Adverse Events After Receipt of Live, Attenuated Influenza Vaccine (LAIV)

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Children
Adults
Persons at Higher Risk from Influenza-related Complications
Serious Adverse Events

Children

In a subset of healthy children aged 60--71 months from one clinical trial, certain signs and symptoms were reported more often after the first dose among LAIV recipients (n = 214) than among placebo recipients (n = 95), including runny nose (48% and 44%, respectively); headache (18% and 12%, respectively); vomiting (5% and 3%, respectively); and myalgias (6% and 4%, respectively). However, these differences were not statistically significant. In other trials, signs and symptoms reported after LAIV administration have included runny nose or nasal congestion (20%--75%), headache (2%--46%), fever (0--26%), vomiting (3%--13%), abdominal pain (2%), and myalgias (0--21%). These symptoms were associated more often with the first dose and were self-limited.

In a randomized trial published in 2007, LAIV and TIV were compared among children aged 6--59 months. Children with medically diagnosed or treated wheezing within 42 days before enrollment, or a history of severe asthma, were excluded from this study. Among children aged 24--59 months who received LAIV, the rate of medically significant wheezing, using a pre-specified definition, was not greater compared with those who received TIV; wheezing was observed more frequently among younger LAIV recipients in this study (see Persons at Higher Risk from Influenza-Related Complications). In a previous randomized placebo-controlled safety trial among children aged 12 months--17 years without a history of asthma by parental report, an elevated risk for asthma events (RR = 4.06, CI = 1.29--17.86) was documented among 728 children aged 18--35 months who received LAIV. Of the 16 children with asthma-related events in this study, seven had a history of asthma on the basis of subsequent medical record review. None required hospitalization, and elevated risks for asthma were not observed in other age groups.

Another study was conducted among >11,000 children aged 18 months--18 years in which 18,780 doses of vaccine were administered for 4 years. For children aged 18 months--4 years, no increase was reported in asthma visits 0--15 days after vaccination compared with the prevaccination period. A significant increase in asthma events was reported 15--42 days after vaccination, but only in vaccine year 1.

Initial data from VAERS during 2007--2008, following ACIP recommendation for LAIV use in children aged 2--4 years, do not suggest a concern for wheezing after LAIV in young children. However data also suggest uptake of LAIV is limited and continued safety monitoring for wheezing events after LAIV is indicated (CDC, unpublished data, 2008).

Adults

Among adults, runny nose or nasal congestion (28%--78%), headache (16%--44%), and sore throat (15%--27%) have been reported more often among vaccine recipients than placebo recipients. In one clinical trial among a subset of healthy adults aged 18--49 years, signs and symptoms reported more frequently among LAIV recipients (n = 2,548) than placebo recipients (n = 1,290) within 7 days after each dose included cough (14% and 11%, respectively); runny nose (45% and 27%, respectively); sore throat (28% and 17%, respectively); chills (9% and 6%, respectively); and tiredness/weakness (26% and 22%, respectively).

Persons at Higher Risk from Influenza-related Complications

Limited data assessing the safety of LAIV use for certain groups at higher risk for influenza-related complications are available. In one study of 54 HIV-infected persons aged 18--58 years and with CD4 counts 200 cells/mm3 or greater who received LAIV, no serious adverse events were reported during a 1-month follow-up period. Similarly, one study demonstrated no significant difference in the frequency of adverse events or viral shedding among HIV-infected children aged 1--8 years on effective antiretroviral therapy who were administered LAIV, compared with HIV-uninfected children receiving LAIV. LAIV was well-tolerated among adults aged 65 years and older with chronic medical conditions. These findings suggest that persons at risk for influenza complications who have inadvertent exposure to LAIV would not have significant adverse events or prolonged viral shedding and that persons who have contact with persons at higher risk for influenza-related complications may receive LAIV.

Serious Adverse Events

Serious adverse events after administration of LAIV requiring medical attention among healthy children aged 5--17 years or healthy adults aged 18--49 years occurred at a rate of <1%. Surveillance will continue for adverse events, including those that might not have been detected in previous studies. Reviews of reports to VAERS after vaccination of approximately 2.5 million persons during the 2003--04 and 2004--05 influenza seasons did not indicate any new safety concerns. Health-care professionals should report all clinically significant adverse events occurring after LAIV administration promptly to VAERS after LAIV administration.

NOTE: The text above is taken from Prevention & Control of Influenza - Recommendations of the Advisory Committee on Immunization Practices (ACIP) 2008. MMWR 2008 Jul 17; Early Release:1-60. (Also available as PDF, 586K).