We are in a race against time. SARS-CoV-2 is evolving, as viruses do, creating thousands of strains as the virus continues to move through the human population. Epidemics and pandemics are great opportunities for viruses to evolve. Most of the strains identified are behaviorally roughly identical to the original strain, but a few have now been identified that are better at transmitting themselves from host to host. These strains are quickly dominating.

The UK strain known as B.1.1.7 rapidly spreads through countries where it gets introduced. It has been found in the US and epidemiologists predict that by late March it will dominate and we will likely see a new COVID-19 surge. There is also a Brazil variant and a South African variant. All three variants share some mutations on their spike proteins, although they appear to have emerged independently. While they spread more easily, none appear to be more deadly. The South African variant, however, may be resistant to existing vaccines.

This is a major problem of allowing viral pandemics to simmer – eventually new strains will emerge that are more infectious, more deadly, or resistant to treatments or vaccines.

On the other hand, we now have several effective vaccines. Over 42 million doses have been distributed in the US, almost 10% of the population. A massive vaccination program is under way, with a goal of 1 million doses given per day. However, some experts feel the goal should be more like 2 million per day, if not more. This is the race – can we get to herd immunity before we get another surge (and we’re still not over the last surge) from a new and more infectious strain?

Herd immunity (or “community immunity” as some prefer, but I fear we are stuck with the herd) is achieved when enough people are immune to infection that an infecting organism cannot find enough receptive hosts to perpetuate itself through a population. In other words – it cannot spread, and so the infection burns itself out. If you maintain herd immunity long enough you may even eliminate the organism so that it is no longer endemic in a population (although there still may be outbreaks if reintroduced from other populations). If there are no non-human reservoirs, a disease may in fact be eradicated completely, like smallpox and (hopefully) polio soon as well.

Coronaviruses have non-human reservoirs, so we will have to live with them, but aggressive herd immunity can prevent epidemics and pandemics. The only way to get there is through a successful vaccination program. Unfortunately, the initial rollout in the US was underwhelming, and we lost precious time.

Now that the logistics of the vaccine program seem to be on track, the other variable in this race is how receptive the population will be to the vaccines. In a recent survey vaccine hesitancy was high:

COVID-19 vaccination intentions were weak, with 14.8% of respondents being unlikely to get vaccinated and another 23.0% unsure.

That means only 62% said they were likely to get the vaccine. We don’t know for sure where the herd immunity level will be, but something around 85% is a good guess. It could be higher. This means we have to convince essentially everyone in the “unsure” group to get vaccinated, assuming the “unlikely” group are more anti-vaxxers than merely vaccine hesitant.

Factors that influence vaccine acceptance include:

In a multiple linear regression, significant predictors of vaccination intent were general vaccine knowledge (β = 0.311, p < .001), rejection of vaccine conspiracies (β = −0.117, p = .003), perceived severity of COVID-19 (β = 0.273, p < .001).

Other favorable factors include being male, income > $120k, being a Democrat, and not watching Fox News or relying on social media for information. Of note, this survey was in the English speaking population only, and there is evidence that the Hispanic population has greater vaccine hesitancy due to a lack of trust in the government.

These numbers are also similar worldwide.

I have encountered vaccine hesitancy among my own patients, and they are mainly based in fear spawned by rumors they “heard somewhere”. One patient worryingly reported that they heard “someone died three weeks after getting the vaccine”. Given that over 42 million people (mostly elderly) have been vaccinated, that is a statistical certainty. But there are no deaths attributed to either COVID vaccine. Reviews of deaths occurring shortly after a vaccine dose find the numbers are consistent with the background number of all-cause mortality. Further, no individual case seems to be related to the vaccine.

But it is far easier to scare people with anecdotes than to reassure them with data. This is why the anti-vaxxers have an easy task – they do not have to produce compelling data or even a cogent argument. They can spew abject nonsense. All they have to do is generate unreasonable fear through rumor and innuendo.

There is a light in the survey data, however. General vaccine knowledge did predict vaccine acceptance. It may be true that vaccine knowledge may simply be a marker for other things, like scientific knowledge in general, trust in institutions, or using reliable sources of information. But it also seems likely that it is an independent factor related to vaccine uptake. That’s good news because this is a modifiable factor, improved through education. This is the “knowledge deficit model”, which likely does not apply to conspiracy-theorist anti-vaxxers, but may apply to the misinformed vaccine hesitant. Hopefully that is the only group we need to get to herd immunity.

Therefore, as part of the massive vaccine distribution effort underway, we need an equally massive vaccine education effort. That could be the margin of victory in this race against emerging SARS-CoV-2 variants.

We also need to keep in mind that worse is likely to come. There will be further new strains of SARS-CoV-2. There will be new viruses and at some point we will face the next pandemic. A rapid and effective vaccine program is our best defense. This makes not only education but fighting anti-vaxxers, and more generally countering conspiracy theories and anti-science, critically important.


Posted by Steven Novella

Founder and currently Executive Editor of Science-Based Medicine Steven Novella, MD is an academic clinical neurologist at the Yale University School of Medicine. He is also the host and producer of the popular weekly science podcast, The Skeptics’ Guide to the Universe, and the author of the NeuroLogicaBlog, a daily blog that covers news and issues in neuroscience, but also general science, scientific skepticism, philosophy of science, critical thinking, and the intersection of science with the media and society. Dr. Novella also has produced two courses with The Great Courses, and published a book on critical thinking - also called The Skeptics Guide to the Universe.