What do the UK data tell us about the Delta variant? Are the vaccines working?

There is a lot of talk in the media about how the Delta variant is bringing a third wave to many countries in the world. This variant has proven the most transmissible yet, spreading a rate more than double the original SARS-CoV-2 wild type variant, and it is quickly becoming the dominant strain in many places, already comprising nearly all cases in the UK and now comprising near half of the cases in the USA.

From these data, two claims have emerged and are spreading around social media:The vaccines don’t work, since >1/2 of COVID-19 deaths in the UK are from those who had been vaccinated. The Delta variant is mild and inconsequential, since the raw hospitalization and death counts are low, that we have no need to be concerned about it at all — it is as docile as a common cold and the media is just creating hype and alarm by discussing it. Ivor Cummins (whose past claims I’ve critiqued here) is pushing this argument, calling it the “Delta Deceit” To investigate these claims, we need to unravel information about cases, hospitalizations and deaths, and consider how they vary by age and vaccination status, and also consider how vaccination rates vary across age groups.

We need to aggregate information across all these factors to characterize the Delta variant and vaccine efficacy against it. Fortunately, the UK with its centralized healthcare system and rigorous electronic medical records (EMR) has extensive high-quality medical data on the entire population, and it has also ramped up the most extensive SARS-CoV-2 genetic sequencing efforts in the world, sequencing more than half of confirmed cases.

This gives the UK the best variant-specific data in the world. The UK also has an excellent scientific team that is keeping an eye on these data and writing frequent reports of key observations, including technical briefings for variants of concern (VOC) that they share with the public on accruing knowledge on the emerging variants.

In this blog post, I will unravel what the UK data tell us about the Delta variant and vaccines, relying heavily on information provided in the UK COV technical briefing #17 written on June 25, 2021, and also integrating in other data and data summaries I have encountered that I have found useful.

In summary, the data make it clear that:The UK has an extensive sequencing program that enables population-level analysis by variants that is not possible elsewhere.

Delta has taken over the UK, quickly dominating all other variants.Delta infections are happening almost exclusively in the young, with only about 10% in adults >50 years old

.Nearly all adults >50 years old are fully vaccinated, while only <30% of adults 50% of COVID-19 deaths being among the vaccinated can be explained by the fact that the vaccine is not perfect, most unvaccinated are young, and older people are in general at a much higher risk of death of infection.

Unvaccinated countries are likely to experience much higher transmission and death rates than what has been experienced in the UK, so this Delta variant should not be taken lightly just because the vaccines have taken the edge off it in the UK.After presenting these data, I will briefly discuss what this information means we can expect in the USA as the Delta variant takes over this month.

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