Quadrivalent Influenza Vaccine Found to be Safe

FluMist, QLAIV, quadrivalent live attenuated influenza vaccine
FluMist, QLAIV, quadrivalent live attenuated influenza vaccine
No safety signals associated with the administration of quadrivalent live attenuated influenza vaccine were observed, according to a large population study.

No clinically meaningful safety signals were observed in association with the administration of the quadrivalent live attenuated influenza vaccine (Q/LAIV), according to results of a large population study published in Vaccine.

In a prospective, nonrandomized, observational cohort study (ClinicalTrials.gov identifier: NCT01985997), data from the Kaiser Permanente Northern California (KPNC) health plan were analyzed from 62,040 Q/LAIV (FluMist®, MedImmune, Gaithersburg, MD) recipients aged 2 to 49 years during the 2013 to 2014 influenza season.

Roger Baxter, MD, co-director of the Kaiser Permanente Vaccine Study Center in Oakland, California, and colleagues compared rates of medically attended events and hospitalization immediately after Q/LAIV vaccination with rates observed during the reference periods later in the follow-up period (within-cohort analysis).  Rates were also compared with 2 frequency-matched groups: inactivated influenza vaccine (IIV) recipients and unvaccinated controls.

Of the 62,040 Q/LAIV recipients, 88% (n=54,647) were aged 2 to 17 years, including 29,992 children between the ages of 2 and 8 years. Within 42 days following vaccination, lower respiratory tract infections (n=157) and wheezing (n=121) were the most frequent incident events in Q/LAIV recipients. During this period, 41 Q/LAIV recipients were hospitalized, 3 of which were hospitalized for respiratory disease. During the risk interval (days 0 to 3), 14 Q/LAIV recipients were diagnosed with hypersensitivity; seizures and convulsions were not observed during this time.

When compared by age group, Q/LAIV recipients aged 5 to 8 years had a significantly higher risk of hypersensitivity during the risk interval (days 0 to 3) vs the reference period (days 7 to 9; 5 vs 0 cases, P =.05); however, no one was seen in an emergency department or admitted to a hospital. This observation was limited to children attending/visiting physician clinics.

Compared with unvaccinated controls by age group (n=44), Q/LAIV recipients 2 to 4 years of age (n=66) were at higher risk of wheezing (adjusted hazard ratio [HR] 1.50; 95% CI, 1.03-2.20). Within this group, 4 Q/LAIV recipients and 5 unvaccinated controls required treatment in the emergency department; none were hospitalized. Again, this observation was limited to children attending/visiting physician clinics.

No significant risk was observed between Q/LAIV and IIV recipients in any setting, including analyses by age group. However, a complementary analysis conducted among children between the ages of 2 and 4 years with a history of wheezing or asthma showed that the risk of wheezing after vaccine administration was lower among Q/LAIV recipients (HR 0.21; 95% CI, 0.01-1.22) than among IIV recipients (HR 0.51; 95% CI, 0.02-4.79).

No safety signals were observed with the administration of Q/LAIV. “These results are consistent with those of other pre-approval and post-licensure clinical studies that have demonstrated the safety of Q/LAIV among eligible children, adolescents, and adults,” concluded the researchers.


Co-authors Herve Caspard and Christopher S. Ambrose are full-time employees of AstraZeneca. This study was sponsored by MedImmune, the global biologics research and development arm of AstraZeneca. MedImmune/AstraZeneca participated in the study design, review, and interpretation of study data, and development of the manuscript.

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Baxter R, Eaton A, Hansen J, Aukes L, Caspard H, Ambrose CS. Safety of quadrivalent live attenuated influenza vaccine in subjects aged 2-49 years. Vaccine. 2017;35:1254-1258. doi: 10.1016/j.vaccine.2017.01.062