Nature 455, 532–536 (2008); doi:10.1038/nature07231

In this Letter, the heavy-chain sequence of 1F1 was in error and has been corrected in GenBank (EU169674.2). Also, the 1947 virus tested that was not inhibited by 1F1 should have been designated A/USA/L3/1947(H1N1) rather than A/Fort Monmouth/1/1947(H1N1). In addition, 1F1 exhibits HAI activity of 1.3 μg ml−1 (not undetectable) against A/Fort Monmouth/1/1947 virus. These errors do not affect our main conclusions. These errors have been corrected in the HTML and PDF of the original paper (particularly Table 1 and Fig. 1) and in the original Supplementary Information.