| Scheduling Vaccines |
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| Why are
vaccines generally not given to infants
younger than 6 weeks of age in the U.S.? |
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| Mainly because
little safety or efficacy data exist on doses
given before 6 weeks of age, and the vaccines
aren't licensed for this use. The data that
exist suggest that the response to doses given
before 6 weeks is poor and in some cases (such
as Haemophilus influenzae type b [Hib]
vaccine) the response could be detrimental to
the infant by possibly reducing the immune
response to subsequent doses of Hib conjugate
vaccine. Hepatitis B vaccine is an exception
because infants respond adequately to this
vaccine as early as the day of birth and early
receipt of this vaccine is necessary to
protect infants born to HBsAg-positive
mothers. |
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| Is it
necessary to start a vaccine series over if a
patient doesn't come back for a dose at the
recommended time, even if there's been a year
or more delay? |
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| For routinely
administered vaccines, there is no vaccine
series that needs to be restarted because of
an interval that is longer than recommended.
In certain circumstances, oral typhoid vaccine
(which may be given for international travel)
needs to be restarted if the vaccine series
isn't completed within the recommended time
frame. |
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| What is meant
by "minimum intervals" between vaccine doses? |
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| Vaccination
schedules are generally determined by clinical
trials, usually prior to licensure of the
vaccine. The spacing of doses in the clinical
trial usually becomes the recommended
schedule. A "minimum interval" is shorter than
the recommended interval between doses, and is
the shortest time between two doses of a
vaccine series in which an adequate response
to the second dose can be expected. The
concern is that a dose given too soon after
the previous dose may reduce the response to
that dose. The minimum spacing between doses
is generally included in the ACIP
recommendation for that vaccine which can be
found at
www.cdc.gov/vaccines/hcp/acip-recs/index.html.
In addition, an extensive listing of
recommended and minimum intervals
and ages for vaccination can be found in the
ACIP General Best Practices Guidelines for
Immunization, available at
www.cdc.gov/vaccines/hcp/acip-recs/general-recs/timing.html#, Table 3-1. |
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| In updating
immunizations for immigration ("green card")
exams, I regularly come across intervals between catch-up vaccine doses that are
shorter than
ACIP recommendations—most often the last 2
doses of IPV are given less than 6 months
apart, but also sometimes the 2 doses of
varicella are given less
than 3 months apart, and the next-to-last and
last Td are given less than 6 months apart.
How significant is this in terms of immunity? |
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| The significance
of non-standard intervals probably depends on
the vaccine and the dose. This is a complex issue—studies have not been done to
examine the effect of various intervals
between doses on the immunogenicity of those
doses. But ACIP has examined the available
data and made
recommendations about the minimum acceptable
interval between doses for that dose to be
considered valid (there is no maximum interval
between
doses). These minimum intervals are published
as Table 3-1 in ACIP's General Best Practice
Guidelines on Immunization, available at
www.cdc.gov/vaccines/hcp/acip-recs/general-recs/timing.html.
Doses with a minimum interval less than the
recommended minimum, as described in Table
3-1, should not be counted as valid. More
details on this topic can be found in the General Best Practice
Guidelines. |
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| How can we
quickly determine how to "catch up" children
who have fallen behind on their shots? |
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| As a general
rule, infants or children who are more than 1
month or 1 dose behind schedule should be on
an accelerated schedule, which means the
intervals between doses should be reduced to
the minimum allowable. Catch-up schedules for
children ages 4 months through 18 years are
included with
each year's recommended immunization schedule
that is approved by the ACIP, CDC, AAP, and
American Academy of Family Physicians (AAFP).
