Q My son received the chickenpox vaccine when he was 10 years old. He is 19 now. Does he need a booster shot?
Also, my husband and I are 56 years old and we have had chickenpox. Do we need to be vaccinated for shingles?
A Currently, children without evidence of immunity are recommended to go for two doses of varicella (chickenpox) vaccine.
A second dose of the vaccine is recommended for children, adolescents and adults who have previously received one dose.
The minimum interval between the two doses should be around four and six weeks.
For a chickenpox vaccine called Varivax, the two doses can be taken three months apart if the child is below 12. Those older than 13 can wait between four and eight weeks to take the second vaccine dose.
Varilrix, another chickenpox vaccine, can be taken six weeks apart, regardless of age. But it is also possible to wait more than six weeks to take the second shot.
Your son would not require another vaccine dose if a blood test confirms that he is already immune to chickenpox.
He also does not require further vaccination if he developed the infection after the first vaccine dose. This is called breakthrough disease, which refers to "natural" or "wild-type" chickenpox infection that occurs six weeks or more after vaccination, following close contact with a person in the community who has "wild-type" chickenpox.
In general, you are more likely to have a higher level of protection and a lower risk of breakthrough disease after two doses of vaccine, compared with a single dose.
PAINFUL RASH IN ADULTS
Shingles, also called herpes zoster, is a painful skin rash. It is caused by the varicella-zoster virus, the same virus that causes chickenpox.
Only someone who has had chickenpox (or chickenpox vaccine) can develop shingles. This happens because the varicella-zoster virus can stay dormant in the body and be reactivated many years later.
Shingles is far more common in older people and in people whose immune systems are weakened, either by medication, such as steroids or chemotherapy drugs; or by diseases, such as cancer or the human immunodeficiency virus.
A shingles rash usually appears on one side of the body or face.
The term "zoster" comes from the Greek word for "belt" or "girdle", a reference to the characteristic belt-like appearance of the rash.
The rash usually lasts two to four weeks, develops into blisters, and may be accompanied by fever and sensations of burning pain, tingling, over-sensitivity or numbness.
This type of nerve pain can sometimes be severe and last for a long time - even after the rash is gone.
On rare occasions, patients with shingles can go on to develop pneumonia, vision or hearing problems and brain inflammation.
The shingles vaccine, called Zostavax, was first licensed in the United States in 2006.
The single-dose injection is now available here and is recommended for adults over the age of 50. The vaccine can be up to 70 per cent effective in preventing shingles.
For those who still get shingles after being vaccinated, the vaccine can reduce the severity of the resulting nerve pain.
People with a weakened immune system or a history of allergy to the vaccine or its components, as well as women who are (or might be) pregnant, should not go for the shingles vaccine.
Dr Chan Si Min,head and consultant at the division of paediatric infectious diseases at e National University Hospital (NUH)
Dr Sophia Archuleta,senior consultant at the division of infectious diseases at NUH
This article was first published on June 19, 2014. Get a copy of Mind Your Body, The Straits Times or go to straitstimes.com for more stories.