Needle length and local reactions to routine immunisations

Using a needle of 25 mm (either 23 G or 25 G) appears to causes fewer local reactions than a needle of 16 mm while achieving a comparable immune response to 25 G 16 mm needles for intramuscular vaccination in infants.

A Cochrane review included 5 studies with a total of 1350 subjects. The evidence from two small trials was insufficient to allow any confident statements to be made. The remaining 3 trials (n=1135) contributed data to comparisons between 25 G 25 mm, 23 G 25 mm, and 25 G 16 mm needles. These trials involved infants predominantly aged two to six months undergoing intramuscular vaccination in the anterolateral thigh. The vaccines administered were combination vaccines containing diphtheria, tetanus, and whole-cell pertussis antigens (DTwP). In some trials, the vaccines also contained Haemophilus influenzae type b (DTwP-Hib) and hepatitis B (DTwP-Hib-HepB) antigen components. There was little or no difference in immune response, defined in terms of the proportion of seroprotected infants, between using 25 G 25 mm, 23 G 25 mm, or 25 G 16 mm needles to administer a series of three doses of a DTwP-Hib vaccine (1 trial, n=309 to 402, moderate quality evidence. 25 mm needles (either 23 G or 25 G) lead to fewer severe local reactions (extensive redness and swelling) and fewer non-severe local reactions (any redness, swelling, tenderness or hardness (composite outcome)) after DTwP-Hib vaccination compared with 25 G 16 mm needles. One fewer infant assessed to experience a severe local reaction after the first vaccine dose for every 25 infants vaccinated with the longer rather than the shorter needle (number needed to treat (NNT) 25 (95% confidence interval (CI) 15 to 100)). One fewer infant was estimated to experience a non-severe local reaction at 24 hours after the first, second, and third vaccine doses for every five to eight infants vaccinated with the longer rather than the shorter needle (NNTs range from 5 (95% CI 4 to 10) to 8 (95% CI 5 to 34)) (moderate quality evidence, one trial for first and second doses, two trials for third dose, numbers of participants in analyses range from 413 to 528). 696 healthy infants were vaccinated at 2, 3, and 4 months of age, with follow-up to 5 months of age. Local reactions to diphtheria, tetanus, whole cell pertussis, H influenzae type b vaccinations decreased significantly with wide, long needles compared with narrow, short needles (e.g. after six hours of first dose RR 0.89, CI 0.79 to 1.01 and on day 3 RR 0.46, CI 0.27 to 0.80, and reactions after third dose respectively RR 0.92, CI 0.78 to 1.08 and RR 0.54 CI 0.34 to 0.85). Non-inferiority of the immune response was shown using a wide, long needle rather than a narrow, short needle for serogroup C meningococcal glycoconjugate vaccine and for diphtheria but not for H influenzae type b or tetanus, although no evidence was found of a decrease. Little difference was found between needles of the same length but different gauges in local reaction or immune response."?>