ObjectiveTo systematically evaluate the efficacy and safety of probiotics for prevention of ventilator-associated pneumonia (VAP).MethodsThe Web of Science, Pubmed, OVID, Cochrane Library, CNKI, EMbase, Sciencedirect, Chinese biomedical database, and Wanfang database before August 2017 were searched, and the relevant data resources were also searched by hand to collect randomized controlled trials (RCTs) of probiotics for prevention of VAP. The quality of the included studies was evaluated using a modified version of the Jadad scale. Meta-analysis was performed with RevMan 5.3 software.ResultsA total of 16 RCTs were included. The use of probiotics can reduce the incidence of VAP [RR=0.71, 95%CI (0.62, 0.80), P<0.000 01], ICU days [MD=–3.28, 95%CI (–6.15, –0.41), P=0.03] and total duration of antibiotics [MD=–2.47, 95%CI (–4.89, –0.04), P=0.05], but can not reduce the mortality of ICU [RR=0.99, 95%CI (0.74, 1.32), P=0.94], hospital mortality [RR=0.77, 95%CI (0.58, 1.01), P=0.06], 28-day mortality [RR=1.01, 95%CI (0.69, 1.47), P=0.97], 90-day mortality [RR=1.00, 95%CI (0.72, 1.37), P=0.99], hospital stays [MD=–0.68, 95%CI (–3.88, 2.52), P=0.68], duration of mechanical ventilation [MD=–2.17, 95%CI (–4.78, 0.44), P=0.10], or the incidence of diarrhea [RR=0.96, 95%CI (0.80, 1.14), P=0.62]. No serious adverse events were reported in all included RCTs.ConclusionsThe use of probiotics can reduce the incidence of VAP, but it has no effect on the mortality, hospital stay, duration of mechanical ventilation or the incidence of diarrhea. However, considering the heterogeneity of research designs, we need more rigorous, large sample randomized controlled studies to increase the strength of evidence.