• First of all, let try to draw a line between systematic review and meta-analysis. systematic seeks to collate evidence that fits pre-specified eligibility criteria in order to answer a specific research question. They aim to minimize bias by using explicit, systematic methods documented in advance with a protocol. While Meta-analysis is the statistical combination of results from two or more separate studies, if these are similar or homogeneous.

@ Ebrahim Endris, Yes, I agree with other colleagues. In addition, you can avoid primary collection if you get answer(s) of your research question(s) from meta-analysis.

Yes, It recommended but you have to aware and make stronger on the methods. it need attention more detail.