Results of multilevel model for impact of experimental factors on PRNT75 estimates using cloglog regression.

(1) Marginal R2 that indicates the proportion of variance explained by the fixed effects only [31]. Model also adjusted for year of assay.The model has a random intercept for the viral strain and serum pool used in the experiment and is also adjusted for the year of the assay. All coefficients have been transformed by raising 10 to the power of the coefficient.