It's been a month since Coronacast took a break, and since then a lot has changed. The BA4 and 5 variants have become dominant, and immunologists are starting to worry about the state of play. Firstly, BA4 and 5 are acting a bit like new variants. They're evading vaccines and prior infections even more than original Omicron and there's no sign they're slowing down. And secondly, COVID case loads are surging and hospitals are feeling the pressure. So what else has changed over the last month, and what's the rest of winter looking like? Also on today's show: * I'm suddenly eligible for a fourth dose. Do I bother getting it? * Can you get the 2nd booster shot 28 days after having COVID (in line with information that re-infection can occur after 28 days), or is it still best to wait the 3 months, and if so, why is it best to wait? * I've had two AstraZeneca and one Moderna shots. What should I have as my fourth dose?