For Varicella zoster (chicken pox), when are vaccination/antiviral drugs effective?

Question

The UK does not routinely vaccinate its citizens against chickenpox though the info website of the chief healthcare provider acknowledges that vaccinations are available and there are also circumstances where antiviral drugs may be prescribed

I recently received advice from my doctor that there isn't much point in either vaccinating or prescribing drugs for chickenpox, and the consensus for adults who have never had chickenpox seems to basically be that you take your chances, suffer the infection should it be contracted and serious complications are unlikely though it's more unpleasant to contract as an adult than as a child

I'm thus confused as to why the NHS website would create one impression (steps can be taken for adults with no chickenpox immunity) and the doctor another slightly different impression (steps aren't taken..). While there isn't a direct contradiction, neither source has said when steps are taken, but the doctor implied that steps aren't taken because there is no point.

In what context would it make sense for an adult with no immunity to get vaccinated, or to take antiviral drugs?

I presume that vaccination would only be successful up to the point that said adult is exposed - walk into a party and be greeted by a child with full on chickenpox and it's too late for vaccination.. but what about antivirals? Could that adult go home, and start a course of drugs that would effectively kill any viruses they'd contracted, before developing a full blown infection of their own?

What about the situation where said adult lives with a child who wakes up one morning with a chickenpox rash? Given that the child is apparently contagious a few days before the first spot, is the adult likely too far along the infection timeline themselves for antivirals to have any effect? Is there a point of no return, beyond which AV drugs are ineffective, and for chickenpox this point is so early that it's usually too late by the time anyone realises?

Answer 1

According to the World Health Organization

• Administering the vaccine up to 3-5 days after exposure has been shown to reduce the severity of the disease significantly, but studies vary greatly as to whether or not post-exposure vaccination can prevent the disease entirely.
• Post-exposure treatment with antiviral drugs is effective at reducing the severity of the disease, but due to the expense and low expected benefits, it is only recommended for immunocompromised individuals or patients at risk of severe complications.
• Vaccination of adults is less effective than vaccination of children: children frequently get full protection after a single dose, while adults usually require two doses. Additionally, vaccination of children provides protection for upwards of ten years, while immunity in vaccinated adults fades after a few years.