7. Varicella: effectiveness ‐ cohort studies.

Study	Population characteristics	Case definition	Vaccine/strain	N vaccinated sample size (dose)	N control	N events in exposed/ N exposed or person‐months versus N events in non‐exposed/ N non‐exposed or person‐months	VE% (95% CI)
ca‐Giaquinto 2018	Children aged 0 to 14 registered with 35 Pedianet database physicians across Italy between 1 October 1997 and 30 September 1998	Varicella cases recorded in the Pedianet databases are based on physician confirmation only (no laboratory tests were performed).	MMRV: vaccine ProQuad	n = 2357	n = 912 unvaccinated	43/2357 versus 287/912	unadjusted estimate 94% (92% to 96%) adjusted estimate 94% (91% to 95%) VE = (1 −RR) x 100
ca‐Rieck 2017	Between January 2006 and October 2013, n = 1,449,411 children	4‐step algorithm to only select confirmed and incident varicella cases. Step 1: excluded incompatible or implausible coding combinations for varicella diagnosis reliability; step 2: excluded observations with diagnosis reliability other than confirmed (i.e. suspected, excluded, recovered); step 3: excluded observations with diagnosis type other than incident (i.e. previous state, unknown, not provided); step 4: limited the data selection to the earliest ICD‐10 code per patient whilst also keeping the information about the most severe ICD‐10 code (within up to one‐quarter following the initial diagnosis) using the following ranking (in descending order of severity): varicella with encephalitis, meningitis, pneumonia, other complications, no complications, no further details, with the last equalling ‘no complications’.	Since 2004, single‐dose varicella vaccination has been recommended for all children aged 11 to 14 months. 2 single‐compound varicella vaccines (VAR; Varivax, Sanofi Pasteur MSD; Varilrix, GSK) were initially available. In 2006, a combined (MMR)‐varicella vaccine (MMRV; Priorix‐Tetra, GlaxoSmithKline) was licenced with a 2‐dose schedule. A 2‐dose schedule has been recommended since 2009 targeting children with the second dose at age 15 to 23 months. Since 2011, the first immunisation has been given preferably as 2 separate injections of VAR and MMR due to higher rates of febrile seizures following immunisation with MMRV. (a) 1 dose MMRV (b) 2 doses MMRV	‐	‐	‐	VE = (1 − HR) x 100 adjusted estimate (a) 81.7% (81.0% to 82.4%) (b) 94.4% (94.2% to 94.6%) ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ VE = (1 −RR) x 100 RR obtained from HR and attack rate of varicella in unvaccinated children, Risk in unvaccinated children = 9% (a) 61.8% (60.6% to 63.0%) (b) 86.6% (86.1% to 87.0%)
ca‐Spackova 2010	1084 children attended day‐care centres in Germany	Varicella was classified clinically as mild (< 50 skin lesions), moderate (≥ 50 skin lesions), severe (any hospitalised case).	MMRV Priorix‐Tetra (a) All‐brand doses (b1) All‐brand 1 dose (b2) All‐brand 2 dose ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ (c) Varivax 1 dose (d) Varilrix 1 dose (e1) Priorix‐Tetra 1 dose (e2) Priorix‐Tetra 2 doses ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ (f1) Mild disease (f2) Moderate disease	(a) n = 244 (b1) n = 167 (b2) n = 77 (c) n = 48 (d) n = 77 (e1) n = 38 (e2) n = 56 (f1) n = 233 (f2) n = 221	n = 108 (f1) n = 71 (f2) n = 93	(a) 33/244 versus 52/108 (b1) 31/167 versus 52/108 (b2) 2/77 versus 52/108 (c) 4/48 versus 52/108 (d) 19/77 versus 52/108 (e1) 7/38 versus 52/108 (e2) 2/56 versus 52/108 (f1) 22/233 versus 15/71 (f2) 10/221 versus 37/93	(a) 71% (57% to 81%) (b1) 62% (43% to 75%) (b2) 94% (75% to 98%) ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ (c) 86% (56% to 96%) (d) 56% (29% to 72%) (e1) 55% (8% to 78%) (e2) 91% (65% to 98%) ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ (f1) 53% (14% to 75%) (f2) 89% (78% to 95%) adjusted for confounders VE = (ARU − ARV)/ARU x 100 Orenstein 1985 VE = (1 − RR) x 100
ca‐Tafuri 2013	Children at (a) preschool (b) elementary school (c) all ages	Reported by parents	MMRV (Priorix‐Tetra) Varicella OKA; 1 dose	(a) n = 170 (b) n = 71 (c) n = 241	(a) n = 40 (b) n = 287 (c) n = 327	(a) 2/170 versus 14/40 (b) 2/71 versus 223/287 (c) 4/241 versus 237/327	(a) Not reported (b) 69.2% (50.5% to 88.1%) (c) 59.9% (48.3% to 69.8%) VE = (ARU − ARV)/ARU x 100 Orenstein 1985 VE = (1 − RR) x 100

ARU: attack rate amongst unvaccinated
ARV: attack rate amongst vaccinated
CI: confidence interval
ICD‐10: International Classification of Diseases, Tenth Revision
HR: hazards ratio
MMR: measles, mumps, rubella vaccine
MMRV: measles, mumps, rubella, and varicella vaccine
OR: odds ratio
PT: person‐time
RR: risk ratio (relative risk)
VE: vaccine effectiveness/efficacy