XK and influenza: The potency of NA‐specific antibodies in inhibition of NA catalysis was studied using an enzyme‐linked lectin assay (ELLA) (Figure 5 F).[33] NA inhibition is an independent correlate of protection against influenza in clinical trials.[31] VLP‐conjugated N1 showed potent NA inhibition, while none of the samples from immunization with free N1 showed detectable inhibition (Figure 5 I).