Nat. Immunol.; doi:10.1038/ni.3328; corrected online 7 January 2016

In the version of this article initially published online, the location of Momenta Pharmaceuticals was incorrectly stated as Boston. It should read “Cambridge.” Also, in Table 1, the set of parentheses for HAI day 63 was incomplete. It should read “mean (s.d.).” The errors have been corrected for the print, PDF and HTML versions of this article.