June 27, 2016
In a recent study published in the journal Vaccine, researchers from the University of Missouri had hypothesized that directing people to information on vaccine side effect reports would reassure people that reported side effects are rare and may have nothing to do with vaccination at all. This would then make people more likely to get the vaccine in question.
“One of the issues in vaccine acceptance is trust,” researcher Laura Scherer said. “Individuals, parents and vaccine opponents lack trust that doctors and the government have done sufficient research to validate the safety of vaccines. By educating participants about the VAERS system, we thought that this might increase trust that the Centers for Disease Control [and Prevention (CDC)] are doing everything that they can to research and document vaccine harms.”
Instead, the researchers found that letting people read the side effect reports made them less trustful of vaccines and the CDC, and less likely to get vaccinated.
Are more informed patients less likely to vaccinate?
The study was conducted on more than 1,200 people who were eligible to receive the Human Papillomavirus (HPV) vaccine. One-third of the participants were provided with the standard vaccine statement that all patients are supposed to receive before getting the HPV shot. Another third were provided with the vaccine statement, plus information on the Vaccine Adverse Event Reporting System (VAERS) and a summary showing that in 2013, there were 31 serious adverse events reported among 10 million HPV vaccinations: 24 reports of disability and 7 reports of death. The final third received everything the second group received, plus detailed accounts of the 31 cases.
The VAERS is a safety reporting system developed by the CDC. It allows anyone to report any adverse event that happens following a vaccination, without needing to prove that the vaccine caused the effect. The database is available online for anyone to view.
“Since anyone can report anything to VAERS for any reason, the VAERS reports contain incidents of serious adverse events that may not have anything to do with the vaccine,” Scherer said. “We thought that by having people read the actual reports, they would see that there are very few reported serious events, and that the vaccine may not have even caused the event. Taken together, we felt this might make participants feel more assured that vaccines are safe—but in fact, what we found was the opposite.”
Participants who received the VAERS report summary reported being slightly more likely to get the HPV vaccine than those who only received the vaccine statement. But participants who read the adverse event reports were less likely to vaccinate, and reported decreased trust in CDC promises of vaccine safety.
Mistrust in health agencies fuels vaccine refusal
Notably, vaccine mistrust increased even among participants who didn’t think the HPV vaccine had even caused the adverse events they read about.
“When participants read the incident reports, there was a marked reduction in their willingness to vaccinate—even though most participants believed the vaccines caused few or even none of the deaths,” Scherer said. “Stories about vaccine harms can influence vaccine acceptance even when people don’t completely believe them.”
The findings build on prior research showing that people become less likely to vaccinate when they think public health agencies are exaggerating the safety of vaccines. A 2014 study in the Journal of Risk Research found that during Israel’s 2013 polio outbreak, many parents who normally complied with all vaccine recommendations refused to give their children the extra course of polio vaccine recommended by the government.
The most common reasons cited for refusal were concerns about vaccine safety and a feeling that the government had not really explained the need for the extra vaccine. Parents were particularly turned off by assurances that there were “zero side effects,” interpreting such blanket statements as patently false and condescending.
Sources for this article include: