But things aren’t so simple. In fact, the conflicting evidence about the live nasal flu vaccine offers an excellent case study on how complex the task of analyzing flu vaccine data and making recommendations really is.
“Sometimes the public wants a very simple message, and unfortunately life’s not like that,” Mark Loeb, the new study’s lead author and director of the division of infectious diseases at McMaster University in Ontario, tells Shots. “Things change as the evidence grows and we understand more. Unfortunately, that’s how science and clinical medicine work. The challenge is to be able to help the public understand the shades of gray here.”
Loeb’s study focused on 52 Hutterite communities in rural Canada, because their relative isolation makes for an environment with fewer confounding factors. Researchers randomly assigned 1,186 children, ages 3 to 15, to receive either the live attenuated nasal flu vaccine or the inactivated flu vaccine by injection.
During the three flu seasons from 2012 to 2015, 5.3 percent of the children in the live nasal vaccine group and 5.2 percent of the children in the inactivated vaccine group had lab-confirmed influenza, revealing that the two vaccines were equally effective.
The study lacked a control group of children who did not get a vaccine, but previous studies showed a flu infection rate of about 10 percent among unvaccinated children and of 4 to 5 percent in vaccinated children in these communities, Loeb says. Rates of antibiotic prescriptions, ER visits, respiratory illnesses, hospital admissions and school or work absences were also similar across the two groups.
These findings, published Monday in Annals of Internal Medicine, parallel the early evidence …