Those born before 1957 are presumed to have been infected or exposed, which provides lifelong immunity. (health.com)
One may develop lifelong immunity after a single shot, while another may never develop full immunity without boosters. (cesarsway.com)
Some strains of distemper vaccine provide nearly lifelong immunity after the initial series and one - year booster while other strains provide a shorter duration of immunity. (vetinfo.com)