Editorial

Influenza viruses continue to take a heavy toll on public health worldwide. Despite prior infections or vaccinations, a hugely variable nature of the viruses (antigenic drift) and the frequent exchange of genetic materials among different strains (antigenic shift) leave the most human population vulnerable to subsequent infections. In par-ticular, antigenic shift occasionally gives rise to a novel virus to which most human population has little pre-exiting immunity, causing a fatal damage to human health globally, as seen in past pandemics [1]. To be better prepared for influenza infections, considerable efforts have been made to develop a universal vaccine that provides a broad-spectrum protection against a va-riety of influenza viruses. While the strain-specific protection of a vaccine heavily re-lies on the hemagglutinin (HA)-inhibitory or viral-neutralizing antibodies that block the attachment of the HA of the virus to the host receptors (sialic acids), this is not a reliable approach to design a universal vaccine, especially because the globular head domain of the HA is considerably variable and therefore can easily escape from neu-tralization by pre-existing antibodies. It is not surprising that recent major advance