In a world of variants, vaccine hesitancy is the key hurdle
The US will struggle to achieve herd immunity
The US vaccine effort has galloped ahead thus far with 38% of the population receiving at least 1 dose (see Bloomberg’s vaccine tracker). But we are fast running out of those most eager to be vaccinated. A recent poll on vaccine hesitancy shows only 47% of Americans are committed to being vaccinated:
The US is giving first shots to 4-5% of it’s population per week right now. It need only vaccinate about 10% more to hit a point where vaccine hesitancy begins. That will be two weeks or so from now.
Hesitancy is not just a US issue. Israel is a real-world example of how the vaccine hesitancy problem bends the curve:
As the chart shows, Israel’s vaccination rate slowed markedly after dosing 55% of its population. (The UK has also seen a slowdown, but that is due to supply issues).
The problem in Israel however is vaccine hesitancy. As per the Times of Israel:
While early in the inoculation drive there were long lines of people trying to get standby appointments at vaccination centers, now healthcare providers are trying to convince people to take shots. “We’re being proactive, calling people, asking them to come for vaccination, and reassuring them,” said Mali Kusha, chief nursing officer at Meuhedet Health Services.
The US has some mitigating factors. One, among adults over 65 years old, 80% are already vaccinated according to the CDC, which means the fatality rate will keep going down. Two, many Americans have some immunity from natural infection which needs to be factored in. There is considerable debate as to their numbers but Youyang Gu’s covid-projections.com estimates 30% or so of the US population has already been infected. My crosschecks incline me to believe that.
Once 50% of Americans are dosed and the effort slows down, where will we stand vis-à-vis herd immunity? If we include the 30% with protection from natural infection, and account for the overlap between the two, we get that the number of “protected” US residents will be ~ 30% + (1-0.3) * 50% = 65%. That sounds very good until one realizes that “protection from covid” has more than one meaning. Vaccination is excellent at protecting people from death, 99.7% as per this estimate, but not as good at preventing transmission of the virus itself. To stop transmission you need “sterilizing immunity” which is a higher bar to cross. Here’s what recent research says about rates of sterilizing immunity:
Thus vaccinations do leave a window open for transmission. A meaningful 15% or so of those vaccinated or naturally infected can still spread the virus though they may not fall sick from it.
Therefore 65% of the population with protection translates into a lower number with sterilizing immunity i.e. about 0.85 * 65% ~ 55%. That’s not nearly enough to achieve herd immunity esp. given the new variants. The original virus had a reproductive number R = 2.5 which placed the herd immunity threshold at (1-1/R) = 60%. Achievable. But the more infectious variants such as B.1.1.7 have a 40% higher infectiousness, placing R at 3.5 or so. This would require sterilizing immunity of 70-75% which in turn needs 80-90% of the population to be protected through vaccination or infection1, a much more difficult goal.
Thusly, the tempo of the covid-19 epidemic will reduce and fatalities will go down but it is unlikely that the US will defeat covid-19 this summer, despite its enormous vaccine resources. Some fatalities will continue, mainly among the vaccine-hesitant and people with compromising immune conditions.
Having said that, I do think the US will achieve a level of normalcy soon because business restrictions will fade once eliminating2 the risk of death becomes a personal choice of getting a jab at a local CVS. But even so, some people will still restrict their activities due to the continuing background of fatalities and cases. This should cause some drag on economic activity. I still see a strong recovery in the US, but probably more incremental than the “big bang” that many observers have been expecting.
To end this discussion, people should think beyond the US optimism as the global situation is much more dire. Vaccine supplies are rising in the EU but they will not have the same availability as the US for a few more months. To add to that, it is not as if the EU has lower levels of vaccine hesitancy - if anything some countries like France have a larger contingent of anti-vaxxers (see table on top). Meanwhile, there are problems with AstraZeneca and the Chinese vaccines which were expected to be the workhorses of the global vaccination effort. AstraZeneca’s supply is constrained because its largest production center, India, is facing a double whammy of an explosion in covid cases and US restrictions on supply of vaccine raw materials. Meanwhile, the word is out that the Chinese vaccines are not very effective. The head of China’s CDC, Dr. Gao Fu, admitted this the other day before retracting, perhaps after the CPC leadership had a talk with him.
There’s much to think about here at the global level and it’s very sobering.
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Also using the 85% average efficacy against transmission here
Unfortunately, this does leave out people who may not get the desired results from vaccination due to immune disorders or just plain bad luck.