Effect of needle length on incidence of local reactions to routine immunisation in infants aged 4 months: randomised controlled trial
BMJ 2000; 321 doi: https://doi.org/10.1136/bmj.321.7266.931 (Published 14 October 2000) Cite this as: BMJ 2000;321:931
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Editor - Diggle & Deeks made no mention of aspiration before
injection of vaccine in their article on the effects of needle length. On
three occasions in very many immunisations, MB drew blood necessitating a
second prick - better a second prick than an intravenous immunisation with
possibly tragic outcome.
Pamela Wray,
Retired Physician,
30 Constable Rd., Ipswich, IP4 2UW
Maxine Blau,
School Nurse,
23 Constable Rd., Ipswich, IP4 2UW.
Diggle L., & Deeks J. Effect of needle length on incidence of
local reactions to routine immunisation in infants aged 4 months:
randomised controlled trial. BMJ 2000;321:931-933 (14th October)
Competing interests: No competing interests
Diggle and Deeks implicitly suggest that infants should be
routinely immunised with 25 mm long needles inserted into
the skin up to the hub.1
Use of 25 mm long needles might be detrimental to infants,
as I have personally not rarely seen: in lean infants, deep
insertion of 25 mm long needles can very painfully puncture
the periosteum and make the actual injection very difficult
or even impossible without slightly withdrawing the needle
into more extensible tissues, another potentially painful
movement.
Further, bone punctures can lead to osteomyelitis in
infants.2 Such a rare event might have gone undetected in
Diggle and Deeks' small study.
Diggle and Deeks'suggestions are too reductionnist. They
might well protect parents from perceiving local redness and
swelling in their immunised infants. They might as well put
infants at risk of having more painful immunisations or,
even worse although probably very rare, of developing bone
infections.
References
1 Diggle L., Deeks J. Effect of needle length on incidence
of local reactions to routine immunisation in infants aged 4
months: randomised controlled trial. BMJ 2000;321:931-3
2 Goldberg I, Shauer L, Klier I, Seelenfreund M. Neonatal
osteomyelitis of the calcaneus following a heel pad
puncture. Clin Orth
Competing interests: No competing interests
I would like to briefly comment on this interesting study. While it
is certainly comforting to see fewer local recations with the use of
longer immunization needles, one has to critically ask whether this is a
real advantage for the vaccinated child and not only for the observing
parents and caregivers. Possibly, the same degree of local inflammation –
the basis for erythema and inflammation at the injection site – may occur
with deeper injections but may simply be less visible and palpable
compared to the use of conventional, shorter immunization needles. In
order to better be able to see a real benefit for the child, one would
like to see the report on rates of other common adverse events following
immunization in infancy – such as fever, disturbed night sleep, poor
feeding, prolonged crying – in this study. A significant decrease of
occurrence of these less specific events, which obviously may interfer
with family peace for a few days, would be the ultimate proof of benefit.
The observed tendency of less tenderness (how was this assessed in young
infants?) appears to point into the right direction. However, a larger
study may be necessary to demonstrate significant differences.
Competing interests: No competing interests
We would like to address the recent responses to our paper concerning
differences in needle bore, the independence of the assessments, and the
effect of needle length of tenderness.
The two needles compared in our study are those that we observed
being used in general practice in a survey of 102 practice nurses involved
in infant immunisation in Oxfordshire. Nobody in our survey was using the
alternative 25G 25mm needle nor the 23G 16mm needle. Whilst we recognised
at the design stage of this study that it would be interesting to compare
both length and bore, we thought it more important to compare the needles
currently being used. Other studies (referenced in our paper) have
compared same bore needles of different lengths and have noted similar
findings to ours - hence we consider the observed difference more likely
to be related to needle length than needle bore, although additional
evaluation of the 25G 25mm needle might be considered.
It seems highly unlikely that the observed differences are
exaggerated through parental recording of reactions. The parents were not
told which needle was used to administer the vaccines to their child.
