Vaccine Mixology: Are All Diluents Made Equal?

June 14, 2017

True or False: some mixed vaccines have vaccine in the diluent and the powder. Answer and more questions in our short quiz.

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Let's see what you know about the liquid component of some vaccines.

1. Which of the following vaccines does not have to be reconstituted before administration?

A. Zostavax

B.  Menactra

C. Menveo

D. Hiberix

E. Rotarix

Answer, discussion, and next question>>

The answer is B. Menactra does not have to be reconstituted before administration

Menactra does not need reconstitution, all the others do. Ideally, all vaccines would need no mixing. Extra steps means extra chances for mistakes. Expiration dates need to be checked on both vials instead of just one. A diluent from a different vaccine may inadvertently be mixed with the intended vaccine. Multiple instances of diluents being injected without being mixed first have been reported. Rotarix diluent, designed for oral use, has also been injected IM by mistake.

Most diluents are simply water or saline. Two of the 14 vaccines requiring mixing have vaccine in the diluent as well as in the lyophilized powder.

2. Can you pick out which of the following sets of vaccines have active vaccine in both diluent and powder?

A. Pentacel and ProQuad

B. Pentacel and MenHibrix

C. Pentacel and Menveo

D. MMR and ProQuad

Answer, discussion, and next question>>


The answer is C. Pentacel and Menveo

Pentacel mixes a powdered Hib vaccine with the liquid DTaP-IPV and Menveo, a powdered MenA with a liquid MenCWY. 

What would you do in the following scenario? 

Your nurse, doing vaccine inventory at the end of the day, notices that 3 vials of Menveo powder are there, but sees only only 2 vials of the diluent. After a little research, you find that a 12-year-old patient that morning was inadvertently given the Menveo diluent containing vaccine against the C, W, and Y strains without mixing in the powdered A strain vaccine before administration. 

3. Do you:

A. Have the child return within 24 hours and repeat the properly mixed vaccine.

B. Inform the parent of the error but reassure them that it doesn’t matter unless the child travels overseas.

C. Have the child return in 30 days to repeat the vaccine in ensure an adequate immune response by avoiding “interference.”

D. Have the patient return and administer the powdered vaccine mixed with some normal saline.

Answer and discussion>>


The answer is B. Inform the parent of the error but reassure them that it doesn’t matter unless the child travels overseas

Option B is the best answer. What happens when the liquid portion that contains part of the vaccine is administered without first mixing in the powder? Do the vaccine components in the liquid portion “count?”  Fortunately, they do. Since meningococcal strain A does not circulate in the US and since that was the component in the powder, the child will not be at any significant increased risk of contracting meningococcal disease despite the error. However, it will be important to warn the parents that strain A does cause significant disease overseas, particularly in sub-Saharan Africa and if travel is planned, then the properly mixed vaccine should be administered at least two weeks before the trip.  If the parents or situation suggested that protections against the A strain is needed, then the repeat dose could be given at any time.

The take home message:  when you are preparing a vaccine that has a diluent, to avoid errors, don’t be doing shots before you give a shot.


A list of vaccines with diluents from the Immunization Action Coalition.

Immunization Action Coalition. Ask the Experts: Diseases & Vaccines. Meningococcal ACWY Disease