Residents of Many States are Inadequately Vaccinated Against Measles, Expert Says

February 12, 2019

As several reports emerge highlighting measles outbreaks across the country, Virginia Tech infectious disease expert Kate Langwig points out that inadequate vaccine coverage in states like Washington may help explain the trend.

According to Langwig, an assistant professor in the Department of Biological Sciences in the College of Science,“For populations to be fully protected against measles, 91 to 95 percent or more of the population needs to be vaccinated. A recent CDC report showed that Washington state had one of the lowest MMR vaccine coverage rates in the nation among children under 3, at 88.5 percent.”

The CDC report shows that many states do not meet the 91 percent to 95 percent threshold Langwig recommends.

Another concern Langwig notes is, "Babies do not get the measles vaccine until they are 9 to 15 months old, with the second vaccine dose at 4 to 6 years, so the very young can be inadequately protected even if they are following recommended guidelines for vaccination. This makes it more critical that people that can be vaccinated comply with CDC vaccination recommendations because by getting a vaccine yourself, you are helping to stop the spread of viruses and prevent them from being transmitted to children that aren’t yet vaccinated. ”

Langwig continues, "For many infectious diseases, we rely on herd immunity to prevent outbreaks of vaccine-preventable infections. Herd immunity is the protection of the 'herd,' our population, by preventing infections in the vast majority people. We can calculate the percentage of the population that needs to be vaccinated to prevent diseases from spreading, and maintain herd immunity. For some pathogens, like measles, the number that needs to vaccinated is very high because the measles virus spreads so easily. There is some evidence to suggest that vaccination rates are dropping in some states that don't require vaccination, and parents that opt out of vaccines are doing so for reasons that don't reflect our current state of knowledge of vaccine safety. Increases in vaccine-preventable infections may lead to a larger number of states enacting laws that restrict religious and personal belief exemptions for vaccination. California did this in 2015 after serious outbreaks of measles in Disneyland. Hopefully, laws like that will help to reduce measles outbreaks although education is also likely to be a key factor in improving vaccine uptake.”

Langwig's research focuses on the ecology and evolution of infectious diseases, pathogen transmission, impacts of pathogens on ecological communities, and the conservation and policy implications of infectious disease.

Source: Virginia Tech