DEAR DR. ROACH: You mentioned in a recent column that there is no single-dose measles vaccine. I understand that there are people who object to the MMR combo in the belief that it exposes the child to too many antigens at once. Here is a quote from the cdc.gov website: “Each vaccine in the childhood vaccination schedule has between 1-69 antigens. A child who receives all the recommended vaccines in the 2018 childhood immunization schedule may be exposed to up to 320 antigens through vaccination by the age of 2.”

In fact, a 1994 report from the Institute of Medicine, Adverse Events Associated with Childhood Vaccines, states: “it seems unlikely that the number of separate antigens contained in childhood vaccines … would represent an appreciable added burden on the immune system that would be immunosuppressive.”

I can’t say that the words “seems unlikely” would inspire confidence in those who question the safety of combination vaccines. Is it not possible or feasible to administer single-dose measles vaccines?

— J.D.B.

ANSWER: Too many vaccines at once is indeed a concern for many parents. But there are several reasons why I think the number of antigens in vaccines should not cause a concern.

The first is that a child is exposed to thousands if not millions of antigens daily through exposure to their own bacteria, food and dirt: A child’s immune system is robust enough to handle it.

The second is that the number of antigens in the current vaccine schedule is much lower than it was in the 1960s, as the vaccines now are much “cleaner”: There were 3,217 antigens in the vaccine schedule in the 1960s. Now, there are on the order of 10 times less than the 1960s, and even less than in the single smallpox vaccine kids got 100 years ago.

The third is that by delaying vaccination due to the theoretical concern of overloading the immune system, a child is left unprotected from real diseases, which have potentially severe consequences.

Finally, single vaccines for measles, mumps, or rubella simply are unavailable. The safety data since 1994 continue to show the overall safety of the vaccine schedule, with an extraordinarily low number of serious adverse events, less than 1 in a million.

DEAR DR. ROACH: My wife’s mother and her mother’s father had subarachnoid hemorrhages (SAHs) — he died immediately, and her mother recovered after a time, during which she suffered delusions. Should my wife receive special monitoring? She has always had migraines, which have for the most part been controlled by medicine, but as we get into our older years (70s), I wonder if we should pay more attention to the possibility of an SAH, and what might that entail.

— J.C.

ANSWER: Most subarachnoid hemorrhages, a life-threatening bleed into the head from a ruptured aneurysm, are spontaneous events unrelated to genetics. However, they sometimes come related to a genetic condition, such as Ehlers-Danlos syndrome and polycystic kidney disease. Even when they are not associated with a known condition, people with a strong family history for SAH are at increased risk for one themselves. Someone with one first-degree relative (like your wife’s mother, in her case) has about a 1% chance of having a SAH in the next 10 years. Someone with two first degree relatives has a 7% chance. Your wife would be in between, with one first-degree and one second-degree relative (her grandfather).

There is no consensus on whether she should be screened (with a CT- or MRI-based angiogram scan), but she should discuss it with her doctor, or see an expert, such as a neurosurgeon.

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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.