Whilst this blinding mechanism is not secure (a knowledgeable parent would
be able to visually identify the needles by the coloured hub), we have
plenty of anecdotal evidence to believe that any resulting bias of parents
or practice nurses would have been in favour of the smaller needle -
parents clearly perceive longer needles to be painful than shorter
needles. We agree that in an ideal world it would have been helpful for
an independent observer to have monitored reactions: in the real world
where we conducted this research the use of an independent observer to
visit each child's home on 4 occasions following each immunisation was not
feasible.
Interpretation of the non-significant difference in tenderness
between the needles must be made with caution. It would be wrong to
conclude from the non-significance of the finding that there was "evidence
of no difference"- the correct interpretation is that there was "no
conclusive evidence of a difference". In fact the data on tenderness also
show reductions of the same magnitude as the reduction in redness, but as
tenderness occurred less frequently the results were not formally
statistically significant.
To get an idea of the possibility that there really are increases in
tenderness it is possible to conduct Bayesian style analyses to calculate
probabilistic answers to the question "what are the chances that longer
needles do significantly increase or significantly decrease tenderness?"
The following analyses have been conducted using an "uninformative prior".
When designing the trial we considered that relative differences of 25% in
tenderness would be clinically significant. Based on the data at six
hours the probability that there is an increase in tenderness of at least
25% with the longer needle is only 2%. The chances that tenderness
actually reduces by at least 25% with a longer needle is 73%. So despite
the analysis not reaching formal levels of statistical significance, the
data give no support to the hypothesis that the superficial reactions
observed with the shorter needle are exchanged by deeper reactions with a
longer needle, and reasonable support to the conclusion that tenderness
will also be reduced by using a longer needle, as well as redness and
swelling.
Based on this data we advocate a change to the status quo and
advocate routine use of the 23G 25mm needle, and hope manufacturers will
supply these longer needles with their vaccine packs.
Competing interests: No competing interests
The authors claim that 25 gauge needles cause more severe local
reactions because they are shorter than 23 gauge needles. It is likely
that 25 gauge needles cause more trauma because they have a narrower bore
and not because they are shorter. The 25 gauge needle produces a jet under
higher pressure which causes much more local tissue damage. The 23 gauge
needles, whatever their length, produce less trauma and therefore less
severe local reactions.
Irrespective of underlying cause, the conclusion, that we should be
using 23 gauge needles, is the same. I welcome the authors' recommendation
that manufacturers should review their policy of supplying the 25 gauge
needles in vaccine packs.
Competing interests: No competing interests
I read with interest the study by Diggle and Deeks on needle length
and local reactions. The paper certainly could lead to an interesting
change in practice, although I do have several criticisms of the study and
would suggest that further research is required.
Firstly, I am surprised by the design of the study, as no attempt is made
to use equal bore sizes and hence remove this conflicting variable. As a
result, the conclusions are significantly weakened and the reader could
equally deduce that the effect was due to the different bore sizes and not
as the authors suggest the length.
Secondly, no independent observer was used to objectively assess redness,
swelling and tenderness. Instead parents were used, who were not blinded
in any way and could have varying interpretations of these parameters.
Finally, the study also fails to demonstrate any significant difference in
tenderness which from the babies point of view is the most important
factor. One could conjecture that the same local reaction occurs with both
injection types, causing equal tenderness, it is merely that one is closer
to the skin surface. It would have been of interest to know if the use of
analgesics differed between groups, or if any local reaction was
significant enough for it to require medical attention. Otherwise the
findings are only of dermatological significance, and not sufficient to
demand a change in practice.
Competing interests: No competing interests
thinner needles hurt less
This response is not about vaccinations, but about using
the 25 gauge 25mm needle to adminster intra-articular or
intralesional steroid injections for musculoskeletal
problems such as synovitis, tennis elbow, or carpal tunnel.
It has been my practice for many years to do this, usually
with ethyl chloride skin anaesthesia. The advantages are of
much reduced discomfort and bleeding, as compared with the
usual 23 gauge (blue) or 21 gauge (green). Obviously the
larger gauge is required for aspiration of fluid, but the
25mm length is adequate to inject most joints and soft tissue lesions.
Competing interests: No competing interests