A new study examines whether a vaccine that offers only partial protection can backfire by increasing risky behavior, as a false sense of security could make recipients less careful than they otherwise would be.
While the study looks at the response to Lyme disease vaccination, its authors suggest the research also sheds light on the controversy over whether girls should receive the HPV vaccine to fight cervical cancer.
Ticks spread Lyme disease, which is usually treatable by antibiotics. However, late detection or a poor response to antibiotics can lead to lasting pain, fatigue and neurological problems. The vaccine, known is LYMErix, is about 80 percent effective.
Noel Brewer, Ph.D., assistant professor of public health at the University of North Carolina, is lead author of the study, which appears online and in the August print issue of the Annals of Behavioral Medicine .
Brewer and colleagues conducted a random phone survey of 705 adults, who lived in areas where Lyme disease is common, just after the vaccine became available. Eighteen months later, they re-interviewed participants and compared the behavior of those who received the vaccination to those who had not.
The researchers looked for evidence of “risk compensation”— a phenomenon in which people maintain a relatively stable level of risk-taking. For example, some studies find that people “compensate” for risk reduction caused by seatbelt use by driving faster.
“When you talk about risk compensation, there are two things that could happen,” Brewer said. Vaccinated individuals might reduce other efforts to avoid Lyme; for example, they might stop wearing light-colored clothing that makes ticks visible. If they reduced this behavior only to the level of unvaccinated individuals, their risk would stay the same. Brewer calls this “regression.”
Alternatively, people might become “disinhibited” by vaccination and less cautious than the unvaccinated, in which case vaccination might actually increase their risk because it is not 100 percent effective.
In the study, the authors found evidence of regression on two safety measures: wearing light-colored clothing and using tick repellant. However, they found no evidence of disinhibition, which led Brewer to conclude that fears of disinhibition related to the HPV vaccine could be overblown as well.