Photo by Dave Haygarth via Creative Commons
A very small number of people in a given population can forgo vaccines and still be protected from disease, thanks to the concept of herd immunity. But depending on the immunizations of others to prevent your child or yourself from getting sick may be contributing to the country’s unprecedented rates of measles infection.
“Parents who have refused to get their children vaccinated have put everyone who can’t get vaccinated at risk,” says Dr. Robert Belshe, professor of infectious diseases at Saint Louis University and founder of SLU’s Center for Vaccine Development. “This is easily preventable.”
In the city of St. Louis, according to a February 5 press release from the Health Department, the vaccination rate in schools is 92 to 95 percent. Only about three percent of families have opted out entirely of vaccination. Since 2005, the city has seen one reported case of the disease.
Some people can’t be vaccinated for medical reasons. For instance, babies under a year old still carry some antibodies from their mothers, Belshe says, which means that their bodies won’t respond to a vaccine by creating antibodies. While the maternal antibodies provide some protections, those infants are still at risk for the disease. People who are severely immunosuppressed because of other diseases can’t withstand vaccination either.
If everyone else gets vaccinated, those vulnerable populations are very unlikely to come in contact with the disease. But the pool must be kept very small, says Belshe: A susceptible population as small as 1 percent can enable transmission and cause the measles virus to spread.
The U.S. government declared measles eliminated from this country in 2000, but the disease has come roaring back. The highly contagious viral respiratory disease with the telltale rash had a record-breaking year in 2014, with 644 cases reported. According to CDC.gov, as of Jan. 30, there were 102 cases of measles reported in 14 states already in 2015—more than the entire year’s count for 2012. Most of those cases have been traced to the Disneyland theme parks in California.
The cause of the spike is straightforward—more people are choosing not to use the vaccine, according to Dr. Anne Schuchat, the assistant surgeon general for the United States Public Health Service and director of the Centers for Disease Control and Prevention’s National Center for Immunization and Respiratory Diseases. She said so at a CDC press briefing on Thursday, January 29.
People’s reasons to decide against vaccinations are myriad. A thoroughly discredited and retracted 1998 research paper by Andrew Wakefield, who was found guilty of serious professional misconduct for the paper and ultimately removed from medical practice altogether, put forth the incorrect theory that the vaccine is linked to autism. Belshe said some people still believe his thesis, though. Some parents decide against vaccinations for religious reasons, and some assume that herd immunity means their child doesn’t need a vaccine.
Whatever the reason, says Belshe, “They are going to put other people at risk. They are asking other people to bear the health costs of their decision.”
Tomorrow—a conversation with a St. Louis pediatrician who takes a novel approach when he’s talking to reluctant vaccinators.
