Efficacy of trivalent influenza vaccine against laboratory-confirmed influenza among young children in a randomized trial in Bangladesh.

BACKGROUND: Few trials have evaluated influenza vaccine efficacy (VE) in young children, a group particularly vulnerable to influenza complications. We aimed to estimate VE against influenza in children aged <2 years in Bangladesh; a subtropical setting, where influenza circulation can be irregular. METHODS: Children aged 6-23 months were enrolled 1:1 in a parallel, double-blind, randomized controlled trial of trivalent inactivated influenza vaccine (IIV3) versus inactivated polio vaccine (IPV); conducted August 2010-March 2014 in Dhaka, Bangladesh. Children received two pediatric doses of vaccine, one month apart, and were followed for one year for febrile and respiratory illness. Field assistants conducted weekly home-based, active surveillance and ill children were referred to the study clinic for clinical evaluation and nasopharyngeal wash specimen collection. Analysis included all children who received a first vaccine dose and compared yearly incidence of reverse transcription polymerase chain reaction (RT-PCR)-confirmed influenza between trial arms. The VE was estimated as 1-(rate ratio of illness) × 100%, using unadjusted Poisson regression. The trial was registered with ClinicalTrials.gov, number NCT01319955. RESULTS: Across four vaccination rounds, 4081 children were enrolled and randomized, contributing 2576 child-years of observation to the IIV3 arm and 2593 child-years to the IPV arm. Influenza incidence was 10 episodes/100 child-years in the IIV3 arm and 15 episodes/100 child-years in the IPV arm. Overall, the VE was 31% (95% confidence interval 18, 42%) against any RT-PCR-confirmed influenza. The VE varied by season, but was similar by influenza type/subtype and participant age and sex. CONCLUSIONS: Vaccination of young children with IIV3 provided a significant reduction in laboratory-confirmed influenza; however, exploration of additional influenza vaccine strategies, such as adjuvanted vaccines or standard adult vaccine doses, is warranted to find more effective influenza vaccines for young children in low-income countries.

Influenza Among Young Children in Bangladesh: Clinical Characteristics and Outcomes From a Randomized Clinical Trial.

BACKGROUND: Influenza causes substantial morbidity in children worldwide, although influenza vaccine is seldom used in low-resource settings. More information on the clinical presentation of influenza and the efficacy of vaccine is needed to inform policy. METHODS: In 2013 we conducted a randomized, placebo-controlled clinical trial of live attenuated influenza vaccine (LAIV) in children aged 24-59 months in Bangladesh (N = 1761). If participants met prespecified specimen collection criteria, we collected nasopharyngeal washes for testing by singleplex reverse-transcription polymerase chain reaction (RT-PCR) for laboratory-confirmed influenza virus infection (LCI). A panel of RT-PCR assays was used to detect noninfluenza respiratory viruses. Primary efficacy results have been reported. In this analysis of prespecified and post hoc objectives from the trial, we compared signs and symptoms between LCI and non-LCI cases and estimated the efficacy of LAIV against moderate-to-severe LCI and other prespecified non-LCI clinical outcomes including all-cause pneumonia and acute otitis media. RESULTS: The most common signs and symptoms of LCI were fever, cough, and runny nose. The combination of subjective fever and cough had a 63% sensitivity for LCI. The combination of measured fever, cough, and runny nose was most specific (90%) but had low sensitivity (32%) for LCI. The efficacy of LAIV against vaccine-strain moderate-to-severe LCI was 56.7% (95% confidence interval, 9.5%-79.2%). No statistically significant vaccine efficacy was found against the non-laboratory-confirmed clinical outcomes. CONCLUSIONS: It was not possible to distinguish LCI from noninfluenza viral infections on clinical evaluations alone in this population of Bangladeshi children. LAIV was efficacious against moderate-to-severe LCI. CLINICAL TRIALS REGISTRATION: NCT01797029.

Efficacy of a Russian-backbone live attenuated influenza vaccine among young children in Bangladesh: a randomised, double-blind, placebo-controlled trial.

