For most inactivated vaccines, what is true of the very first dose given?

1. Inactivated vaccines need multiple doses over time to build ongoing immunity. 2. The first dose generally does not produce protective immunity; it primes the immune system instead. 3. A protective immune response develops after the second or third dose. 4. Later supplemental doses may still be needed to boost antibody titres, because they diminish with time, but they are not where protection begins. 5. Adjuvants improve immunogenicity where they are used, but they do not replace the second and third doses. _Source: CDC Epidemiology and Prevention of Vaccine-Preventable Diseases (Pink Book), section Inactivated Vaccines_