Infections such as measles, mumps and rubella are more severe in adults than in children.
Therefore, there is some concern that adults might be at risk if immunity from childhood
vaccination wears off. Natural infections with measles, mumps and rubella do induce
lifelong immunity. Vaccination also produces very long-lasting immunity. Immune
memory resulting from vaccination seems to persist even if there is no antibody
detectable in the blood. The occurrence rate of measles, mumps and rubella among those
who were the first to be vaccinated has not been affected by the passage of time.
Diphtheria and tetanus are somewhat different. Protection against these diseases requires
the actual presence of antibody in the blood at the time a person is exposed to the toxin.
Even though immune memory lasts 40 years or more after vaccination, antibody levels
decrease over time. These infectious toxins are so potent that disease can occur before the
immune system has time to respond. Adults must receive boosters every 10 years to be
protected against diphtheria and tetanus. |