Cloth/fabric resembling cows. cattle or any of the animals of the Bovinae subfamily.

Bovine = of or pertaining to the subfamily Bovinae, which includes cattle, buffalo, and kudus.

For instance: A table cloth:
http://www.simplybovine.com/products/cowprinttablecloth.php

Looking at the definitions of the word "tela" and on finding this link which explains a vaccine of this type both in English and in Spanish, I came to the conclusion that they are talking about a membrane or outer membrane vaccine. However, I am not a specialist in this field and it is probably a wide guess so I would wait and see what other members can offer.

http://www.boos-bs.sk/us/vakciny.htm
http://www.boos-bs.sk/es/vakciny.htm

One of the translations for "tela" from the RAE is membrane:
http://buscon.rae.es/draeI/

tela1.
(Del lat. tela).
4. f. membrana (‖ tejido de forma laminar de consistencia blanda). Tela del cerebro, del corazón.