This page provides more information about handling errata (corrections) and retractions.
According to Cochrane, Chapter 4, Section 4.6:
...it is important to be aware that some studies may have been found to contain errors or to be fraudulent or may, for other reasons, have been corrected or retracted since publication...Review authors should examine any relevant retraction statements and errata for information (MECIR Box 4.4.e)...
Errata is effectively an amendment that has been attached to a publication to identify and correct an error in the original publication. These tend to have little to no effect on the usefulness or validity of a study. Therefore, finding an errata does not necessarily mean the study should be excluded from a synthesis.
According to Cochrane 4.4.6, "...errata are published to correct unintended errors (accepted as errors by the author(s)) that do not invalidate the conclusions of the article."
Often, the main publishing site of an article with errata (accessible via the references DOI) will include a notice at the top of the page, such as the one seen below:
The "Errata" is identified as simply a 'correction', and includes both the date of the published errata and a link to that errata statement.
Note: You may have noticed that this is the PRISMA-P guideline we use to guide protocol development. The errata does not identify a problem so significant that the material is no longer useful - the errata is simply correcting a reporting error in one of their citations.
In contrast to errata, retractions usually indicate a meaningful issue or set of issues have been identified. It is not appropriate to rely upon the findings of a study that has been retracted. In the case of a systematic review, you would not want to include retracted research in your final synthesis - although you should document the reason for exclusion and/or consider discussing the implications of retracted studies in your discussion.
According to Cochrane 4.4.6, "Retractions are defined by the Committee on Publication Ethics (COPE) Council's retraction guidelines (Committee on Publication Ethics (COPE) Council 2019) as '...a mechanism for correcting the literature and alerting readers to articles that contain such seriously flawed or erroneous content or data that their findings and conclusions cannot be relied upon...'"
For additional resources about retractions, check out Amy Riegelman and Caitlin Bakker's entry in the Association of College and Research Libraries (ACRL) newsmagazine, Understanding the Complexities of Retractions (2018).