It's estimated that 300 million people have HBV. HBV is currently incurable once acquired, at which point the vaccine is irrelevant.

The HBV virus is also carcinogenic, which makes it unique[0] among the three big hepatitis viruses. Liver cancer is extremely aggressive and fast-killing, often reaching terminal stages before it is even detectable at all. It is one of the top three causes of cancer deaths worldwide.

Aside from the sheer number of people affected by this, it is also a horrible thing to experience. I have watched someone die from liver cancer, and I would not wish it on anyone.

Contrast to HSV, which is widespread (approximately half the population has at least one HSV latent infection) and causes very few problems beyond occasional irritation in virtually all cases that do not involve other comorbidities or immunocompromised status. HSV is also suppressible through antiviral treatment, making it generally untransmittable (if treated and suppressed) and unlikely to cause symptoms. Most people with HSV do not even bother to do this, which is if anything a testament to how little HSV affects their lives (most don't even know they have it, and there is no clinical justification for routine testing in otherwise healthy patients).

Of all infections pathogens for which I could wish a cure into existence, HSV would be extremely low on my list.

[0] While HCV can cause cancer if left untreated for a long time and if it causes cirrhosis, approximately one third of people clear HCV infection in the acute stages without any lasting ill effect. Of the remainder, it takes a long time for cirrhosis to develop, leaving plenty of time for treatment. First-line treatments are approximately 95-99% effective. So there is no clinical reason HCV needs to increase a person's risk for cancer, as long as they have access to medical care. The same is not true for HBV.

https://pubmed.ncbi.nlm.nih.gov/39956964/

Link between HSV and dementia

...HSV would be extremely low on my list.

I think this is a bit of an unfair conclusion.

First, while you're correct that most people who have HSV have few symptoms (if any), you're discounting the fact that, because so many people are infected, there are millions upon millions who have highly-visible and highly-painful infections. Many of these people struggle with relationships and mental health as a result.

Second, HSV is associated with higher risk of HIV infection for obvious reasons.

Finally, discovering effective treatments for such a difficult virus would probably produce insights that have implications for other difficult-to-target viruses.

So I don't think we should dismiss HSV on the basis that it's so common and doesn't cause life-threatening symptoms. Medicine should pay adequate attention to infections that affect quality of life for large numbers of people.

Billions are spent on treatments for super rare diseases, many of which are terminal, and in the best cases the end result is often that pharmaceutical companies have drugs costing tens or hundreds of thousands of dollars that extend life by months (often with dubious quality of life).