Vaccination is the primary strategy presently used to prevent influenza infections. However, developing and implementing a new vaccine will be difficult if a novel highly pathogenic influenza virus arises in people as major illnesses. H7 subtype influenza viruses have identical hemagglutinin epitopes, which can result in cross-reactive antibodies. A meta-analysis of antibodies produced by one H7 subtype influenza vaccination against other H7 subtypes was done in this study. PubMed, Cochrane Library, EMBASE, MEDLINE, Chinese Biological Medicine Database (CBM), and Wanfang databases were searched. This meta-analysis includes 9 papers with a total of 811 human participants. All H7 influenza vaccinations tested elicited vaccine strain-specific protective antibodies. All H7 influenza virus monovalent vaccinations proved positive for cross-reactivity to other H7 subtype viruses using the hemagglutinin inhibition test (HI), microneutralization test (MN), and immunosorbent assay (ELISA). Cross-reactive antibodies against other H7 subtype influenza viruses were induced by H7N1, H7N3, H7N7, and H7N9 vaccinations. The pooled SCR of H7N1 and H7N3 vaccine cross-reactivity was 0.88 and 0.40, respectively. The combined SPR of H7N1 and H7N7 vaccines was 0.89 and 0.93, respectively. 

Cross-reactive antibodies against H7N9 viruses were produced by all H7 vaccinations. When a new highly pathogenic H7 virus emerges, H7 vaccinations can be utilized to reduce influenza infection.

Reference: https://www.tandfonline.com/doi/full/10.1080/21645515.2019.1649551