To kick-off the conversation with @BillGates, what scientific or tech breakthrough would make the biggest difference now to ending the COVID pandemic?

@devisridhar The vaccines we have prevent severe disease and death very well but they are missing two key things. First they still allow infections ("breakthrough") and the duration appears to be limited. We need vaccines that prevent re-infection and have many years of duration.#

@BillGates Agree 100%- next gen vaccines with sterilising immunity. 2nd question: What are the current challenges in reaching global vaccination access? What are the obstacles?