BACKGROUND: The rates of influenza illness and associated complications are high among children in Bangladesh. We assessed the clinical efficacy and safety of a Russian-backbone live attenuated influenza vaccine (LAIV) at two field sites in Bangladesh. METHODS: Between Feb 27 and April 9, 2013, children aged 2-4 years in urban Kamalapur and rural Matlab, Bangladesh, were randomly assigned in a 2:1 ratio, according to a computer-generated schedule, to receive one intranasal dose of LAIV or placebo. After vaccination, we monitored children in weekly home visits until Dec 31, 2013, with study clinic surveillance for influenza illness. The primary outcome was symptomatic, laboratory-confirmed influenza illness due to vaccine-matched strains. Analysis was per protocol. The trial is registered with ClinicalTrials.gov, number NCT01797029. FINDINGS: Of 1761 children enrolled, 1174 received LAIV and 587 received placebo. Laboratory-confirmed influenza illness due to vaccine-matched strains was seen in 93 (15·8%) children in the placebo group and 79 (6·7%) in the LAIV group. Vaccine efficacy of LAIV for vaccine-matched strains was 57·5% (95% CI 43·6-68·0). The vaccine was well tolerated, and adverse events were balanced between the groups. The most frequent adverse events were tachypnoea (n=86 in the LAIV group and n=54 in the placebo group), cough (n=73 and n=43), and runny nose (n=68 and n=39), most of which were mild. INTERPRETATION: This single-dose Russian-backbone LAIV was safe and efficacious at preventing symptomatic laboratory-confirmed influenza illness due to vaccine-matched strains. LAIV programmes might reduce the burden of influenza illness in Bangladesh. FUNDING: The Bill & Melinda Gates Foundation.

Safety of Russian-backbone seasonal trivalent, live-attenuated influenza vaccine in a phase II randomized placebo-controlled clinical trial among children in urban Bangladesh.

INTRODUCTION: Live-attenuated influenza vaccines (LAIVs) have the potential to be affordable, effective, and logistically feasible for immunization of children in low-resource settings. MATERIAL AND METHODS: We conducted a phase II, randomized, double-blind, parallel group, placebo-controlled trial on the safety of the Russian-backbone, seasonal trivalent LAIV among children aged 24 through 59 months in Dhaka, Bangladesh in 2012. After vaccination, we monitored participants for six months with weekly home visits and study clinic surveillance for solicited and unsolicited adverse events, protocol-defined wheezing illness (PDWI), and serious adverse events (SAEs), including all cause hospitalizations. RESULTS: Three hundred children were randomized and administered LAIV (n=150) or placebo (n=150). No immediate post-vaccination reactions occurred in either group. Solicited reactions were similar between vaccine and placebo groups during the first 7 days post-vaccination and throughout the entire trial. There were no statistically significant differences in participants experiencing PDWI between LAIV and placebo groups throughout the trial (n=13 vs. n=16, p=0.697). Of 131 children with a history of medical treatment or hospitalization for asthma or wheezing at study entry, 65 received LAIV and 66 received placebo. Among this subset, there was no statistical difference in PDWI occurring throughout the trial between the LAIV or placebo groups (7.7% vs. 19.7%, p=0.074). While there were no related SAEs, LAIV recipients had six unrelated SAEs and placebo recipients had none. These SAEs included three due to traumatic injury and bone fracture, and one each due to accidental overdose of paracetamol, abdominal pain, and acute gastroenteritis. None of the participants with SAEs had laboratory-confirmed influenza, wheezing illness, or other signs of acute respiratory illness at the time of their events. CONCLUSIONS: In this randomized, controlled trial among 300 children aged 24 through 59 months in urban Bangladesh, Russian-backbone LAIV was safe and well tolerated. Further evaluation of LAIV safety and efficacy in a larger cohort is warranted.

Human metapneumovirus infection among children, Bangladesh.

We confirmed circulation of human metapneumovirus (HMPV) among children with febrile and respiratory illness in an urban slum in Dhaka, Bangladesh, during active surveillance in 2001. HMPV was the most common single virus identified among febrile children and appears to contribute to the high rates of illness in this population.