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Dear Dr. Roach: I know people who home-school their children rather than let them attend public school because they won’t allow their children to be vaccinated as required by the schools. There must be studies that show the percentage of children who are adversely affected by vaccinations as opposed to those who are adversely affected by actually having the diseases.

Can you discuss this?

M.F.

M.F.: Vaccine requirements differ from state to state for school-age children, but in California, a bill recently was passed mandating vaccines for polio; diphtheria, tetanus, pertussis (DTP); measles, mumps, rubella (MMR); hepatitis B; and varicella (chickenpox). Children who are not fully vaccinated will be unable to attend public school unless they have a medical reason not to be.

Some of these conditions are now quite rare in the U.S. and Canada, so adverse events from vaccine-preventable diseases are rare.

In fact, the United States was declared measles-free in 1990.

However, children and adults still can be exposed to measles, and recent outbreaks show that transmission still can occur, probably from a visitor from a country that still has measles, especially as immunization rates in the U.S. have decreased in certain communities. There have been about 800 cases of measles in the U.S. in 2014 and 2015 so far, with one death.

These vaccines are very, very safe. While minor side effects occur occasionally, serious side effects occur very rarely. For the MMR vaccine, the rate of a serious reaction, such as severe allergic reaction, are less than 1 per million.

Autism, once incorrectly claimed to be triggered by the MMR vaccine, has been shown in many studies to have no association with the vaccine.

The vaccination rate is still very high, and for this reason measles has not spread widely in the U.S. Until measles is eradicated from the world the way smallpox was, measles vaccination still is required to prevent a devastating outbreak, since measles is remarkably contagious. The arguments are identical for polio, diphtheria, rubella and mumps. Varicella is still endemic, and a vaccine helps protect against serious complications.

Being totally compliant with recommended vaccines is very (but not 100 percent) safe, it protects you and your children, and it protects people with immune system disease who cannot protect themselves with vaccines.

Dear Dr. Roach: I was put on Coumadin several years ago for atrial fibrillation. It was a perpetual pain in the butt, all those tests and never knowing from day to day how much the blood had been changed from meal to meal. Both extremes were dangerous. I had two friends on Coumadin who were in remote areas when they fell, both hitting their head. Both died from brain hemorrhage before they could be treated at a hospital. My doctor suggested Pradaxa, a more expensive product, but no testing required. From what I read, there is no more danger of internal bleeding from one than from the other, and apparently Coumadin can be reversed medically in an emergency room while Pradaxa cannot (true or false?).

It would be helpful for you to explain the chemical/medical differences between the two drugs; how they work and why they work differently; and an opinion as to which is the safer to use, and why.

C.L.

Dear C.L.: Atrial fibrillation, the chaotic beating of the top part of the heart, puts people at higher risk for blood clots, and is one of the most common reasons to prescribe warfarin (Coumadin). Warfarin really did start off as rat poison, but, like many drugs, its useful as a medicine in small doses even if it is potentially deadly in high doses. It has been in use for 60 years. Unfortunately, it is ineffective if you don’t give enough and can cause serious bleeding if too much is given, as happened to your friends. The INR blood test (international normalized ratio) is used to determine the correct dose, and the usual desired range is 2-3, although people with mechanical heart valves need a slightly higher dose, 2.5-3.5. Blood testing needs to be done at least every few weeks, and much more often when just starting and in people whose levels go up and down. Since warfarin works by blocking vitamin K, people on warfarin need to have a consistent vitamin K intake, which is mostly found in green, leafy vegetables. Vitamin K will reverse the effects of warfarin in half a day or so, but blood products can be used to immediately reverse the effect.

Dabigatran (Pradaxa) is a new medication that works by directly blocking thrombin, a key protein in making clots. Dabigatran should not be given to people with poor kidney function or disease of heart valves. There is no way to reverse its effects.

Studies comparing warfarin and dabigatran have shown similar rates of effectiveness and a slightly lower risk of brain hemorrhage with dabigatran. Some studies show a slightly higher risk of heart attack in people taking dabigatran.

In my opinion, both are reasonable choices. Pradaxa may be more convenient since it doesn’t require testing and appears to be about as effective, and with a lower risk of brain hemorrhage. However, there is no antidote, and it needs to be taken twice daily.

Email questions to ToYourGoodHealth@med.cornell.edu.

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