big factor in this change was a surge in cases in schoolchildren in the least deprived areas. But the same change occurred in older age groups, too. So what was going on?
There are many possible explanations, but one contributing factor is likely to be the fact that, having had high case rates for so long, more deprived areas had much higher levels of infection-acquired immunity. Essentially, so many people had had COVID already that the virus started to run out of susceptible people to infect. Many more affluent areas, however, had seen relatively fewer cases and so had greater exposure to new outbreaks, particularly among schoolchildren who didn’t have the additional protection of vaccines.
Unfortunately, there has been a major new development since then: omicron has arrived. The new variant appears to be even more infectious than previous variants of concern, and it has some degree of immune escape, which means it is much better at reinfecting people who have some degree of immunity, whether that is through having been infected or being vaccinated.
...
The fact that omicron can overcome the wall of protection that has been built up in deprived areas through such high levels of prior infection means that there is a risk that these inequalities are going to be repeated in the coming weeks and months. Just when it seemed as though there was a light at the end of the tunnel for many living in deprived areas, the light began to fade.