How to keep the abbreviation dot in journal field of bibtex?

The abbreviation dot in journal field was omitted. How can I maintain it?

Here is my main.tex:

begin{document}
...
bibliographystyle{vancouver.bst}
bibliography{abbr.bib}
end{document}

In abbr.bib file:

@Article{buchfink2015fast,
  author    = {Buchfink, Benjamin and Xie, Chao and Huson, Daniel H},
  journal   = {Nat. Methods},
  title     = {Fast and sensitive protein alignment using DIAMOND},
  year      = {2015},
  number    = {1},
  pages     = {59--60},
  volume    = {12},
  publisher = {Nature Publishing Group},
}

Compile:

Buchfink B, Xie C, Huson DH. Fast and sensitive protein alignment using
DIAMOND. Nat Methods. 2015;12(1):59–60

I Expect ‘Nat. Methods.‘ not ‘Nat Methods.’