DEAR DR. ROACH: I am a 60-year-old woman who has been taking a 200-mg tablet of acyclovir (Zovirax) every day for HSV-2 suppression. I may have an outbreak every few years, and they are pretty mild. When I do have an outbreak, I increase my dosage to 1,000 mg per day. What is the procedure when I want to get the shingles vaccine (Shingrix)? Would I need to stop taking the acyclovir for two weeks before getting the vaccine and then be able to continue after? Does taking acyclovir help to suppress shingles in any way? — B.S.

ANSWER: Acyclovir, as well as the related valacyclovir (Valtrex) and famciclovir (Famvir), is an antiviral drug that is used for treatment and sometimes suppression of herpesviruses.

Shingrix is a new, two-dose vaccine for shingles. It is a subunit vaccine, meaning it is made from a viral protein, not from the live virus. You do not need to stop taking the acyclovir before getting the two doses of the vaccine. With the live vaccine (Zostavax), you did need to stop acyclovir, in just the way you suggested.

That’s another advantage of the new vaccine, but the most important advantage is that the new vaccine is much more effective. Disadvantages include its high cost, the need for two doses and a higher incidence of mostly local side effects, such as sore arm, but also fever and just feeling poorly. There is, unfortunately, a shortage in most of the U.S.

Regular doses of acyclovir to chronically suppress herpes outbreaks does reduce the risk of shingles, at least in a high-risk group of people with HIV infection. However, the Shingrix vaccine provides much more potent and, so far, long-lasting protection.

Many physicians would recommend that you try going off the acyclovir to see whether you get recurrences of the HSV-2 (one of the eight strains of human herpes viruses, most commonly causing genital herpes) so often. That part is up to you.

DEAR DR. ROACH: I took a sleep study and slept on my back all night because I was wired up and couldn’t sleep on my side. After a couple of hours, I was told that I have moderate sleep apnea. I snore when I’m on my back, but not when I’m on my side. Do you think I really have sleep apnea? — T.M.

ANSWER: Obstructive sleep apnea very often goes unrecognized. It is caused by the soft tissue in the neck obstructing the airway; the muscles relax while you are asleep, closing the airway. This is indeed much more likely to happen when lying on the back (we use the anatomical term “supine”), and generations of spouses have learned that turning a snorer on the side is a good way to get him or her to quit snoring. Snoring is caused by the very same process that leads to sleep apnea; in fact, snoring is a significant risk factor, with up to a third of snorers having the condition.

I believe the sleep study. While I am sure you would have demonstrated less obstruction if you could sleep on your side, you still are likely to have some obstruction during the night, especially since we frequently change position while sleeping without knowing it. However, there are many different treatments for sleep apnea, and you should talk with your doctor about which is right for you. You need not jump to the most aggressive treatments.

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Dr. Roach regrets that he is unable to answer individual letters, but will incorporate them in the column whenever possible. Readers may email questions to ToYourGoodHealth@med.cornell.edu or send mail to 628 Virginia Dr., Orlando, FL 32803.

Dr. Roach