More Tests, More Cases

Pub. Date
18 March, 2021
Pub. Type

Main points

  • We produce timely estimates of the R number and report forecasts for new cases of Covid-19, hospital admissions and deaths due to Covid-19 using publicly available data on 16th March 2021.
  • Figure 1 shows that the Reproduction number, R, which is the average number of secondary infections currently generated by an infected individual, moved up to 0.85 – 1.0 by 15th March from a range of 0.85 – 0.95 where it had been the week before. This estimate is obtained after controlling for enhanced testing in schools that started when they reopened on the 8th of March. If enhanced testing in schools is not controlled for, the R estimate would be 0.9 – 1.05.
  • Based on our model, by 12th April when non-essential retail is scheduled to reopen, we expect trend value of daily cases to be around 2,900, admissions to be around 100 and deaths to fall below 50 (Figures 2-4). Relative to last week, forecasts for admissions and deaths are unchanged but that for cases is increased by 2,000. This is driven by our correction for increased testing due to schools reopening but also due to the increase in transmissions picked up in the data.
  • To the extent that the re-opening increases transmission these numbers may increase. At the same time, expansion of the vaccination programme can be expected to reduce transmission. The trajectory that nets out these opposing trends will become evident in the weeks to come.
  • Figure 5 shows that regional R number estimates are increasing. Currently, the West Midlands has the lowest R number while Scotland and Yorkshire and the Humber have the highest.

“Based on the latest data on new cases, our estimate of the R number for the UK lies in the range 0.85 – 1.0, taking it slightly above the range it has been from mid-January. This estimate is based on data up to 16th March 2021, about 10 days after the schools were reopened on the 8th of March. The reopening of schools in England has immediately increased testing and the resultant positive cases. Even after controlling for increased testing our estimate of the R number has moved up. In the period ahead, contacts and hence transmission can be expected to increase as a result of the reopening. and our forecasts for daily cases is likely to rise. The path of hospital admissions and deaths will depend on the follow through from increased transmission due to the reopening, countered by the efficacy of the vaccination programme as the roll out continues at pace.”