Chicken Pox

My son is 2 years old and has been in contact with a child who has chicken pox . He as not received chickenpox vaccine so far. Can I give him chicken pox vaccine now for his protection ?
Answer: chicken pox vaccine is highly effective ( 95% for the prevention for moderate to severe disease) when used within 36 hours of exposure in an environment involving close contact . It should be given as soon as possible after the exposure but is recommended up-to 5 days after exposure. The reason for high efficiency is that naturally acquired varicella-zoster virus usually takes 5-7 days to propagate in the respiratory tract before primary viremia and dissemination occur , where as vaccine virus may elicit humeral and cellular immunity in significantly less time.
Question: Is MMR vaccine effective in preventing measles if given after exposure to the illness?
Answer: The measles vaccine if given within 72 hours of measles exposure will provide protection in some cases , so vaccination within 72 hours is recommended for all unvaccinated contact including children as young as 6 months. In children less than 1 year this vaccine should not count as part of primary service, which should continue as usual ( with the minimum of 28 days of separating vaccines).