Measles is a highly contagious disease that can lead to pneumonia, encephalitis, hospitalization and, occasionally, death. Currently, significant numbers of children in the US are at risk from this disease, due to gaps in measles vaccination rates, according to an analysis of national vaccination coverage presented at IDWeek 2015.
People who are not vaccinated, or who have received only one dose, run a high risk of disease, because measles can easily be caught through direct contact and droplets that spread through the air.
Measles is one of the most contagious of the vaccine-preventable diseases. This means that to stop it from being transmitted, the highest levels of immunity must be maintained.
Normally, the measles, mumps and rubella (MMR) vaccine, containing a weakened live virus, is given to children in two doses, the first at 12-15 months and the second at 4-6 years of age. All children are required to receive the two doses of the MMR vaccine before starting school.
However, since the virus is not recommended for those with a weakened immune system, children with medical issues, such as an immune disorder or cancer, are exempt.
- From January 1st-September 18th this year, 189 people from 24 states plus DC had measles
- 62% of these were linked to an amusement park in California
- 2014 saw a record number of 668 cases in the US.
Other exemptions have been granted for personal or religious reasons, although three states are no longer allowing this, the latest being California.
In some places, lack of access or awareness of the need for vaccines can mean that a child is not immunized.
Currently, measles is not widespread because the majority of people have been vaccinated, which minimizes the number of people vulnerable to infection and helps protect those who cannot be vaccinated by preventing their exposure to the virus.
However, researchers from Emory University have found that 92-94% of children are immune to measles, which is significant because below this threshold, measles outbreaks are possible and could lead to widespread illness.
In an analysis of the National Immunization Survey-Teen, researchers found that nearly 1 in 4 children aged under 3 years are at risk, and 4.6% of those aged 17 had not received any doses of the vaccine.
The team determined that 12.5% of all children – or 8.7 million – were not fully protected by vaccination and therefore were susceptible to measles; 24.7% of children under 3 are particularly at risk, as they are too young to be fully vaccinated.
If the percentage of vaccinated children drops to just 98% of current levels, it is estimated that 14.2% of children – or 1 in 7 – would be vulnerable to measles.
Dr. Robert Bednarczyk, PhD – lead author of the study and assistant professor in the Hubert Department of Global Health, Rollins School of Public Health at Emory University in Atlanta, GA – says:
“Although we eliminated continuous measles transmission in the United States about 15 years ago thanks to the effectiveness of the MMR vaccine and robust vaccination rates, these study results show that we can’t get complacent. While we currently have overall immunity in the population that should prevent sustained measles transmission, if the virus is introduced, there is the potential for large outbreaks. This is because there are clusters of unvaccinated children in some communities, which could allow a large outbreak to occur with spread to similar communities.”
Dr. Bednarczyk adds that doctors need to ensure that those who received only one dose receive a second dose at the recommended age.
He calls on parents to ensure that their children are vaccinated, emphasizing that the vaccine is “very safe,” while not vaccinating is “highly risky” and will expose their children and others around to a serious illness entailing a number of complications.
At the moment, he says “these children are protected because of the high vaccine coverage of the population, but that will change if we begin having more outbreaks and the percentage of children vaccinated declines.”
Medical News Today reported earlier this year on the concern over under-vaccination and recent measles outbreaks.