Public holidays are difficult for epidemiologists because people may avoid or delay testing and hospital visits. The latest Covid data from the government is clear. Omicron is the main cause of new infections in England, meaning that its effects are driving the epidemic. Its rate of growth appears to have slowed considerably.
Three weeks ago, Omicron infections were doubling every two days. If the rate of increase continued, we would have 1 million infections per day by now. The Christmas holiday can't explain the difference between the estimate and the most recent infections in England. Hopes that the epidemic peak might have been seen before Christmas were premature. The rate of increase is still increasing, but it is not as high as previously thought.
The epidemic has moved through different age groups, and we can see that in the data. In the last few days before Christmas, the rate of increase in the 20-to-40 age group slowed down, as infections increased most rapidly in the mid-December. The rate of increase in infections in this age group increased substantially in the 10 days before Christmas, despite the fact that the first half of December was relatively flat.
The number of beds occupied by people with Covid in England has risen by 42% in the last two weeks, as admissions have risen in this older age group. The number of patients with Covid occupying mechanical ventilation beds is still fairly level, but is actually below what it was a few weeks ago. The most recent data for England was 758 on December 28th.
Deaths within 28 days of a positive Covid test are still falling, but we wouldn't expect to see any impact on the death statistics from the recent rapid rise in Covid.
It's not clear how the next few weeks will play out in the UK. Even though the Omicron variant appears to be less severe than Delta, it's still not the case for everyone. The amount of pressure on the health service will depend on how many people become ill enough to be admitted to the hospital and how much of a problem the infections are.
If the cases increase very rapidly, peak and fall rapidly, then the pressure on the health service may be short-lived. The epidemic in the UK may not be as bad as in South Africa.
Where does this leave us with the knowledge to best manage as we move on? It all depends on how much Omicron puts on the health service at its peak and how long that period of high demand lasts. We don't know what will happen in January until after the holiday period.
Interventions and measures that reduce the transmissibility of an infection will reduce the peak, but are often associated with a longer- lasting epidemic. Social distancing measures may not prevent infections but may delay them.
If new treatments or new vaccines are expected to reduce death or severe disability, there can be other important gains from delaying infections. There is nothing that will make a big difference soon.
The effectiveness of the vaccines is affected by time. According to recent data from the UK Health Security Agency, the protective effect of the booster shot may be waning. It is more effective against severe disease than it is against mild infections.
Interventions are a matter of fine timing. It is not clear how this wave will play out. The UK government decided not to introduce new measures before the new year and instead to wait and monitor hospitalisations. The US CDC reduced the recommended isolation period for people with a positive Covid test from 10 to five days. If soaring infections no longer mean mass hospitalisation and death, this may mean a new preference for less restrictive policies.
The University of East Anglia has a professor named Paul Hunter.
The headline of the article was changed on December 30, 2021, to reflect that it was about England, not the UK.
