaccine is being followed for effect. And researchers know about booster shots.

So what if the HPV vaccine only lasts for 10 years?

1) Unlikely

2) If it starts to lose effect over time a booster might be needed (no big deal)

3) Delaying diagnostics and treatments for pre cancer and cancer (interventions that can affect reproductive function) past the child-bearing years would not be a bad thing