Abstract
SummaryBackgroundThe 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.MethodsBetween 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.FindingsOf 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.InterpretationThis 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.FundingThe Bill & Melinda Gates Foundation.
Highlights
The seasonal patterns, incidence, and severity of influenza virus infection are poorly defined in many tropical regions.[1]
In urban Kamalapur, which has a background clinical pneumonia incidence of 500 cases per 1000 child-years, community-based surveillance identified that 10% of children younger than 5 years with clinical pneumonia are positive for influenza virus.[4]
No participants were lost to follow-up before day 8. 1637 (92·9%) of study participants completed home follow-up visits to December, 2013, 1081 (92·0%) of those who received live attenuated influenza vaccine (LAIV) and 556 (94·7%) of those who received placebo (p=0·048)
Summary
The seasonal patterns, incidence, and severity of influenza virus infection are poorly defined in many tropical regions.[1]. Live attenuated influenza vaccines (LAIVs) are attractive for use in young children because they may be delivered intranasally and have good efficacy. In a WHOsponsored technology transfer programme, several manufacturers are developing reassortant LAIVs based on A/Leningrad/17 and B/USSR/60 master donor viruses. This initiative could provide affordable supplies of influenza vaccine in Bangladesh and other lowresource countries.
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