Calves vaccinated at six weeks of age had a stronger response to the vaccine than calves vaccinated at two weeks of age, according to University of Vermont research.

Researchers Jeevan Patlola and Julie Smith measured the calves’ response three weeks post-vaccination. They found that calves vaccinated at six weeks of age had more white blood cells and more cells displaying immunoglobulins specific to the vaccine, compared to calves vaccinated at two weeks of age. 

The research reinforces the recommendation that vaccinations must be timed to match when calves are most likely to respond. Calves rely on passive immunity from their dams early in life. In those first few weeks, their own immune systems are not fully functional, and are rarely capable of responding to a challenge, whether it is by a real infection or a vaccine.