To
obtain a copy, go to
www.cdc.gov/vaccines/schedules/hcp/index.html. |
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| When a
3-month-old infant presents having had no
prior immunizations, would you start the
accelerated schedule? |
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| The accelerated
schedule should be used when the child is more
than a month behind schedule, until you get
them caught up. An accelerated schedule is
acceptable as long as minimum ages and minimum
intervals are observed for each dose. Once you
have the child back on schedule, use the
recommended ages and intervals on the childhood schedule. In this case you can give
the child the first set of recommended
vaccines at age 3 months
and then bring him back at age 4 months and
give the second set of vaccinations. At this
point the child will be caught up and can
return to the usual
schedule. Be sure to educate the parents and
talk to them about the importance of bringing
the child back on time. |
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| If a child
falls behind on immunizations, is it
recommended to use only minimum intervals to
get the child caught up? Or should we use a
minimum interval
for the same vaccine only once? |
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| If a child is
behind on immunizations, the Advisory
Committee on Immunization Practices (ACIP)
recommends using the minimum intervals between
each
dose until the child is caught up. The minimum
interval for a vaccine can be used as many
times as necessary, until the child is back on
schedule. |
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| If two live
virus vaccines are inadvertently given less
than 4 weeks apart, what should be done? |
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| Two or more
injectable or nasally administered live
vaccines not administered on the same day
should be separated by at least 4 weeks to
minimize the
potential risk for interference. If two such
vaccines are separated by less than 4 weeks,
the second vaccine administered should not be
counted and the
dose should be repeated at least 4 weeks
later. Alternatively, one can perform
serologic testing to check for immunity, but
this option may be more costly,
may not be practical if multiple antigens are
involved (such as measles, mumps and rubella),
and may provide results that are difficult to
interpret. |
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| The
oral vaccines Ty21a typhoid, cholera and
rotavirus vaccines can be administered on the
same day with or at any interval before or
after other live
vaccines (injectable or intranasal). However,
oral cholera vaccine should be administered
before Ty21a vaccine, and 8 hours should
separate the oral
cholera vaccine and the first dose of Ty21a. |
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| We gave a dose
of vaccine too soon after the previous dose.
When can we give another (valid) dose? |
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| If vaccines are
given too close together, it can result in a
less than optimal immune response. However, in
most instances, a difference of a few days is
unlikely to have a negative effect on immune
response. With the exception of rabies
vaccine, ACIP allows a grace period of 4 days
(i.e., vaccine doses administered up to 4 days
before the recommended minimum interval or age
can be counted as valid). However, if a dose
was administered 5 or more days earlier than
the recommended minimum interval between
doses, it is not valid and must be repeated.*
The repeat dose should be spaced after the
invalid dose by the recommended minimum
interval. Note that for hepatitis A
vaccination, if the second dose is
administered too early and must be repeated,
the recommended interval between the invalid
dose and the repeat dose is 6 months; however,
if the repeat dose is administered earlier
than 6 months no further doses are recommended
as long as the interval between the first and
final dose is at least 6 months. |
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| If the first dose
in a series is given 5 days or more before the
recommended minimum age, the dose should be
repeated on or after the date when the child
reaches at least the minimum age. If the
vaccine is a live vaccine, ensuring that a
minimum interval of 28 days has elapsed from
the invalid dose is recommended. Avoid such
errors by knowing the minimum intervals and
ages for routinely given vaccines. You can
look up such information in the ACIP General
Best Practices Guidelines for Immunization,
available at
www.cdc.gov/vaccines/hcp/acip-recs/general-recs/timing.html#,
Table 3-1. |
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| The 4-day "grace
period" should not be used when scheduling
future vaccination visits, and should not be
applied to the 28-day interval between live
parenteral vaccines not administered at the
same visit. It should be used primarily when
reviewing vaccination records (for example,
when evaluating a
vaccination record prior to entry to daycare
or school). |
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| * The only
exceptions to this rule are the mRNA COVID-19
vaccines: ACIP does not recommend
administration of an additional dose following
an
incorrect dosing interval. |
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| Two live virus
vaccines can be given on the same day. How do
you define "day"? |
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| The "same day"
generally means at the same visit. This
interval has not been precisely defined and
probably will never be since it would be
extremely
difficult to study in order to develop an
evidence-based recommendation. Immunization
programs (and their computer systems) likely
define this
differently. It seems reasonable that if two vaccines were given on the same date then they
would both be valid. |
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| For the
purpose of vaccine spacing, what constitutes a
month: 28 days (4 weeks), 30 days, or 31 days? |
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| For intervals of
3 months or less, you should use 28 days (4
weeks) as a "month." For intervals of 4 months
or longer, you should consider a month a
"calendar month": the interval from one
calendar date to the next a month later. This
is a convention that was introduced on the
childhood schedule in 2002
and discussed in the paper "Evaluation of
Invalid Vaccine Doses" (Stokley S, Maurice E,
Smith PJ, et al. American Journal of
Preventive Medicine, 2004:
26[1]: 34–40). |
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| Does live oral
cholera vaccine need to be administered at an
interval from other live oral or injectable vaccines? |
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| In general, no.
