Table 1

Overview of included studies

AuthorYearCountryStudy inclusion periodStudy typeTotal NVaccinationPlacebo/ No vaccinationAge range at time of surgical treatment (years) Jadad Score
VaccinatedUnvaccinated
Hildesheim (22)2016USA2004–2005Post-hoc analysis nested in larger RCT 311 142 169 18–2518–253
Minors Score
Ghelardi (19)2018Italy2013–2017Prospective case-control trial 344 172 172 18–4518–4521
Garland (20)2016Australia2004–2006Post-hoc analysis nested in larger RCT 454 190 264 15–2515–2519
Kang (21)2013Korea2007–2010Retrospective case-control study 737 360 377 21–4520–4524
Joura (13)2012Austria2001–2003Post-hoc analysis nested in larger RCT 1066 474 592 15–2615–2524