I think it’s great that we use antiviral therapy to reduce the risk of transmission for women with a high viral load, since post-exposure prophylaxis (vaccine alone, or vaccine + HBIG) can sometimes fail under these conditions. It kind of feels like we should be starting sooner than 28 weeks of pregnancy though. If the baby is born prematurely, there won’t be much time before delivery for the antivirals to start to reduce viral load. It can also be difficult to predict which babies will be born prematurely. Sure, there are some indications, such as twins/triplets, or people who have a history of preterm birth, but these are not guarantees.
In my opinion, there’s also a difference between someone who has a viral load of 500,000 vs 500 million. Treatment would be indicated for both, but the person with 500 million would need treatment for a lot longer to bring the viral load to “acceptable” levels.
Additionally, in some resource-limited countries, HBIG is not routinely available, and even HBV DNA tests can be prohibitively expensive, and only the basic screening test is available. Without HBIG, it feels like achieving a low viral load is even more important. Shouldn’t we prescribe antivirals to all HBsAg+ mothers in such situations? I also understand that antivirals may be expensive, but they are likely more accessible than HBIG, thanks to HIV treatment/prevention programs, which are generally more established and better funded than HBV treatment/prevention programs. For what it’s worth, if I was in that situation and couldn’t get Viread, I’d accept Truvada as an alternative in a heartbeat.
I guess I can’t really think of a downside of starting treatment earlier (e.g. 20 weeks), but it seems like there are some pretty clear downsides to waiting.