According to ACIP's General Best Practice
Guidelines for Immunization, concerns about
spacing between doses of live vaccines not
given
at the same visit applies only to live
injectable or intranasal vaccines. So, live
oral cholera vaccine may be administered
simultaneously with another
vaccine, or at any interval before or after
administration of another vaccine. An
exception is that live oral cholera vaccine
should be administered before
live oral Ty21a typhoid vaccine, and 8 hours
should separate the oral cholera vaccine and
the first dose of Ty21a. |
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| The package
insert for VaxChora oral cholera vaccine
states that effectiveness and safety have not
been established for revaccination or for
individuals
with previous immunity. Does the CDC have any recommendations on revaccination or is one
dose considered lifetime immunity at this
time? |
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| At this time, CDC
does not have any recommendation related to
revaccination with oral cholera vaccine. The duration of immunity beyond 6 months
following one dose is unknown. As more
information becomes available, CDC will update
its recommendations accordingly. |
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| A 3-year-old
who was otherwise on schedule received some of
her 15-month vaccinations (MMR, DTaP, IPV)
twice due to a change in health plans. Can
these doses be counted toward kindergarten vaccinations? |
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| Whether these
doses count as part of the child's series
depends on the intervals between these doses
and the ones that preceded them. If the second
MMR was separated from the previous one by at
least 4 weeks, it can be counted as the second
MMR. No additional doses are indicated. The
4th dose of
IPV is recommended after the 4th birthday. In
this case, the child would need a fifth dose
of IPV on or after her fourth birthday. The
fifth dose of DTaP
should not be given earlier than age 4 years.
Assuming this dose of DTaP was the fifth the
child received, it was given much too early
and should not be
counted. The DTaP should be repeated on or
after the child's fourth birthday. |
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| If I give a
pneumococcal polysaccharide vaccine to my
patient now, how long must I wait before
giving the influenza or Td vaccine? |
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| Influenza vaccine
and Td (or Tdap) may be given at the same time
or at any time before or after a dose of pneumococcal polysaccharide vaccine. The
only time you have to wait is when two LIVE
vaccines are not given at the same visit; then
you need to wait at least 4 weeks to give the
second live vaccine. |
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| What interval
should be observed between receipt of a blood
product and vaccination with live attenuated influenza vaccine (LAIV; FluMist, AstraZeneca)? |
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| LAIV can be
administered at any time before or after
receipt of a blood product. See
www.cdc.gov/vaccines/hcp/acip-recs/general-recs/timing.html#,
Table 3-4, footnote B. |
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| Do any of the
bacterial vaccines that are recommended for
people with functional or anatomic asplenia need to be given before splenectomy? Do the
doses count if they are given during the 2
weeks prior to surgery? |
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Ideally, vaccination with both types of
pneumococcal (conjugate [PCV] and
polysaccharide [PPSV]), both types of meningococcal (MenACWY and
MenB), and Hib vaccine should all be completed
at least 2 weeks before a scheduled
splenectomy, if time permits. When preparing a
patient for
splenectomy, follow the dosing recommendations
for a patient who is already asplenic. |
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| Vaccine doses
administered within the two-week period before
surgery or after surgery are valid; however, administration at least two weeks before
surgery ensures the patient is protected from
the moment the spleen is removed. Completing
all doses preoperatively requires advanced
planning based
on the age and vaccination history of the
patient. If vaccinations cannot be completed,
administer as many as feasible at least 2
weeks prior to surgery.
Postponing splenectomy to complete vaccination
is not recommended. |
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| Because the most
likely vaccine-preventable threat to the
patient is from invasive pneumococcal disease,
CDC subject matter experts consider PCV the
highest priority vaccine to administer before
splenectomy. PPSV must be administered at
least 8 weeks after PCV. Splenectomy patients
require a two-dose primary series of MenACWY, given at least
8 weeks apart. Because the Menactra brand of
MenACWY may interfere with the immune response to
PCV, the first dose of Menactra in asplenic
patients should be delayed 4 weeks after PCV.
PCV may be administered at the same visit with
(or any time
before or after) Menveo or MenQuadfi brands of
MenACWY. The MenB primary vaccination series
requires 2-3 doses, depending upon the brand. |
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| If vaccines are
not administered before surgery, they should
be administered as soon as the person's
condition stabilizes post-operatively. |
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ACIP Recommendations
Vaccine Information Statements 
