Can Omicron evade our vaccines?

As the days tick by since Omicron was discovered, it's slowly spreading around the world.One example is reports of a couple of Israeli doctors who likely picked up Omicron in the United Kingdom, before flying back home.Their symptoms are said to be mild at the moment, but more worryingly, both of the doctors were fully vaccinated with Pfizer - that's all three doses.So what do we know about how Omicron works with our current vaccines? Also on today's show:* If we have been vaccinated to recognise the spike protein, why are variants so concerning? Is it the spike that changes?