Vaccine effectiveness against medically attended, laboratory-confirmed influenza among children aged 6 to 59 months, 2003-2004
ABSTRACT Influenza is a leading cause of illness among children. Studies rarely have measured influenza vaccine effectiveness among young children, particularly when antigenic match between vaccine and circulating viruses is suboptimal. We assessed vaccine effectiveness against medically attended, laboratory-confirmed influenza for children who were aged 6 to 59 months during the 2003-2004 influenza season.
In a case-control study that was conducted in a single pediatric practice, case patients who were aged 6 to 59 months and had laboratory-confirmed influenza were age matched 1:2 to eligible control subjects. Vaccination status was ascertained as of the date of the case patient's symptom onset. Conditional logistic regression was used to calculate vaccine effectiveness, adjusting for underlying medical conditions and health care usage.
We identified 290 influenza case patients who were seen for medical care from November 1, 2003, to January 31, 2004. Vaccine effectiveness among fully vaccinated children, compared with unvaccinated children, was 49%. Partially vaccinated children who were aged 6 to 23 months had no significant reduction in influenza (vaccine effectiveness: -70%), but partially vaccinated children who were aged 24 to 59 months had a significant (65%) reduction in influenza, compared with unvaccinated children.
Full vaccination provided measurable protection against laboratory-confirmed influenza among children who were aged 6 to 59 months during a season with suboptimal vaccine match. No vaccine effectiveness was identified with partial vaccination among children who were aged 6 to 23 months, affirming that children need to be fully vaccinated to obtain protective effects. These results strengthen the evidence of the vaccine's ability to reduce substantially the burden of disease in this age group.
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- "However, the majority of these studies were conducted among children. In children less than 5 years of age and asthmatic children 6–17 years of age, LAIV was found to have superior efficacy and effectiveness in comparison to TIV    . A limited number of studies, mostly randomized trials or experimental challenge studies, have been conducted among adults. "
ABSTRACT: Limited effectiveness data are available comparing live attenuated influenza vaccine (LAIV) to inactivated influenza vaccine (TIV) among adults. To compare the incidence of influenza-like illness following immunization of adults with LAIV vs. TIV, we conducted a retrospective cohort analysis of active component U.S. military personnel for the 2005-2006 and 2006-2007 influenza seasons. Recruits experienced a much higher burden of disease compared to non-recruits, with crude incidence rates of influenza-like illness 2-16 times higher than non-recruits depending on the season and cohort. For both seasons, a slightly greater protection from influenza-like illness was found for non-recruits who received TIV compared to LAIV (adjusted incidence rate ratio, 1.17 (95% CI, 1.14-1.20) and 1.33 (95% CI, 1.30-1.36), 2005-2006 and 2006-2007 influenza seasons, respectively). However, for Army and Air Force recruits, LAIV was found to provide significantly greater protection from influenza-like illnesses compared to TIV, with adjusted incidence rates of influenza-like illness 22-51% and 18-47% lower among LAIV compared to TIV recipients for the 2005-2006 and 2006-2007 influenza seasons, respectively. Possible reasons for differences in recruit and non-recruit findings include differences in pre-existing influenza antibody levels, differing respiratory disease burden, and/or unmeasured confounding. Consideration of these findings should be made when developing influenza immunization policies.Vaccine 07/2009; 27(27):3568-75. DOI:10.1016/j.vaccine.2009.03.088