November 30, 2021 - Lessons Learned from Delta

Lessons Learned from Delta

November 30, 2021

Amid all the sound and fury surrounding the Omicron variant, we cannot forget that Delta remains the big shot around the world, constituting more than 99% of the total analyzed sequences over the last 2 weeks in the United States, U.K., Germany, Spain, India, Brazil, Italy and Australia. This fact alone explains a lot about the current Covid situation in Alabama.

Since my last newsletter on Friday, Alabama has reported a total of 737 positive cases, or just 184 cases per day. Over the last 14 days, Alabama has seen a daily average of just 6 cases per 100K population, tied with Florida and Hawaii for the lowest per capita infection rate in the nation over that 14-day period. Our hospitalization rate is 3.1 patients per reporting hospital, slightly above our low of 2.7 patients per hospital a few days ago, but lower than 43 other states.

How is Alabama’s recent success possible, considering that only 46% of Alabama’s population is fully vaccinated? One plausible explanation is that the Deep South, in general, and Alabama, in particular, were absolutely decimated by Delta a few months ago, much worse than elsewhere in the U.S and Europe. Every single day from mid-July through the end of September, the South led all regions of the country in per capita cases. From July 29 to September 10, the South had more than twice as many new cases per capita as the Midwest and Northeast and nearly twice as many as the far West.

For instance, on September 1, the Deep South averaged 77 new daily cases per 100K population, compared to 41 per 100K in the far West, 38 per 100K in the Midwest, and 25 per 100K in the Northeast. (Alabama averaged over 100 new cases per 100K population throughout late August and September). It wasn’t until September 30 when the case rate in the Midwest (38 per 100K) finally surpassed the rate in the Deep South (37 per 100K).

Ironically, Alabama’s recent good fortune may be due in part to this earlier wave of infection. States in other regions of the country are seeing a spike partly due to waning vaccine-induced immunities. Likewise, western Europe’s recent spike may be related to lower levels of infection this summer and waning vaccine-related immunities, combined with winter seasonality. Alabama, however, benefits from higher natural immunities resulting from its horrific prior experience with Delta. Of course, we paid a high price for those natural immunities: overrun intensive care units and a death rate second only to Mississippi.

So, as we face the threat posed by Omicron, what lessons have we learned? It seems likely that Omicron is more transmissible than Delta, but it is too early to know if Omicron could also be as virulent as Delta - hopefully not. Although Omicron carries worrisome mutations that may help it evade antibodies which people have acquired either from vaccines or from prior infection, existing vaccines are expected to provide at least some protection because they stimulate not only antibodies but also immune cells that can attack infected cells (mutations to the spike protein do not blunt that immune-cell response).

According to Dr. William Hanage, an epidemiologist at the Harvard T.H. Chan School of Public Health, existing vaccines remain vital weapons against Omicron, both by slowing down its spread and making it more likely that people who do get sick will only have mild symptoms. Omicron is “certainly enough to take seriously, but it’s not apocalyptic,” he said. “It’s not a magic virus. Magic viruses are not a thing.” The totals:

11/16 - 542

11/17 - 496

11/18 - 492

11/19 - 473

11/20 - 680

11/21 - 272

11/22 - 253

11/23 - 619

11/24 - 416

11/25 - Not reported

11/26 - 398

11/27 - 357

11/28 - 157

11/29 - 176

11/30 - 477