Vaccine efficacy (Part II) and Delta hits close to home


Emily Boerger


Since April 2020, Anchorage-based economist and leadership coach Jonathan King has written a weekly email to clients and friends digesting Alaska’s most recent COVID data and bringing to light relevant information he thinks will benefit his stakeholders. This week he shared his thoughts on the challenges of calculating, and communicating about, vaccine efficacy under the Delta variant.


Stay one step ahead. Join our email list for the latest news.



Vaccine Efficacy (Part II)

Last week I published this statement and accompanying link:  Since January 1, 94% of all cases, 94% of all hospitalizations, and 97% of all deaths to date were in people who were not fully vaccinated. A version of this statement is published every week in the AK HSS Alaska Weekly COVID Update and it has appeared many times in print in other publications.  The statement is completely factual.  However, it doesn’t tell the whole (or current) story because 1) In the month of January almost no one in Alaska was fully vaccinated against the disease (which means the statement skews the dominator of total cases against the unvaccinated status) and 2)  the statement covers a large period of time when the primary variant in Alaska was something other than the Delta variant (The data indicate that Delta is functionally now the only variant circulating in Alaska (see below)).



There is increasing evidence that the vaccines are not 90%+ effective in preventing symptomatic infections against Delta as the were against Alpha. Every week there are new studies on this topic and they are consistently estimating a 45-60% efficacy rate (blended across all vaccines). These studies give a slight edge to the Moderna vaccine which scientists may be because of Moderna’s “delayed second injection” protocol.  In short, there’s evidence that delaying the second injection results in a more durable immune response.  This data is one reason why multiple governments are considering booster shots. Booster shots are a story for another time,  what I’m really interested in is the efficacy of vaccination against Delta COVID and what the state’s data are telling us. They tell a very different story than the lead line of Since January 1, 94% of all cases, 94% of all hospitalizations, and 97% of all deaths to date were in people who were not fully vaccinated. The story that we should be communicating is “Alaska data show that vaccination is highly effective in preventing death and hospitalization from the Delta variant, but the vaccinated need to be aware that prevention against symptomatic infection is lower than with the Alpha variant.” This message is inconvenient and more complicated; the two often walk hand-in-hand in a data informed world but make messaging harder.

Over the last several months AK HSS’ Alaska Weekly COVID Update has published vaccine breakthrough (VB) and unvaccinated case, hospitalization, and death data.  The reporting is a bit choppy and contains some typos that make constructing a week-to-week visual difficult.  However, using the VB count data and the published daily count data I was able to construct the table below which shows case, hospitalization, and death counts by vaccination status from either July 10 or May 10 depending on the quality of the data AK HSS published. I then calculated an odds ratio (Unvaccinated Occurrence-to-Vaccinated Occurrence) and a vaccine efficacy estimate. Both of these estimates are adjusted for percentage of population vaccinated/unvaccinated (presuming 45% average fully vaccinated since July 10 and 43% since May 10). The data show that fully vaccinated status “in the heart of Delta” reduces the risk of being a diagnosed case by 61%, of hospitalization as a case by 75%, and of dying by 91%.  The case efficacy of 61% is in line with the most recent data. The hospitalization reduction of 75% is a little lower than data seen from other locations, but it could be a result of an Alaska-specific factor or the small size of the dataset. The 91% reduction in fatalities is in line (perhaps a bit low) of what the data show for other locations. The other factor in this analysis is Jonathan. I’m shooting from an (educated) hip here. I’d love for AK HSS or an epi expert at UA to provide initiate a more thorough analysis.



The Numbers (Graphically)

The Delta variant and human behavior are continuing to drive cases higher both in Anchorage and for the rest of Alaska.  The Anchorage 7-day case rate of 136.4 is as high as it’s been since December 23, 2020 while Alaska’s 7-day case rate (301.1) is back to January 9th levels.  The rates’ rates of growth (say that 5 times quickly) are slowing, but we’re still increasing the case rate at 40 percent every two weeks. As a reminder school starts next week. I don’t think we top out in terms of case rate until sometime in September.



The number of currently hospitalized continues to grow. Current hospitalizations are at roughly 75% of the November peak and ICU space is very, very limited (particularly in the Anchorage area). We have weakened the link between cases and hospitalizations, but we will not fully break it until we’re all vaccinated or have durable acquired immunity.  The hospitalized are younger, stronger, and sicker than the hospitalized in the first wave.  These factors mean they’re less likely to die and more likely to stay in the hospital longer.



COVID Hits Close to Home

Two weeks ago the amazing wife’s unvaccinated (grumble) cousin and husband visited the cousin’s unvaccinated father and vaccinated mother in Florida. They brought COVID with them and returned to Houston (via air) symptomatic, but undiagnosed. The day after they left both the father and mother were diagnosed with COVID. The father is now lying in the hospital incoherent and on oxygen. The vaccinated mother has avoided the hospital. The amazing wife’s father and mother (both vaccinated) live a mile from the aforementioned Aunt and Uncle. Her father, who is immunocompromised, was diagnosed with COVID last Thursday after visiting the aunt and uncle, but has avoided the hospital. He’s in far better shape than his unvaccinated counterpart even though he’s a decade older, immunocompromised, and has COPD.  Her mother has, thus far, avoided contracting the virus.  A solid reminder that it just takes one infected individual to spark a brush fire and that vaccination saves lives.

On a much more minor note, when I was a teenager the tunes emanating from my car were from Nirvana and Pearl Jam. A couple weeks back I heard the Foo Fighters (headed by Nirvana drummer Dave Grohl) on the radio and I swore that if they ever came to Alaska I would buy tickets. Well, that day tickets went on sale for the Foo Fighters concert this coming Tuesday at the Denaina Center. With Delta climbing the way that it is, and with documented indoor spread amongst the vaccinated, the concert should be postponed. I’ve got four tickets and Team King won’t be in attendance. It’s just not a great choice to be indoor for three hours with 3,000 screaming fans. It hurts, but I’ll see my Fighters another day. For anyone else who might be foregoing the same opportunity I give you the “Kiss Guy” performance and the obvious connection with the fans that makes Dave Grohl so amazing.

Wear your mask, enjoy the end of summer, rock out at home.