This problem is addressed by PRISMA-S, AMSTAR 2 (Q3), ROBIS (P2 D2), and MECIR ((C3 & C26). Data on harms, adverse events or side effects are often not reported in full in the published academic papers for trials. The full side effect profiles for clinical trials will be available through each trial's clinical study report which should be consulted in order to learn the full adverse event profile recorded. There is a dedicated PRISMA extention for systematic reviews of harms.
Articles that support this problem:
Some improvements are apparent in identifying adverse effects in systematic reviews from 1994 to 2011
2013 : Journal of clinical epidemiology
Poor reporting and inadequate searches were apparent in systematic reviews of adverse effects
2008 : Journal of clinical epidemiology
Most systematic reviews of adverse effects did not include unpublished data
2016 : Journal of clinical epidemiology
Assessing harmful effects in systematic reviews
2004 : Bmc medical research methodology
Effect of reporting bias on meta-analyses of drug trials: reanalysis of meta-analyses
2012 : Bmj
Challenges in systematic reviews that assess treatment harms
2005 : Annals of internal medicine
Availability of large-scale evidence on specific harms from systematic reviews of randomized trials
2004 : The american journal of medicine
The Cochrane HPV vaccine review was incomplete and ignored important evidence of bias
2018 : Bmj evidence-based medicine
Selective reporting bias of harm outcomes within studies: findings from a cohort of systematic reviews
2014 : Bmj
Room for improvement? A survey of the methods used in systematic reviews of adverse effects
2006 : Bmc medical research methodology
Quality of reporting in systematic reviews of adverse events: systematic review
2014 : Bmj : british medical journal
Comparison of search strategies in systematic reviews of adverse effects to other systematic reviews
2014 : Health information & libraries journal