The latest news in the world of childhood infections is that there is a resurgence of mumps among young American teenagers and adolescents. Researchers believe that this is most likely because of the weakening of the vaccine.
The MMR vaccine, given in two doses to children, protects against measles, mumps, and rubella. Yet the United States and Europe have seen more than a few outbreaks of mumps, a contagious viral disease, in the past couple of years. The pattern of outbreaks of mumps suggests that the vaccine appears to be waning in its effectiveness. Researchers at Harvard believe that a single booster shot may help prevent future outbreaks.
Mumps is a very common viral infection that is spread through contact with mucus and saliva. It usually presents with a low-grade fever, loss of appetite, muscle ache and puffy cheeks as a result of swollen salivary glands. Most children with mumps do not get very sick and quickly get over the illness.
The Centers for Disease Control and Prevention recommended two doses of the mumps vaccine in childhood. This recommendation was made nearly early 40 years ago. For the most part, the vaccine has been very effective in preventing mumps in the majority of children.
However, the current outbreak is causing some concern to healthcare professional for two reasons. Firstly, there is a risk that nearly 10% of mumps infections may result in complications that include brain infection (meningitis), deafness or involvement of the ovaries or testes. Secondly, the most recent mumps outbreaks have been observed to occur in individuals who had already received the recommended two doses of vaccine as a child.
The question is: Is the vaccine less effective or are there new resistant strains of the mumps virus? Studies in the laboratory reveal that the mumps virus has not changed at all and thus the next logical conclusion is that the protection provided by the vaccine has diminished.
Follow up of individuals who had been vaccinated with the mumps vaccine indicate that its protection lasts about 27 years, and about 1/4th of these individuals will lose protection and be at risk for contracting mumps in 8 years; about 50% will be at risk in about 19 years, and 75% will be at risk in 38 years. In other words, with time, people start to lose protection against mumps.
The good news is that this protection can be established by a single booster shot at around age 18, but to date, no one knows how long the additional protection will last.