Vaccines and Many Measures
Jason Hunter, a campaigner, claimed:
You’d never believe this world beating UK vaccine programme if it were not for UK news and media telling you it was ‘world beating’ and that ‘Boris Johnson is doing a great job’ with vaccines…. because the data says that is just NOT true.
The graph shows the cumulative share of people ‘fully vaccinated’. That means people receiving both doses of two-dose vaccines. Similar claims spread on social media.
This claim does not reflect different dosing strategies.
Vaccines induce immune responses, giving our bodies a training exercise. Over time, protection wanes. Secondary doses help provide a more complete ‘memory’ response.
Most people get some protection from the first dose. This is shown when we compare estimated efficacy from the first dose alone to the full course.
The Pfizer-BioNTech trial suggested an efficacy of about 52% between the two doses. Immune responses were likely to be mounting. The Israeli vaccine programme shows high effectiveness. After two doses, estimated trial efficacy was about 95% (90% to 97%).
The UK has a high proportion of people with first doses. By 14th February, over 22% of the UK population received at least one dose. In Malta, that share was 8%. For France, Germany and Ireland, it was under 4%.
Like a collage filmmaker, opponents opine: ‘But this was a fantasy.’
On the measure of full vaccinations, the UK lags behind. That results from the JCVI’s recommendations to bolster short-term impact.
With each dose, we should seek to reduce the marginal risk of death. Giving one person two shots means another gets no vaccine. With limited vaccines, this is an optimisation problem.
In the beginning, the optimal strategy is to prioritise first doses for at-risk people. That holds for plausible expectations that protection does not dissipate in 12 weeks. Afterwards, the most vulnerable need extra protection with second doses.
Suppose we were unsure about the best stratagem for vaccinations. The UK also has sustained high levels of dose delivery.
In data analysis, there is often more than one measure that matters.