During the pandemic, it will be more important that everyone over 6 months of age get vaccinated against influenza so as not to use up limited medical resources on a preventable illness. Furthermore, influenza might potentiate the severity of COVID-19. Yet, many question the need for an annual vaccine. How effective is the flu vaccine? Campbell et al (10.1542/peds.2020-1368) studied this by looking at the effectiveness of the 2018-19 influenza vaccine that was targeted against three predicted strains of influenza A and B, but was not designed to target an antigenically drifted A (H3N2) strain that appeared to predominate in the second half of the flu season. The authors looked at 1792 hospitalized children at 7 hospitals between the ages of 6 months and 17 years and at 1944 children seen in their emergency departments during the 2018-2019 flu season. They obtained vaccine status from parental report in the ED, as well as state immunization registries or provider records for inpatients and then tested children for influenza confirmation using molecular assays.
The results of this study demonstrated 41% overall vaccine effectiveness for hospitalized patients and 51% overall effectiveness for those children seen in the ED. Effectiveness was even higher against the selected strains contained in the 2018-19 vaccines. The vaccine also proved effective in those children who developed flu from strains not in the vaccine. If you are a pessimist, you would say that 60% of children vaccinated still developed signs and symptoms of influenza serious enough to need a visit to the ED or a hospitalization. If you are an optimist, you could say that the flu vaccine reduced hospitalization and ED visits by 40-60% despite the antigenic drift that occurred in 2018-19. Hopefully you will understand the real benefit of the vaccine and advocate for all your patients and yourself to get the vaccine this fall even if it turns out not be as highly effective as predicted. Link to this study and share these findings to help families understand the benefit of influenza vaccination, which is immensely more important during the pandemic.
