Most vaccines protect us in two ways. They provide individual protection to the vaccinated person and each vaccinated person who is protected (immune) contributes to the immunity of the population as a whole. This is called “herd” immunity. Since 2000, measles herd immunity has been so good in the United States that the measles virus no longer circulates. The recently reported cases of measles in the United States have been the result of importations from other countries with limited secondary transmission to non-immune Americans.
The vaccine contrarian Bob Sears recently asked what the big deal is about seven cases (“not 700” cases) of measles in Orange County. In addition to the fact that measles can be quite severe and is vaccine-preventable, there is a bigger public health problem. Specifically, public health staff in each state must identify and check all the contacts of each case in an attempt to prevent additional cases of disease. Since the number of contacts is often sizable, this is an extremely time consuming and costly process. In California this year, there have been 56 cases of measles. For each case, there may be hundreds of exposed persons who need to be investigated by public health; one case this year in Orange County had over 1,000 contacts. Depending on their immune status and overall health, exposed persons may need to receive preventive immunization or immune globulin after exposure.
As it turns out, a significant number of exposed persons have medical conditions which have precluded them from immunization or otherwise make them at an increased risk for severe and fatal measles. For example, an exposed child who is being treated for leukemia will need to be treated prophylactically with intravenous immune globulin that will cost thousands of dollars. Other exposed persons will need to be vaccinated immediately or given intramuscular immune globulin. This all takes considerable time and is expensive. Furthermore, decisions about which exposed persons are at risk of severe measles infection and need IVIG often require consultation with medical specialists, and decisions need to be made in hours not days, because these interventions are only effective if done in a timely way.
It is concerning that there have been so many imported measles cases and so much secondary transmission of measles in the United States in 2014. Increasing numbers of unimmunized children may decrease herd immunity below protective levels. If this happens, measles could again begin to circulate in the United States. As the number of measles cases increases, the risk that there will be cases that result in death or brain damage also increases. Lifesaving treatments, such as bone marrow transplantation, that weren’t available in the pre-vaccine era, have increased the number of immunocompromised people in the population, but even previously healthy persons can develop complications from measles infection. In addition, the costs to public health departments of tracing measles contacts and seeing that they get appropriate prophylaxis runs into many thousands of dollars.
In 2014, a new law on exemptions from California school and childcare immunization requirements became effective in California. The intent of this law was to ensure that parents wishing to exempt their children from required immunizations received information about the benefits and risks of immunizations and the risks of vaccine-preventable diseases from a health care practitioner prior to obtaining an exemption. Under the previous law, parents needed only to sign a form to exempt their child from the requirements. However, when Governor Brown signed the bill into law he required that there be a religious exemption, which was not in the previous law. Parents who use this provision do not need to receive information from a health care provider, which essentially negated the intent of the law. In addition, naturopathic doctors were added to the list of health care practitioners who could provide information to parents. (This is like having the fox guard the chicken coop).
Yes, Bob Sears, measles is a big deal in 2014. Parents, doctors, and other health care personnel should ensure that all children without medical contraindications receive two doses of MMR (measles, mumps, and rubella) vaccine.