Hamilton, Ontario—Less than 2 months after an advisory committee of the CDC recommended against use of live attenuated influenza vaccine (LAIV) during the 2016-2017 influenza season, a Canadian study reports that LAIV, delivered as a nasal spray, works as well as a standard flu shot.
Results of the study, conducted in relatively isolated Hutterite communities in Alberta and Saskatchewan, were published recently in Annals of Internal Medicine.
The McMaster University–led research finds that while LAIV did not provide better direct or community protection against influenza than the inactivated influenza vaccine, protection was similar in both groups. Earlier studies conducted in young children had suggested that the nasal spray vaccine provided better direct protection against flu than the standard shot, leading to improved herd immunity, as well.
“Our results are important because in previous years the live vaccine had first been preferred for children. In fact, as late as June 2014, the live vaccine was preferred,” explained lead author Mark Loeb, MD, MSc. “Then, subsequently, it was no longer preferred and now not recommended at all. Our trial showed no difference between the two in protecting entire communities.”
For the cluster randomized trial, researchers focused on Hutterite colonies where residents live communally and are relatively isolated from cities and towns to determine whether vaccinating children and adolescents with LAIV provided better direct and community protection than the inactivated version in a shot. With 1,186 children in 52 such communities receiving the nasal spray vaccine, another 3,425 children were randomized to receive the standard flu shot.
Results indicate that average vaccine coverage among children in the nasal spray group was 76.9% versus 72.3% in the flu shot group.
The original intention of the study was to show that nasal spray vaccines would provide better protection than flu shots, Loeb explained in a McMaster University press release, but suggests the study conclusions are now especially important, given the recommendations from the CDC’s Advisory Committee on Immunization Practices (ACIP), which were based on recent studies indicating very low effectiveness.
“The ACIP's decision was an unprecedented decision in influenza vaccine policy-making for children,” he emphasized. “Our study challenges previous studies because our results show conclusively that the vaccines show similar protection when both direct and indirect effects are taken into account.”
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