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This week we feature an article on the influenza vaccine — perfect for flu season. Enjoy!
Instructions to access: Copy and paste the article title into UBC Summons to read the full article.
Seasonal influenza affects individuals of all age groups; however, adults 65 years of age or older, are particularly vulnerable to influenza-related complications including hospitalizations and deaths. Although influenza vaccine is the most effective intervention in prevention of influenza related complications, the antibody response and protection elicited by the standard dose vaccine are lower in older individuals than younger adults. Increasing the amount of the antigen in the vaccine is one of the strategies to improve antibody response in older individuals. A total of 31,989 participants aged 65 years or more were included in a 2-year multicenter, randomized double-blinded study. The participants were randomly assigned to the high dose (HD) or standard dose (SD) of the trivalent, inactivated influenza vaccine (IIV3) in a 1:1 ratio. The trivalent vaccine protects against three influenza viruses – influenza A (H3N2) virus, influenza A (H1N1) virus, and one influenza B virus. Also, approximately 1/3rd of the participants were randomly selected to be in the immunogenicity subset. In the immunogenicity subset, blood samples were collected from the participants 28 days after vaccine administration. The primary efficacy end point for this study was the occurrence of laboratory confirmed influenza caused by any influenza viral types or subtypes at least 14 days after vaccination. In the intention-to-treat analysis, 228 participants in the IIV3- HD group (1.4%) and 301 participants in the IIV3-SD group (1.9%) had laboratory- confirmed influenza caused by any viral type or subtype associated with a protocol-defined influenza-like illness (relative efficacy, 24.2%; 95% confidence interval [CI], 9.7 to 36.5). The overall efficacy of 24.2% against the primary end point indicates that about one quarter of all breakthrough influenza illnesses in this population could be prevented if IIV3-HD were used instead of IIV3-SD. Significantly fewer IIV3-HD recipients than IIV3-SD recipients reported serious adverse events including pneumonia, cardiorespiratory conditions, emergency health-care visits; which suggests that IIV3-HD may protect against the occurrence of influenza-related serious events. Moreover, the immunogenicity subset confirmed that the sero-protection rates were significantly higher in the IIV3-HD group. Overall, the study concluded that among persons 65 years of age or older, IIV3-HD induced significantly higher antibody responses and provided better protection against laboratory-confirmed influenza illness than did IIV3-SD. These clinical findings can be taken into account by health-care professionals and be utilized for public health benefit.
– Harpreet Bahniwal
B.Sc. (Pharm) Candidate 2016