Read "Ask the Experts" Q&As from CDC experts
Many readers of Needle Tips,
Vaccinate Adults, and Vaccinate Women
consistently rank "Ask the Experts" as their favorite feature in
these publications. As a thank-you to our loyal IAC Express
readers, we have decided to periodically publish an Extra Edition
with new "Ask the Experts" Q&As answered by CDC experts.
Back to top
IAC thanks William L. Atkinson, MD, MPH, and Andrew T. Kroger, MD,
MPH, medical epidemiologists at the National Center for
Immunization and Respiratory Diseases, CDC, for agreeing to answer
the following questions.
Editor's note: Information about submitting a question to "Ask the
Experts" is provided at the end of this IAC Express article.
A 60-year-old patient was given varicella vaccine instead of zoster
vaccine. Should the patient still be given the zoster vaccine? If
so, how long an interval should occur between the 2 doses?
ACIP states the following: "If a provider mistakenly administers
varicella vaccine to a person for whom zoster vaccine is indicated,
no specific safety concerns exist, but the dose should not be
considered valid and the patient should be administered a dose of
zoster vaccine during that same visit. If the error is not
immediately detected, a dose of zoster vaccine should be
administered as soon as possible but not within 28 days of the
varicella vaccine dose to prevent potential interference of 2 doses
of live attenuated virus."
To download the ACIP recommendations titled "Prevention of Herpes
Zoster," go to: http://www.cdc.gov/mmwr/PDF/rr/rr5705.pdf
We mistakenly administered the Boostrix brand of Tdap to a 52-year-old patient instead of the Adacel brand of Tdap. Should the dose of
Boostrix be counted as valid?
Currently, only Adacel Tdap (sanofi pasteur) is licensed and
recommended for use in adults (Adacel is licensed for persons age 11-64 years). Boostrix Tdap (GlaxoSmithKline) is licensed for
persons age 10–18 years.
According to ACIP, if Boostrix is administered in error to an adult
age 19 or older, this dose should count as the Tdap dose and the
patient should NOT receive an additional dose of Tdap (Adacel). The
patient should be informed of the medical error in vaccine
To help prevent inadvertent administration of Boostrix when Adacel
is indicated, vaccine providers should examine the product labels
carefully before administering these vaccines.
Can the parents of a newborn receive a dose of Tdap right after
their child's birth to protect themselves and, indirectly, their
newborn from pertussis, even though they had a dose of Td vaccine
less than 2 years ago?
Yes. Parents should receive a single dose of Tdap as soon as
possible to protect the baby from pertussis. If a dose of Td was
given within the previous 2 years, parents should still be
vaccinated with Tdap as soon as possible regardless of the time
interval since the last dose of Td. Other household contacts who
are not up to date with their pertussis-containing vaccinations
should also be appropriately vaccinated.
How soon after receiving a dose of Td can a healthcare worker
receive a dose of Tdap in order to protect vulnerable infants and
If they have not previously received Tdap, healthcare personnel in
hospitals and ambulatory care settings who have direct patient
contact should receive a single dose of Tdap as soon as feasible
and without regard to the dosing interval since the last Td. There
is no "minimum interval" one needs to wait between receiving Td and
Tdap when it is given to protect infants or other vulnerable
If a college student previously had 2 pediatric doses of hepatitis
A vaccine, does he or she need a third dose as an adult?
No. A person is considered immune as long as she or he received 2
age-appropriate doses of hepatitis A vaccine (given at least 6
months apart) prior to age 19 years. There is no "booster" dose
If a woman's rubella test result shows she is "not immune" during a
prenatal visit but she has 2 documented doses of MMR vaccine, does
she need a third dose of MMR vaccine postpartum?
ACIP does not routinely recommend more than 2 doses of MMR vaccine.
A negative serology after 2 documented doses probably represents a
false negative (i.e., antibody titer too low to detect with
commercial tests). If a person is found to have a negative serology
after 2 documented doses of MMR, it is best to stop testing for
ACIP's recommendations for the use of MMR vaccine can be accessed
What is the significance of the difference in the abbreviations for
the vaccines DTaP (for children less than age 7 years) and Tdap
(used in adolescents or adults)?
Both vaccines provide protection against diphtheria, tetanus, and
pertussis, but DTaP has MORE diphtheria toxoid (3-5 times as much)
and MORE pertussis antigen than the amount in the Tdap vaccines.
This larger amount of antigen is reflected by the use of the
capital letters "D" and "P" when writing DTaP (the pediatric
vaccine). Because both DTaP and Tdap contain equal amounts of
tetanus antigen, both vaccine abbreviations contain a capital "T."
HOW TO SUBMIT A QUESTION TO "ASK THE EXPERTS"
IAC works with CDC to compile new "Ask the Experts" Q&As for our
publications based on commonly asked questions. We also consider
the need to provide information about new vaccines and
recommendations. Most of the questions are thus a composite of
You can email your question about vaccines or immunization to IAC
at email@example.com. As we receive hundreds of emails each month,
we cannot guarantee that we will print your specific question in
the "Ask the Experts" feature. However, you will get an answer. To
see if your question has already been answered, you can first check
the "Ask the Experts" online archive at
You can also email CDC's immunization experts directly at
firstname.lastname@example.org. There is no charge for this service.
If you have a question about IAC materials or services, email
Please forward these "Ask the Experts" Q&As to your co-workers and
suggest they subscribe to IAC Express at