David Ojcius and Paul Brown: Vaccination against measles protects entire community
Measles was considered eradicated in the U.S. in 2000. But as of this month, nearly 200 cases have already been reported in the U.S., and a child in Merced County was one of the most recent victims (“Merced County child found to have measles,” March 4, Page A1).
The number of measles cases is increasing nationwide, with unproven fears that the MMR (measles, mumps, rubella) vaccine may cause autism being partly to blame.
The measles virus can linger in water droplets in the air for up to two hours, and small babies are especially vulnerable since they lack a mature immune system and are too young to receive the vaccine. While few parents in the U.S. choose to skip the vaccination for their children, communities with high opt-out rates are scattered throughout the country. Most of the recent cases have occurred in people who were not vaccinated against the measles virus.
In some ways, becoming vaccinated against measles is a social obligation as much as an individual choice. By becoming vaccinated, we protect our community. Vaccinated people are less likely to contract measles than unvaccinated people, so they decrease transmission of the virus to both vaccinated and unvaccinated community members.
In other words, the chain of infection is disrupted when a large percentage of the community is immune to measles. The larger the number of community members who are resistant, the lower the chance that a susceptible (unvaccinated) person will come into contact with an infectious person and, in turn, become infected. This phenomenon is known as “herd immunity”.
As becomes obvious from the current outbreak, measles is a highly transmissible infection. This high rate of transmission means that more than 90 percent of the population must be vaccinated in order to protect the entire community through “herd immunity.”
The sad truth about the current outbreak is that as long as many members of our community have strong negative views about vaccination, we will continue to have outbreaks of vaccine-preventable diseases such as measles.
We believe we should strive for the goal of vaccinating 100 percent of the population. Every member of the community who can be vaccinated should receive the vaccine, to protect both himself or herself and our neighbors who cannot be vaccinated for medical reasons – because they are too young or have other medical conditions that prevent them from benefiting from vaccination. Nobody should opt-out for personal or religious reasons.
We should also try to respect concerns about vaccination, and try to understand the source of those concerns if we are to address them successfully.
Ojcius is a professor of immunology and Brown is a professor of public health at the Health Sciences Research Institute, UC Merced.
More on measles
▪ So far this year, 170 people in 17 states have been sickened with measles, according to the Centers for Disease Control and Prevention. The initial outbreak started in Disneyland at the end of December.
▪ The measles rash typically appears first on the face, along the hairline, and behind the ears and then affects the rest of the body. Infected people are usually contagious from about four days before their rash starts to four days afterward, according to the California Department of Public Health.
▪ Measles can be prevented with the MMR (measles, mumps, rubella) vaccine. One MMR vaccine is about 93 percent effective at preventing measles if exposed; two doses (recommended) are about 97 percent effective, according to the CDC. High school students who have not been previously vaccinated need two doses separated by at least 28 days.
▪ Many studies have investigated a link between the measles vaccine and autism spectrum disorders; absolutely no link has been found.
This story was originally published March 10, 2015 at 11:04 AM with the headline "David Ojcius and Paul Brown: Vaccination against measles protects entire community."