A Tale of Co-eds, Condoms, and MMR Vaccination

An 18-year-old woman arrives at college never having received an MMR vaccination as a result of maternal concerns. Now, however, after learning about congenital rubella syndrome (CRS) in a genetics class, she would like to receive the vaccine and comes to your infirmary. She has a boyfriend, but denies being sexually active or pregnant. It has been 4 weeks since her last menstrual period. You give her the VIS sheet and administer an MMR. Two weeks later she sees you again and tells you she did an OTC pregnancy test on her urine and it was positive. You confirm the pregnancy in your office. She admits she was untruthful about her sexual history but didn’t think she could get pregnant since they always used condoms. She asks you what the risks are to the fetus having received this vaccine after she became pregnant, according to her calculations.

You tell her:

A. While the risk is lower with the MMR vaccine as compared with natural infection with rubella, it is still a live vaccine and the baby will be at a slight to moderate risk for CRS.

B. No study has ever shown a case of CRS in a mother who received an MMR vaccine in the first month of pregnancy, and you can guarantee that she won’t have a baby with a birth defect related to the rubella virus.

C. MMR administration to a pregnant woman is a contraindication and it is recommended that providers obtain a pregnancy test before vaccine administration in a woman of childbearing age. You apologize for your oversight and make a mental note to contact your malpractice insurance carrier.

D. There is a theoretical risk of damage to the fetus which is why the vaccine is contraindicated in pregnant women, but more than a thousand women have inadvertently gotten the vaccine while pregnant and no birth defects thought to be due to the MMR vaccine have been seen. Thus, MMR vaccination during a pregnancy is not considered an indication for elective abortion. It is designated by the FDA as Pregnancy category C.

Please click here for answer and discussion.

The correct answer is D. “There is a theoretical risk of damage to the fetus which is why the vaccine is contraindicated in pregnant women, but . . .”

Option B is almost correct; no CRS type malformation was seen in a study of 700 women who had inadvertently received an MMR vaccine within 3 months on either side of conception. So, while the risk of a fetal problem is small at most following fetal exposure to the MMR vaccine, one cannot “guarantee” that there is no risk. For example, if the risk of a malformation following MMR vaccination to a newly pregnant female is 1 in 1000, then statistically one may not see a problem in a study looking at 700 women.

References:

MMRII [package insert]. Whitehouse Station, NJ: Merck & Co, Inc.; 2014