Can a Vaccine Myth Harbor a Truth?

October 10, 2016

Achilles was a Greek warrior, but did he have a vulnerable heel? Vaccines were once preserved with a type of mercury, but was it linked to autism?

Just as some stories from ancient mythology are thought to contain a kernel of truth, so, too, have elements of popular myths around vaccines been verifiable, albeit in small part.

For example, it is highly probably that a Greek warrior named Achilles have fought in the Trojan War, but that he was invulnerable save for his heel? Well, that is the stuff that myths are made of.

An example of a vaccine myth that once carried an element of truth but was shown to be invalid is the now-certified-as-myth belief that mercury present in the preservative in many multidose vaccine bottles was a cause of autism. The truth is that large doses of methyl mercury can damage the CNS in growing children and it is true that the number of vaccines containing mercury had increased at the same time the incidence of autism was reported to be increasing. On the other hand, while methyl mercury poisoning can damage a growing brain, it does not cause any symptoms suggestive of autism. The type of mercury in the vaccines was a form of ethyl mercury which is much less toxic and more quickly cleared from the body as compared to methyl mercury.

Think of the difference between drinking 1 ounce of ethyl alcohol (as in in a glass of wine) versus an ounce of methyl alcohol (aka, wood alcohol); the latter is a fatal dose in many humans whereas the former, is likely to be followed by several more. When all the pediatric vaccines were made mercury-free (with the exception of multidose flu vaccine), no change was seen in the incidence of autism, totally refuting the myth that thimerasol, the mercury-containing preservative, was the reason for the jump in autism rates.

Myths abound, too, about contraindications to specific vaccine administration. In the following scenarios, pick out the real contraindication to administration of the vaccine from among the 3 myths.

1. Zoster vaccine should NOT be given in which of the following situations:

A. Recipient’s spouse is receiving intensive chemotherapy.

B. Vaccine recipient is RN working in tertiary level newborn intensive care unit.

C. Recipient is currently taking 0.5 mg/kg /week of methotrexate for her rheumatoid arthritis

D. Recipient has a history of severe contact dermatitis to topical neomycin (a component in the vaccine).

Answer, discussion, and next question>>>


Answer: C. Recipient is currently taking 0.5 mg/kg /week of methotrexate for her rheumatoid arthritis – and should not receive the zoster vaccine.

Options A and B concern the question of whether or not a recipient of the live vaccine be around immunosuppressed persons. The PI for the zoster vaccine does say in its Warnings section that transmission of the virus is possible from vaccinee to a susceptible recipient. However, the CDC specifically says that those with chronic illnesses or immunosuppression can be around zoster vaccine recipients.

Option C requires answers to two questions. First, can the live zoster vaccine be given to an immunosuppressed individual? The answer is no. The second question is, at what dose methotrexate cause significant immunosuppression? The CDC suggests that a dose of less than 0.4 mg/kg/week of methotrexate is safe for a zoster vaccine recipient. Thus the dose of 0.5 mg/kg per week renders this woman immunosuppressed in the eyes of the CDC.

A student applying to nursing school comes to your office for an MMR and PPD. She has been trying unsuccessfully to become pregnant for about 6 months and her LMP was 3 weeks ago. She is on a daily dose of prednisone for Addison disease and nasal steroids for allergic rhinitis. She is willing to go on birth control for 3 months if you elect to give her the MMR vaccine today.

2. You tell her:

A. You cannot receive a PPD and MMR on the same day. The MMR can cause a false negative PPD test.

B. You cannot receive the MMR vaccine without a pregnancy test first.

C. You cannot receive an MMR injection because of the oral prednisone you take; the nasal steroids are not a concern.

D. You can receive the MMR and PPD today and will need to return in 48-72 hours to have the PPD read.

Answer and discussion>>>


Answer: D. You can receive the MMR and PPD today and will need to return in 48-72 hours to have the PPD read.

An MMR can cause suppression of a PPD response for about 4 weeks but not if both are given on the same day.

Routine pregnancy testing is not recommended in women of child bearing age, but of course, is fine to do in the judgment of the provider. At the same time MMR should not be administered to a pregnant female based on the theoretical concern regarding congenital rubella syndrome (CRS). Reassuringly, among more than 700 women who had received the MMR vaccine in their first trimester, the high risk time for CRS following natural infection, none of the babies showed any evidence of malformations compatible with CRS.

An immunosuppressed individual should not receive a live vaccine like MMR. A daily replacement dose for Addison disease is not immunosuppressive.


A list of invalid reasons to not immunize an individual with a specific vaccine

Zostervax PI with list of contraindications