COVID isn't over yet

To judge from the recent Omicron experience in Europe, weathering another surge without much disruption or dying may require that vaccination levels and regular boosters among the elderly get pretty close to 100 percent. The U.K. managed Omicron relatively well with only 71 percent of its overall population double-vaccinated but 93 percent of its seniors. More than half of the country as a whole has gotten boosted compared with just 29 percent in the U.S. This is partly why recent data from the U.K. is a bit more curious than that coming from Hong Kong. There, over the past few weeks, hospitalizations have begun to grow steadily in all regions of the country after a post-Omicron lull. The growth isn’t huge — 21 percent week over week — but it is visible everywhere.

The explanations are not so obvious — a reminder that, more than two years into this pandemic, there are still things about spread dynamics we don’t understand. At first, given low case levels, the rise in hospitalizations was attributed by some analysts to waning booster effects among the elderly many months after that rollout began. But there does not seem to be a clear sign in seroprevalence data that antibodies are declining at the moment. Behavioral changes may be playing some role with the recent lifting of Omicron restrictions, but case growth does not seem to be concentrated in any subgroup. Instead, it appears consistent across all age groups and regions. And while the Omicron sub-variant BA.2 has been growing as a proportion of British cases for a while now, presently accounting for more than half of new cases, it is not creating a major new wave of cases, and there are few clear signs it produces meaningfully different outcomes than the original Omicron, BA.1. A final hypothesis says hospitals are simply picking up more incidental COVID; having resumed normal operations post-Omicron, more people are coming to the hospital for other kinds of procedures, and some percentage of them are popping up as positives. (This would explain the lack of a lag between case growth and hospital growth.) But even isolating those cases, admissions for COVID are ticking up, too, if by a smaller degree.