Look into how HPV prevalence has changed since 2013-2016

[jeffkaufman]

In hpv.py we have an NHANES estimate from a 2013-2016 study, but we're interested in prevalence in 2020 and 2021. HPV prevalence probably decreased since then because vaccination is increasing and they're covering more subtypes (per @simonleandergrimm), so extrapolating to 2020 and 2021 without adjusting for this might not be very good.

[jeffkaufman]

Currently I've left the incidence estimate in, because the paper has:

we assumed prevalence of infection was comparable in 2013–2016 and 2018. In the 8–10 years following vaccine introduction in 2006, while vaccine-type HPV prevalence decreased dramatically in younger females, non-vaccine-type HPV prevalence remained stable in most age groups.(19, 20) This suggests there have not been substantial changes in the risk of HPV acquisition during this time period.

Extrapolating 2-3 more years, to 2020-2021, I expect the pandemic to be a larger issue than vaccination

[simonleandergrimm]

Left a comment that explains why we think extrapolation is fine some time ago, closing this issue.

# HPV prevalence (any subtype) was extrapolated in the study from
# 2013-2016 to 2018. We extrapolate forward to 2020 and 2021. Though there
# is a 9-valent vaccine that got rolled out in 2016, this should not have
# a very large effect on prevalence, as only young individuals are
# vaccinated."