Here are some possibilities:
* "Antiviral": This refers to substances or treatments that inhibit or destroy viruses.
* "Bivalent": This describes something having two valencies, often referring to vaccines that target two strains of a virus.
* "Trivalent": This describes something having three valencies, also often referring to vaccines.
* "Multivalent": This describes something having multiple valencies, typically referring to vaccines targeting multiple strains or serotypes.
If you could provide more context or the source where you encountered the term "antivalent," I might be able to give you a more precise answer.
