Table A: Evidence used to inform needle size recommendations for intramuscular injections made by National Immunization Technical Advisory Groups (NITAGs) in 4 countries
Country/NITAG	Evidence/publications cited to support needle size recommendations
	Systematic reviews	RCTs or CCTs	Ultrasound studies of muscle and subcutaneous fat thickness	Other: e.g. guidelines, textbooks, editorials, opinion pieces, etc.
UK/JCVI (DoH UK 2012a)a	0	2 (Diggle 2000a; Diggle 2006)	1 (Poland 1997)	1 textbook (Plotkin 2008a) 1 guideline (VATF 2001) 1 editorial/opinion piece (Zuckerman 2000)
Ireland/NIAC (NIAC 2016)b	0	‐	‐	5 guidelines (CDC 2011; DoH UK 2012a; ATAGI 2013; AAP 2015; AHS 2015)
US/ACIP (Kroger 2017)c	0	2 (Ipp 1989; Middleman 2010)	2 (Groswasser 1997; Poland 1997)	2 editorials/opinion pieces (Bergeson 1982; Zuckerman 2000)
Australia/ATAGI (ATAGI 2016)d	0	3 (Diggle 2000a; Diggle 2006; Ipp 1989)	3 (Groswasser 1997; Poland 1997; Cook 2006)	1 guideline (CDC 2011)
ACIP: Advisory Committee on Immunization Practices; ATAGI: Australian Technical Advisory Group on Immunisations; CCT: Controlled Clinical Trial; JCVI: Joint Committee on Vaccines and Immunisation; RCT: Randomised Controlled Trial. NIAC: National Immunisation Advisory Committee. aSee the section of the guidance entitled "Choice of needle size" (pp 29‐30). bSee the bibliography of Chapter 2 of the guidance entitled "General Immunisation Procedures". No references are cited in the main text of Chapter 2, therefore it is impossible to state precisely which of the publications listed in the bibliography have been used to support specific needle size recommendations. cSee Section 6 of the guidance entitled "Vaccine administration" (pp 82‐107). dSee Section 2.2.5 of the guidance entitled "Vaccine injection techniques" and Table 2.2.2.