However, few studies have focused on this issue: Watanabe et al. have shown that vaccination of rhesus macaques for attenuated simian immunodeficiency virus resulted in the activation of NK cells by IL-15 [89]; another study has also demonstrated that the influenza vaccine improves cytokine-induced memory-like NK cells [90]; in individuals vaccinated for influenza, it has been observed that in the vaccine responders, the population of NK cells expressing NKG2C increased after vaccination [91]. Here, IL15 is linked to influenza.