Comment by stared
4 hours ago
But this misunderstands how HPV works. First, there are many strains. Typical tests for oncogenic variants measure around 30 types. The vaccine I received (Gardasil-9, which I took as a male at age 35) protects against nine specific strains.
Second, the body normally clears HPV naturally after 1-2 years. However, natural infection often does not provide immunity, so reinfection can easily occur (even from the same partner or a different part of your own body).
People often assume that HPV is either a lifetime infection or that recovery guarantees immunity - neither is the case!
Does the vaccine guarantee immunity, by contrast?
Parent is overstating the case. Neither infection nor vaccination provides sterilizing immunity [1], but the general reasons to prefer vaccination are (in order of descending quality of evidence & reasoning):
1) you probably haven't had all N strains yet.
2a) you likely haven't been infected with the ones that cause cancer, because they're relatively rare.
2b) ...that is especially true if you're young and not sexually active.
2) being infected with one strain does not provide sterilizing cross-immunity against the other strains.
3) even if you've been infected with a strain, some of the vaccines have been shown to prevent reinfection and reactivation better than natural infection alone.
4) in general, the vaccination-mediated immunity might last longer or be "stronger" than the natural version, since the vaccines are pretty immunogenic, and the viruses are not.
But for point 4, it's well-known that vaccine efficacy is lower for people who have already seroconverted (cf [1]), so there's clearly some amount of practical immunity provided by infection.
[1] The vaccines are roughly 90% effective for the major cancer-causing strains, but it's not a simple answer, and varies a lot by how you frame the question. See table 2 here: https://pmc.ncbi.nlm.nih.gov/articles/PMC8706722/
Also be sure to see table 4 if you're a man. The data for biological men and women are surprisingly different!
What if you're married? Does it still make sense, if you know you won't ever be sleeping with a new partner?
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It's never a guarantee in practice, the CDC says "More than 98% of recipients develop an antibody response to HPV types included in the respective vaccines 1 month after completing a full vaccination series"