The Lancet Global Health, July 2019, published a study investigating the effectiveness of inactivated trivalent influenza vaccines with limited resources.

The researchers conducted a randomized controlled trial in three villages in India. The cluster is defined as a family and the age limit is for children between 6 months and 10 years of age during the study period. At the beginning of the study, families were randomly assigned (1:1) to the intramuscular injection of the inactivated trivalent influenza vaccine (IIV3) group or the inactivated poliovirus vaccine (IPV) control group; vaccination was performed once a year and continued 3 years. The primary effective outcome was the diagnosis of influenza in vaccinated children with febrile acute respiratory disease, which was analyzed in a modified intention-to-treat population (ie, children who received at least one dose of vaccine, monitored, and after the next vaccination, No influenza infection within 15 days). A secondary outcome of indirect efficacy (monitoring studies) was that unvaccinated family members of vaccination study participants had febrile acute respiratory disease. The annual data is analyzed separately(first year: November 2009 to October 2010; second year: October 2010 to October 2011; third year: October 2011 to May 2012). Safety and efficacy in all participants who received at least one dose of vaccination. The trial is registered with and is numbered NCT00934245.

During the period from November 1, 2009 to May 1, 2012, researchers recruited 3,208 households, of which 1959 had children who met the vaccination criteria. 1010 households were assigned to the IIV3 group and 949 households were assigned to the IPV group. In 3 years, the researchers were 4,345 children (2,132 inoculated with IIV3, 2213) from 1868 households (968 households in the IIV3 group, 900 in the IPV group, including 10813 unvaccinated household contacts). IPV) was vaccinated. In the first year, 151 (10%) of the 1572 IIV3 vaccinates detected influenza virus, and 206 (13%) of the 1633 IPV vaccinates detected influenza virus. In the second year, 105 out of 1705 IVA3 vaccinates (6%) and 182 out of 1814 IPV vaccinates (10%) had flu had influenza. In the third year, 20 (1%) of 1670 IIV3 vaccinates and 81 (5%) of 1786 IPV vaccinates had influenza . In the first year, the total vaccine titer against influenza A (H1N1) pdm09 was 14.5%. In the second year, the total vaccine potency against influenza A (H3N2) was 64.5%. The total vaccine potency against influenza B was 32.5% in the first year, 4.9% in the second year, and 76.5% in the third year.Indirect vaccine titers were only found in 39 of 1432 individuals (1%) who were not vaccinated in the IIV3 group and 60 (1%) of the 4121 IPV group unvaccinated individuals. It was statistically significant at the third year. In the IIV3 group, 225 (12%) of the 1,632 children in the first year, 375 (22%) of the 1,718 children in the second year, and 209 (12%) of the 1,673 children in the third year Adverse reactions (216% (13%) of 1,730 children, 380 (21%) of 1,825 children, and 235 (13%) of 1796 children, respectively, in the IPV group). The most common reactions in the two groups were fever and tenderness. There were no vaccine-related deaths in either group.

The study concluded that IIV3 provides a variety of direct and indirect protective effects for influenza infection and should be considered when quantifying the effectiveness of vaccination programs.

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