Which type of vaccine requires two doses for optimal immunity?

The measles, mumps, and rubella (MMR) vaccine is designed to provide optimal immunity through two doses. The first dose is typically administered during early childhood, while the second dose is given later, often between ages four and six. This two-dose schedule enhances the immune response and ensures a higher level of protection against these diseases.

In contrast, the typhoid vaccine may require either one or multiple doses, depending on the type of vaccine used and individual circumstances. The pneumococcal vaccine can also be given in a one-dose format for certain types of pneumococcal vaccines while others may include multiple doses depending on age and health status. The influenza vaccine is recommended annually, with a single dose each year rather than a two-dose series for optimal immunity.