A: Unvaccinated people, for the most part.
Q: Will the “delta” variant change that?
A: Not likely.
As new cases of COVID-19 continue to decline in the US 🇺🇸and Canada 🇨🇦, but are rising steeply elsewhere (UK 🇬🇧and South Africa🇿🇦, we see you 🤗💕!), you might be wondering who is bearing the burden of new cases.
The answer is pretty straightforward: Most new COVID-19 cases in most settings are among people who aren’t fully vaccinated.
🧮A concrete example might help here: In King County, Washington (a large county of 2.3 million people including Seattle), epidemiologists analyzed 15,397 cases of COVID-19 from April and May 2021 (see linked story here).
📈During that time period, King County crossed the 50% vaccination mark. If vaccines didn’t protect people from COVID-19 at all, we might expect to see the cases split about 50/50 between vaccinated and unvaccinated people.
😮But that’s not what happened. Of the new cases in King County in March and April, 14,895 — 96.7% — were among people who were not fully vaccinated at the time of their diagnosis. Similar results were found for Washington State as a whole, and in Oregon.
📰We can also see a similar trend at the population level: A Washington Post analysis (linked below) looked at the relationship between county-level vaccination coverage and COVID-19 rates. The relationship was strong: High vaccination rate counties had low and declining numbers of cases. Counties with low vaccination coverage had high and increasing case rates.
🦠This same effect can be seen in the UK, which has among the highest vaccination coverage rates in world as well as steeply rising COVID-19 cases, likely due to the very infectious delta variant of the virus. In an analysis of 33,206 delta variant COVID-19 cases in England (part of the UK) from early February through early June 2021, only 1,785 — 5.3% — were among the fully vaccinated. (See super nerdy 🤓tweet thread about this analysis from James Ward linked below!)
💉💉While we hate to see cases climbing in the UK, this analysis confirms the effectiveness of available vaccines against the delta variant, and confirms the added protection from complete (two-dose) vaccination over just one dose.
🧑🏿🤝🧑🏽Bottom line: Vaccination offers excellent individual protection against COVID-19, and high vaccination coverage in the population is our best route to driving down transmission and ending the pandemic.