Retraction Note to: European Journal of Clinical Pharmacology (2019) 75:303–311

The Editor-in-chief and the authors retract the following article [1].

After publication, a reader has identified some mistakes in the data reported, these include the following:

  1. (i)

    Inclusion of studies which did not met strict inclusion criteria: one with pseudo randomization allocation [2] and another one with the intervention group receiving vitamin C and herbal preparation containing Echinacea and propolis [3] which is relatively heavily weighted and has one of the strongest effects in the analysis of primary and secondary outcomes.

  2. (ii)

    Some data, numbers of upper respiratory tract infection (URTI) episodes and standard-deviations of URTI durations, extracted from studies were erroneous.

  3. (iii)

    Some statistical approaches performed in our meta-analysis are not appropriate and have not been described accurately. These errors are likely to invalidate the results.

The authors acknowledge and apologize for these involuntary errors. For these reasons, the article has been retracted.