DEAR DR. ROACH: Three years ago, I turned 60 and received my first dose of Shingrix. I had a highly unpleasant reaction, with fever and flulike symptoms. I did not return for the second dose until last week, so although I have had two doses, they are three years apart. Do I need to get another dose in a short window of my most recent vaccination or will I be considered protected since I have had two doses, just significantly spaced apart? By the way, no reaction this round other than a sore arm! – K.B.S.

ANSWER: The new two-dose shingles subunit vaccine (Shingrix) is a highly effective treatment to prevent shingles and its complications. It is recommended you get the second dose two to six months after the first dose. According to the Centers for Disease Control and Prevention:

“The vaccine series need not be restarted if more than 6 months have elapsed since the first dose; however, the efficacy of alternative dosing regimens has not been evaluated, data regarding the safety of alternative regimens are limited, and individuals might remain at risk for herpes zoster during a longer than recommended interval between doses 1 and 2.”

Despite that somewhat reassuring statement, three years seems to be pushing it to me, and I would really consider getting a third dose two to six months after the dose you just took. You may (or may not) get a reaction, but you would be surer about having protection against shingles.

DEAR DR. ROACH: I had my thyroid removed in 2004 due to papillary carcinoma. I see an ear, nose and throat doctor once a year, at which time I have an ultrasound of my neck area. My primary care physician orders blood tests every three months to primarily determine if my levothyroxine dosage is correct. Please advise which thyroid-related blood tests that you would recommend to appropriately monitor my level of medication. My ENT told me that an incorrect dosage may result in heart issues. – J.E.

ANSWER: Measuring the thyroid hormone itself, levothyroxine, and thyroid stimulating hormone, made in the pituitary, are adequate to monitor the thyroid level in most people. There is a fairly broad range of these hormones, but when both are in the normal range, that’s usually a good place to be. If the thyroxine level is low, the body responds by increasing the TSH level. If thyroxine is high, the TSH level goes way down. It’s when thyroxine is high that the heart can be damaged, particularly by the development of atrial fibrillation.

In most people with a history of thyroid cancer, experts recommend a thyroxine level just on the high side of normal. That means the TSH level will be low-normal, which is desired because some cancer cells can be stimulated by high levels of TSH. In patients with a higher risk of cancer recurrence, the TSH level may need to be suppressed even below the lower limit of normal. Frequent checks of the thyroid are appropriate to be sure your thyroid levels are not so high that you are at increased risk for developing the heart problems of excess thyroid levels. Other health issues also may occur, such as bone loss. It’s a delicate balancing act between reducing cancer recurrence risk but not damaging the rest of the body.

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.