Work continues to develop Covid-19 vaccines effective against new coronavirus variants.
And some researchers are eyeing an even more ambitious goal: to create broad-spectrum vaccines protective against new types of virus - even before they emerge.
Researchers have warned, however, that there are significant technical hurdles to overcome before such “pan-virus” or “pan-coronavirus” vaccines could be released.
Here's what we know so far:
Why do we need a better vaccine?
Events in recent decades – and not just the latest pandemic – have highlighted the possible need for such widely applicable jabs.
In 2002, a novel coronavirus sparked the Severe Acute Respiratory Syndrome (Sars) epidemic, while the coronavirus responsible for Middle East Respiratory Syndrome (Mers) was first identified in 2012.