The study led by McMaster University researchers has found that, contrary to recent reports, flu nasal sprays provide similar protection against influenza as standard flu shots. The study shows that the nose spray had a similar effect to the standard flu shot. Previous recommendations from the Centres for Disease Control and Prevention’s Advisory Committee on Immunization Practices (ACIP) had previously called for nasal sprays, or live attenuated influenza vaccine (LAIV), not be used during the 2016-2017 flu season.
Dr Mark Loeb, lead author of the study, says his team’s findings challenge the ACIP’s recommendations towards flu shots, or inactivated vaccines. “Our study is the first blinded randomised controlled trial to compare the direct and indirect effect of the live vaccine versus the inactivated vaccine,” said Loeb, a professor in McMaster’s department of pathology and molecular medicine.
“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. 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 study, Loeb’s team conducted a three-year trial in a Hutterite colony, where people live communally and are relatively isolated from cities and towns, to determine whether vaccinating children and adolescents with the flu nasal spray provided better direct and community protection than the standard flu shot.
The researchers randomly assigned 1,186 children in 52 Hutterite colonies in Alberta and Saskatchewan, Canada to receive either the nasal spray vaccine or the flu shot and also followed 3,425 community members who did not receive a flu vaccine.
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, but Loeb says the conclusions of the study are now especially important, given the ACIP’s recommendations.
“The ACIP’s decision was an unprecedented decision in influenza vaccine policy-making for children. 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.”
Loeb says his team will continue to study herd immunity with different vaccine formulations by vaccinating children. They are also looking at the effect of repeated vaccination of children.
Background: Whether vaccinating children with intranasal live attenuated influenza vaccine (LAIV) is more effective than inactivated influenza vaccine (IIV) in providing both direct protection in vaccinated persons and herd protection in unvaccinated persons is uncertain. Hutterite colonies, where members live in close-knit, small rural communities in which influenza virus infection regularly occurs, offer an opportunity to address this question.
Objective: To determine whether vaccinating children and adolescents with LAIV provides better community protection than IIV.
Design: A cluster randomized blinded trial conducted between October 2012 and May 2015 over 3 influenza seasons.
Setting: 52 Hutterite colonies in Alberta and Saskatchewan, Canada.
Participants: 1186 Canadian children and adolescents aged 36 months to 15 years who received the study vaccine and 3425 community members who did not.
Intervention: Children were randomly assigned according to community in a blinded manner to receive standard dosing of either trivalent LAIV or trivalent IIV.
Measurements: The primary outcome was reverse transcriptase polymerase chain reaction–confirmed influenza A or B virus in all participants (vaccinated children and persons who did not receive the study vaccine).
Results: Mean vaccine coverage among children in the LAIV group was 76.9% versus 72.3% in the IIV group. Influenza virus infection occurred at a rate of 5.3% (295 of 5560 person-years) in the LAIV group versus 5.2% (304 of 5810 person-years) in the IIV group. The hazard ratio comparing LAIV with IIV for influenza A or B virus was 1.03 (95% CI, 0.85 to 1.24).
Limitation: The study was conducted in Hutterite communities, which may limit generalizability.
Conclusion: Immunizing children with LAIV does not provide better community protection against influenza than IIV.
Mark Loeb; Margaret L Russell; Vanessa Manning; Kevin Fonseca; David JD Earn; Gregory Horsman; Khami Chokani; Mark Vooght; Lorne Babiuk; Lisa Schwartz; Binod Neupane; Pardeep Singh; Stephen D Walter; Eleanor Pullenayegum