DEAR DR. ROACH: If a patient has been fully vaccinated with one of the COVID-19 vaccines within the past three months and subsequently develops symptoms of COVID-19 and tests positive, does this patient need to quarantine/isolate? Why or why not? – C.K.

ANSWER: If a person has COVID-19, they need to be isolated for 10 days after the onset of symptoms. Whether they had the vaccine or not doesn’t matter — they are potentially infectious to others.

No vaccine is perfect, and cases of COVID-19 have popped up in fully-

vaccinated individuals; however, the risk of developing COVID-19 is much lower after vaccination — real-world studies have confirmed a greater than 90% effectiveness for the Pfizer and Moderna vaccines — and their effectiveness at reducing the need for hospitalization or the odds of dying from COVID-19 are even greater.

DEAR DR. ROACH: I’m an 81-year-old male. I have asymptomatic atrial fibrillation. Two trips to the hospital for cardioversions were canceled because I am only in AFib 20% of the time, and both times I was not in AFib. I’m otherwise healthy. If I simply do nothing further, should I be concerned? – W.H.

ANSWER: Atrial fibrillation is a disturbance of the normal heart rhythm. Instead of a reliable beat from the atria (the top chambers of the heart), chaotic electrical activity creates an irregular heart rate.

There are two major problems with having atrial fibrillation. The first is that the heart rate, being irregular, can sometimes get so fast that it causes symptoms or even damage to the heart if it persists. In addition, because of a lack of coordinated electrical activity, the atria do not contract, causing the ventricles to do all the mechanical work of the heart. Most of the time, the heart can handle this, but in people with heart failure or who have damage to the heart valves, this can cause noticeable worsening of heart function.

The second problem is that if the atria don’t contract, the blood can pool and clot, putting a person at risk for embolism. In an embolism, the clot flows downstream, especially to the brain, where it may cause a stroke. Virtually everyone over age 75 with atrial fibrillation, and many people younger who have additional clotting risks, should be on anticoagulant medication to reduce stroke risk.

In addition to anticoagulation, the cardiologist deciding on how to treat atrial fibrillation must choose between controlling the rhythm or the rate. In “rhythm control,” we try to get a person back into normal rhythm; with “rate control,” we allow a person to stay in atrial fibrillation but use medication if necessary to keep the heart rate in a normal range. When a person is in and out of atrial fibrillation, as it seems you are, then electrical cardioversion may not be the right option for rhythm control, and the cardiologist will consider medications, such as flecainide or amiodarone, to keep a person in normal rhythm. Another option is finding and treating the areas in the atria causing the abnormal, chaotic rhythm. This is a process called ablation, which can be done either surgically or, more commonly, with a catheter in the cardiac lab.

The alternative is making sure the heart rate is in a safe range most of the time (including during exercise) by wearing a device to monitor the heart rate and using medication, such as a beta or calcium blocker, to keep the heart rate from getting too high.

I should note that even people who are experiencing atrial fibrillation for a short amount of time are still at higher risk for stroke and need careful consideration of anticoagulation.

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.