Correlation of infant age with neutralization of IAV by linear regression. Data shows linear regression analysis performed for (A,B) untreated or (C,D) RDE-treated saliva against (A,C) Udorn or (B,D) PR8 virus. Data-points represent the means of 19 untreated and 17 RDE-treated individual human infant saliva samples tested at least in triplicate. Indicated for each line of best fit are the regression coefficients ± standard error (P value indicative of the goodness of fit of data to the line). Below the figure, the results of pairwise tests of the similarity of the slopes of the lines are indicated.