Pregnant women are a WHO priority group for influenza vaccination, but evidence from observational studies in pregnancy is subject, among others, to the healthy-vaccinee bias, overestimating the vaccine effectiveness and safety. An USA survey adds new evidence that documents this bias. Therefore, it is essential to assess vaccine effectiveness and safety with RCTs. Cochrane reviews identified one RCT with “low risk of bias”, in a medium-income country, with NNV 55 for mothers. Its data show an excess of local adverse effects, and a tendency to harm for serious adverse events, with uncertain or very limited protection against influenza.