This is, in fact, done. Many flu vaccines are labeled "quadrivalent", which means that they provide antigens for four different flu strains. Similarly, the new (for Fall 2022) "bivalent" Covid vaccine boosters encode proteins for both the original Wuhan strain and Omicron. Gardasil-9 provides protection against nine different strains of HPV.
RobertColumbia t1_itbft1k wrote
Reply to comment by ConnieHormoneMonster in What is the greatest difficulty in creating a vaccine against leptospirosis for humans, being that there is already a vaccine for animals? by Artreides
This is, in fact, done. Many flu vaccines are labeled "quadrivalent", which means that they provide antigens for four different flu strains. Similarly, the new (for Fall 2022) "bivalent" Covid vaccine boosters encode proteins for both the original Wuhan strain and Omicron. Gardasil-9 provides protection against nine different strains of HPV.