Which Salmonella enteritidis vaccine, given to chicks, provides longer and stronger protection?

• A. Killed vaccine
• B. Live vaccine
• C. Subunit vaccine
• D. DNA vaccine

Answer: (B)

Giving a Salmonella enteritidis vaccine to chicks, a live attenuated vaccine tends to provide longer and stronger protection because it replicates in the host and presents the antigens in a way that closely mimics natural infection. This replication stimulates both humoral and cell-mediated immunity and promotes robust mucosal immune responses in the gut-associated lymphoid tissue, which are crucial for defending against enteric pathogens. The result is durable memory, higher levels of protective IgA at mucosal surfaces, and better control of intestinal colonization and shedding.

Killed vaccines, while safer, mainly induce systemic antibody responses and often require boosters; they generally don’t induce as strong mucosal or cell-mediated immunity, so protection tends to be shorter-lived. Subunit vaccines are very safe but can be less immunogenic on their own and rely on adjuvants to boost duration and breadth of protection. DNA vaccines can generate strong responses, but their practical use in poultry for long-term protection has been limited, and they may not consistently yield the same duration of protection as a well-attenuated live vaccine in chicks.

Thus, the live attenuated vaccine provides the best combination of robust, longer-lasting protection and effective mucosal immunity for chicks.