Asthma worsening was documented in 18 studies sourced from 16 published articles: The incidence of this AE was significantly lower in patients (13.31%, 583/4379) receiving anti-IL-5 treatment compared to those (19.99%, 822/4113) treated with a placebo (RR: 0.67, 95%CI: 0.61–0.73, P = 0.292, I2 = 11.5%). This evidence concerns the gene IL5 and asthma.