Israel’s experience provides some clues
As we get closer to achieving herd immunity in Arizona (see last week’s post) we will hopefully (at some point) begin to see cases decrease even in the absence of required or voluntary mitigation. We’re clearly not there yet as evidenced by our steadily increasing cases and an R0 of about 1.2 (AZ had more than 1,000 cases Saturday).
Up until now, we had to guess what the vaccination threshold is in order to achieve herd immunity. No longer. We now have one country that has achieved herd immunity mostly via vaccination: Israel. As the first country to achieve this via vaccination, their experience can shed light on what Arizona needs to do in order to get to herd immunity.
Note: The West Bank and the Gaza Strip are nowhere near herd immunity. As of last week, they had received only 37K doses of Pfizer and 24K doses of AstraZeneca from COVAX and 100,000 doses of the Sinovac from China for distribution to their more than 5 million people- enough vaccine for 1.5% of their population). Pfizer vaccine is being offered to Palestinians living in East Jerusalem.
The dominant strain of the SARS CoV2 virus in recent weeks in Israel has been the B.1.1.7 strain which is 45% more transmissible than the wild-type strain. In that way Israel and Arizona are similar (B.1.1.1.7 is rapidly becoming dominant in Arizona- see TGEN’s variant tracker). Israel and AZ are similar on other ways as well.
Both AZ and Israel prioritized seniors for vaccine and both are mostly using mRNA vaccines (Israel is exclusively using Pfizer). Both had large surges of infections over the last year, although Arizona performed much more poorly because of the policy decisions made by our governor and health director.
What can we learn from Israel’s experience that might predict Arizona’s future?
A recently published study entitled BNT162b2 Vaccination Effectively Prevents the Rapid Rise of SARS-CoV-2 Variant B.1.1.7 in high risk populations in Israel found a sharp decline in cases among seniors in Israel when ~50% of seniors were 2-weeks post their 1st vaccination dose. As they passed through the 50% vaccination threshold in other demographic groups, they began to see a substantial decline in transmission among that cohort, finally achieving population herd immunity.
How is Arizona comparing – and how close are we to achieving 50% coverage? Here’s the percentage of Arizonans that have been vaccinated in Arizona by age group:
Age % Vaccinated
15-24….. 21%
25-34….. 29%
35-44….. 36%
45-54….. 42%
55-64….. 57%
65-74….. 77%
75+……. 80%
Overall, about 41% of all adult Arizonans have been vaccinated with at least one dose (about 3 million have received at least one dose- with about 2.3 million fully vaccinated). Here’s the case breakdown by age group:
Age % of Total Cases
20-44……… 59%
45-54……… 24%
55-64……… 9%
65+……….. 4%
A back of the envelope calculation tells us that if we can get an additional 1.4 million Arizonans fully vaccinated in the coming weeks we’ll be able to hit the 50%+ mark (out of our total population of 7.2M).
But… nearly 1/2 of those 1.4M persons have received one dose of the vaccine. If we can complete the vaccination schedule for the 700,000 that have received one dose and get an additional 700,000 persons fully vaccinated, we could probably get to the herd immunity threshold.
What do we need to do to get there?
There are basically 4 groups that have yet to be vaccinated in AZ. Each require a unique strategy to achieve success.
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Persons that still lack access to vaccine because of their circumstances. This category includes folks that are juggling multiple jobs, lack reliable transportation, face language and other communication barriers.
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Persons with busy lives that want to get vaccinated (and face no economic or language barriers) but that won’t get vaccinated unless it is made very easy. This group also includes men that are willing to get vaccinated but aren’t motivated to make an appointment (men are vaccinated at far lower rates than women in Arizona).
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Persons that still have questions before they’re willing to get vaccinated. You can call these folks vaccine hesitant. They mostly want to have a conversation with someone they trust before deciding to get vaccinated.
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People that are unwilling to get vaccinated and are set in their position.
To get to herd immunity we need to adjust our vaccine strategy away from the mass-vaccination sites that require an appointment toward community-based locations. Here are some ideas for each category of yet to be vaccinated people:
For people in Category 1 we need higher touch community-based solutions. Mobile clinics in partnership with trusted organizations like churches, community centers, local nonprofits and the like. Flexibility is the name of the game here. It’s not rocket science, but it is more labor intensive.
Our county health departments are working hard via mobile and community based clinics to make inroads for this population. Continued creative engagement will continue to make progress here. More vaccine and resources still need to be moved away from the vacant state-financed and university-run sites toward counties.
For people in Category 2, we need to get rid of the appointment systems. This group wants spontaneous convenience. Hopefully, pharmacies and other locations will begin offering COVID vaccines without appointments.
Our county health departments and even the state-financed and university run mass vaccination sites have now largely gone to a no-appointment system- which will help a lot with Category 2 people.
Category 3 people are most likely to get vaccinated at their doctor’s office or clinic after a conversation with their nurse, nurse practitioner or doctor. Starting next week doctors that have already been on-boarded by the ADHS as a COVID vaccine provider can FINALLY order up to 200 doses of Moderna vaccine for their patients.
Governor Ducey & Director Christ’s Executive Order 2020-62 creates a regulatory barrier for doctor’s offices to get vaccine. That EO needs to be repealed and the ADHS needs a full-on effort to make it much easier for doctors and clinics to order vaccine in order to make progress with this population.
Category 4 people are a problem. Putting effort into this cohort is a bad return on investment at this point. Better to focus our resources on Category 1, 2, and 3 people.
As long as we implement the recommendations above, there’s a good chance we can achieve vaccination rates sufficient to greatly suppress transmission in all age groups and achieve herd immunity like Israel did. There will be plenty of vaccine… the question is whether the state’s strategy and execution will be effective enough.
Forecasting Exercise: To get to herd immunity (using Israel’s experience as the model) we’d need to finish vaccinating the 700,000 persons that still need their booster shot and then fully vaccinate an additional 700,000 persons. Put together, that’s an additional 2.1M vaccines to administer.
Last week about 250,000 vaccines were administered statewide. If we assume a steady pace at that rate (which is optimistic because we have seen a drop off in vaccines administered in the last few weeks), we could administer 2.1M doses in 8 weeks (and herd immunity) by the 4th of July.
However, if we assume that the persons that have received 1 dose are protected enough not to spread the virus, and that the new 700,000 new persons that need to be vaccinated once are vaccinated at a rate of about 125,000 per week (1/2 of the current weekly doses administered), we could achieve a goal of getting at least 50% of the adult population vaccinated with at least one dose (and herd immunity) by June 15.
