If there was close contact, if the 90% rate is accurate, and if occurrence is independent in related individuals, then you would expect 0.10 * 0.10 = 1% of contacts with 2 potentially vulnerable people to result in neither person infected.
1% sounds rare, but rare events happen all the time, and 1% isn't even particularly rare. If you know 100 families, you'...
To add to @BryanKrause's answer re: rare events happen all the time, the children are not out of the woods yet. The mean incubation time for a primary VZV infection (the clinical syndrome known as chicken pox) is 14 days, but often lasts up to 21 days (see Murray Medical Microbiology, Ch. 53). The father is infectious while shedding virus, usually via the ...
Apart from not getting infected due to pure chance (as mentioned already) there is one highly probable explanation (explanation, not overall chance).
People get, but don't show it:
Asymptomatic infection is unusual, but some cases are so mild, they go unrecognised. The primary viraemic phase is followed by a secondary viraemia to the ...
Yes, you can contract it, but it is very unlikely.
The chickenpox vaccine is a live (attenuated) vaccine, meaning that it was weakened.
People who get chickenpox vaccines can spread the vaccine-strain varicella-zoster-virus to others. However, this happens very rarely.
In a 10 year study of Varivax (the Merck vaccine), this happened in ...
An earlier warning regarding medications in children with chicken pox came to the following conclusion:
The safety of ibuprofen suspension in children. (2003)
The risk of invasive Group A streptococcal infection was associated with demographic and environmental factors and persistent high fever. There was no association with the use of ibuprofen or ...
Humans are the only known animal that the disease affects naturally. However, chickenpox has been caused in other primates, including chimpanzees and gorillas.
The varicella zoster virus cannot infect dogs.
My recollection of that time was not that doctors recommended being exposed to chickenpox but rather that parents sometimes chose to expose their children at a time they felt might be more convenient for the family, since everyone would catch it eventually. Some recommended times to get it: while you only had one child to look after (subsequent children then ...
You can continue to work as long as you take the usual common-sense precautions: wear clean clothes and wash your hands.
While varicella is one of the most contagious viruses we know of, the primary route of spread is droplets expressed when an infected person coughs or sneezes. It can also be spread by touching virus from varicella lesions. The virus is ...
It is true that infants receive antibodies from the mother via the placenta in the final trimester of pregnancy and also in breastmilk.
This is passive immunity, because the antibodies (usually IgA type) are passed on pre-formed. They can resist infection but do not form lasting immunity, which requires the body to encounter the infectious ...
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 only way to know the the level of conversion is through bloodwork to measure it and even that can be problematic. From the CD site:
Laboratory evidence of immunity or laboratory confirmation of disease
Commercial assays can be used to assess disease-induced immunity, but they lack sensitivity to always detect vaccine-induced immunity
From the CDC report:
The period of communicability extends from 1 to 2 days
before the onset of rash until lesions have formed crusts.
Vaccinated persons with varicella may develop lesions that
do not crust (macules and papules only). Isolation guidance
for these persons is to exclude until no new lesions appear
within a 24-...