Of course, anti-vaccine folks are wrong when they say that vaccines don’t work.

Vaccines work and they work well to protect us from many different vaccine preventable diseases.

At least they do when you get the right vaccine at the right time and it is given properly. If an error is made, sometimes a vaccine dose needs to be repeated.

When a Vaccine Doesn’t Count and Needs to Be Repeated

While it would be unfortunate to have to repeat a vaccine dose, in most cases, if you didn’t, it would leave the child without full protection.

Why might a vaccine dose not count?

Although it doesn’t happen often, it is possible that:

• the wrong vaccine was given
• the vaccine was given too early, either before the next dose was due or when the child was too young. Although there is some leeway for when most vaccines can be given, there are still some specific rules to follow, especially the minimum time between doses, the earliest age you can get a dose, and the age requirement for booster doses. (sticking to the standard immunization schedule can help avoid these types of errors)
• the vaccine was mixed improperly (many vaccines are now premixed, making this error less likely to occur)
• part of the vaccine leaked out when it was being injected, which can happen when kids move, if they aren’t being held well as the shot is being given (rotavirus doses aren’t repeated if a child spits up though)
• the vaccine had expired or had not been stored properly
• two live vaccines (except for the typhoid vaccine) were given on separate days, but less than 28 days apart (again, sticking to the standard immunization schedule can help avoid this types of error)
• the vaccine was given by the wrong route, although depending on the vaccine, this dose might still be valid (most vaccines, except hepatitis B and rabies)

Still, instead of a vaccine dose not counting, the much more common reason for a vaccine dose to be repeated is for folks to lose their vaccine records.

Do You Really Have to Repeat That Vaccine Dose?

Are you worried now that your kids might get a vaccine dose that has to be repeated?

Don’t be. It doesn’t happen very often.

It helps that we don’t actually have a one-size-fits-all immunization schedule and

• there is a range of recommended ages for most vaccines
• there is a range of recommended ages for catch-up immunization, which is basically an accelerated immunization schedule, which is why infants can typically start getting their vaccines as early as age 6 weeks and get the first few sets as early as 4 weeks apart

Also, you typically have a grace period, during which early vaccine doses will still count.

“…administering a dose a few days earlier than the minimum interval or age is unlikely to have a substantially negative effect on the immune response to that dose. Known as the “grace period”, vaccine doses administered ≤4 days before the minimum interval or age are considered valid…”

AICP on Timing and Spacing of Immunobiologics

The grace period doesn’t count for the rabies vaccine and while it is an ACIP guideline, it might be superseded by local or state mandates. The grace period also can’t be used to shorten the interval between two live vaccines, which must be at least 28 days.

One last way to get away without repeating an invalid dose would be checking your child’s titers.

When Do You Repeat the Invalid Vaccine Dose?

The next question that comes up after you realize that you have to repeat a dose of a vaccine is when should you repeat it?

It depends.

• give the correct vaccine as soon as possible if the problem was that the wrong vaccine was given
• repeat the dose as soon as possible if the problem was an expired, improperly stored, or a dose that had leaked out
• if the dose was given too early, then you need to wait for the appropriate interval or when your child is old enough to get the dose. Keep in mind that when you repeat the dose, you would generally restart counting your interval from the invalid dose, not from the previous dose. That’s because the invalid dose might interfere with mounting a good immune response.

And in all cases, report the error to the ISMP National Vaccine Errors Reporting Program (VERP) or VAERS.

What to Know About Vaccine Errors

Although they aren’t common, vaccine errors sometimes lead to the need to repeat your child’s vaccines.

More on Vaccine Errors

• Know the “7 Rights” of Vaccine Administration
• Ask the Experts About Administering Vaccines
• Don’t Be Guilty of These Preventable Errors in Vaccine Administration!
• To Err Is Human; Not To Err Is Better!
• Tips for Finding Vaccine Records
• CDC – Vaccine Administration
• AICP – Timing and Spacing of Immunobiologics
• Administering Just the Diluent or One of Two Vaccine Components Leaves Patients Unprotected
• Confusion abounds! 2-year summary of the ISMP National Vaccine Errors Reporting Program (Part I)
• Recommendations for Practitioners to Prevent Vaccine Errors Part 2: Analysis of ISMP Vaccine Errors Reporting Program (ISMP VERP)
• ISMP National Vaccine Errors Reporting Program: One in Three Vaccine Errors Associated with Age-Related Factors
• First Annual Review of Data Submitted to the ISMP National Vaccine Errors Reporting Program (ISMP VERP)
• DTaP, LAIV, MCV4, PPSV23, HZV, 9vHPV… Alphabet Soup Vaccine Abbreviations and Acronyms Lead to Errors
• Recommendations for Practitioners and Manufacturers to Address System-Based Causes of Vaccine Errors