BA.2 - A new Bad Boy or just your run of the mill Scariant?

Well by now you have probably read the latest output on BA.2, previously referred to as Stealth Omicron and perhaps Son of Omicron. The initial reading from many in the press, taking their cue from virologists and epidemiologists is, don’t panic this doesn’t look so bad. That may well be the case, let’s hope so, but just a short time ago the reassuring message from the media was Omicron is mild, hardly more than a cold. That view has aged like a quart of milk in the sun, so perhaps we all shouldn’t jump to conclusions. At the risk of boring you, let’s review what we think we know about BA.2. First sequenced in South Africa this variant of the Omicron lineage has spread widely through the world and over 100 cases have been sequenced in the United States from 27 states. It is easily distinguished from Omicron by its lack of S gene drop out on PCR, as long as other variants with a similar signature are not circulating in your area at the time. BA.2 has been spreading rapidly in the UK and Europe and clearly has some transmissibility advantage over Omicron. I don’t think we have a good handle on the magnitude of that advantage yet, although numbers have been suggested from epidemiologists in the UK and Denmark. The Founders Effect can tend to magnify the apparent advantage of a new variant for a period of time, so let’s just say it spreads a bit more efficiently than Omicron, but nothing like the increased transmissibility of Omicron compared to Delta or Wuhan. If it had that sort of advantage it would have replaced Omicron completely in the UK by now. So far the epidemiologists in the UK are reporting that it does not appear to be more virulent in terms of hospitalization, and there are indications that it does not have more prior immunity escape potential than Omicron. That all sounds very nice, but we are early in the game. There is at least one thing that concerns me that these early optimistic reports don’t seem to focus on. When you look at the curves of newly diagnosed cases in places where BA.2 has been spreading, Denmark stands out for several reasons. The new variant has spread particularly rapidly there, and is now 65% of the circulating virus, much higher than the level reported yet from other European countries and the UK. When we look at the curves of new cases from these countries we find that the Omicron surge has peaked and is receding in the UK, Spain, France, and the US. The Omicron surge appears to have started relatively early in Denmark, around Dec. 5 or so, but we don’t see a plateau in new cases there yet. Denmark’s 80% vaccinated and 60% boosted population of 5,800,000 citizens are getting infected at a rate close to 1% per day with no let up so far. Is this just coincidence or a signal that BA.2 is having a real impact on the trajectory of Denmark’s Omicron wave, dragging it out, with an ultimately higher peak and longer tail? I think a short interval should make this clear, but it is intriguing that other countries which were early to the Omicron wave, but at least so far have a much lower frequency of BA.2, have peaked and are on the downslope. The Danes don’t seem to be impressed, this country which embraced strict mitigation efforts have announced that they are abandoning basically all restrictions, including masks in public places, starting next week. There is a tone of resignation in their announcement. They seem to be acknowledging that there is nothing they can do to stem the rising infections despite their high vaccination rate, and since the hospital system is coping with the current surge they are essentially throwing in the towel.