Health Secretary Matt Hancock revealed some statistics in the Commons yesterday about the Delta (Indian) variant: out of 12,383 Delta variant positive tests in the U.K. up to June 3rd, 464 went to emergency care and 126 were admitted to hospital. Of those admitted to hospital, 83 were unvaccinated, 28 had had one jab and three had had both doses.
Keen-eyed readers will spot that 83+28+3 is not 126 – there are 12 hospital admissions unaccounted for. A Department of Health source told the Financial Times‘s Sebastian Payne that nine of these “don’t match to a vaccine status at present” while three were within 21 days of their first dose so didn’t count in any category.
Can we use these figures to make some crude calculations of the severity of the Delta variant?
126 hospital admissions out of 12,383 positive tests gives a 1% hospitalisation rate, or 99% not needing hospital. How does this compare to the Alpha (British) variant?
Last week Public Health England (PHE) released a study claiming the Delta variant had around double the risk of serious disease or hospitalisation compared with the Alpha variant. However, according to the ONS, during the winter peak when the Alpha variant was dominant, around 2% of the population of England was infected with COVID-19 and around 0.04% of the population was being admitted to hospital with the virus each week, giving around 2% of British variant infections leading to hospital admission. This is double the rate for the Indian variant on Hancock’s figures – and furthermore, Hancock’s figures use positive cases, not an ONS population infection estimate, which would reduce the hospitalisation rate for the Indian variant further.
However, what we don’t know, because these are just statistics delivered verbally in Parliament not a proper report (more science-by-press-release), is how many of the 12,383 positive cases are too recent to have led yet to hospital admission. We also don’t know how elderly or vulnerable those in the sample of 12,383 are, or what impact the vaccines are making on the hospitalisation rate.
The figures are of limited use as well in estimating the effectiveness of the vaccines against hospital admission with the Delta variant. That’s because we don’t know what proportion of the 12,383 infected were vaccinated, so we can’t control for that key factor. Having said that, the three versus 83 hospital admissions for fully vaccinated versus unvaccinated seems encouraging.
Overall, this data is very limited. Nonetheless, the fact that the hospitalisation rate even among positive cases is so much lower with the Delta variant now than with the Alpha variant in winter is further evidence that the latest scariant is nothing to fear.