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Juggling vaccination numbers

At today’s press conference, the Vaccine Minister, Nadhim Zahawi, has been presenting some numbers:

He says 82% of adults have had a first dose, and 60% have had a second dose.

He says if 85% of all adults are double vaccinated, and the vaccines are 85% effective, then the protection level is 72%. That means 28% of the population would still remain unprotected.

UK Covid live: 16,135 new cases reported – highest total for more than 4 months | Politics | The Guardian

While all these numbers are correct, they need a bit of unpacking and unpicking. While they sound very positive – and, no doubt, the UK vaccination drive is amazing – they are hiding some slightly worrying facts.

Firstly, in the UK there are about 16 million people in the age band 0-19 years and 51 million people 20 years old and above. Assuming 82% applies to those aged 19 and above (and extrapolating England %s to the UK), this means 63% of the whole population. For the double dose, 60% of adults correspond to only 46% of the total population.

It is quite startling that the government is excluding young people and children from the calculations. I think we do have a pretty strong evidence that they also become infected and are capable of infecting. While the symptomatic proportion, hospitalisation and death rates are lower for younger people, it is naive – or dangerous – to exclude them.

Assuming further that the mix of the vaccines is 50% Pfizer/Moderna to 50% AstraZeneca, and the efficacies of 33% both types single dose, and 66% and 98% for two doses, we get 43% effectively protected and 57% effectively unprotected. This also assumes 100% Delta strain (which is not too far).

63%-46%=17% is only jabbed once and with 33% efficacy, it is only 5% population protected.

46% have double dose: 23% with Pfizer (22.5% effectively protected) and 23% with AstraZeneca (15.8% effectively protected).

Together, 5%, 22.5% and 15.8% yields 43.3%.

Adding to it perhaps 25% post-infection immunity and assuming random distribution of those among vaccinated, we get about 60% immunity in the whole population.

This is absolutely fantastic and is certainly already making a lot of impact on the spread of the Delta variant. In other words, Delta would have spread much quicker and possibly reached much further than we expect it to go.

But it also means that we are not yet safe and indeed that there is still quite a lot to do.

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