Are you excited about the Pfizer (available now!), Moderna (soon!), and other anti-COVID-19 vaccines that will be approved for “emergency use” to get us back to our lives… or are you skeptical? Maybe you oscillate between fantasies of mask-free parties and fears of Bell’s palsy or anaphylaxis. A large-scale vaccination program is coming to your town soon, and how you feel is less important than what you actually do.

Let’s begin with how you feel. Both the Pfizer and Moderna vaccines represent a feat of biochemical engineering that has excited virologists for years. Only now, with a dramatically feel-good cooperation between scientists, private and public funders, and an Operation Warp Speed elimination of bureaucratic delays, we have a teeny tiny mRNA sequence wrapped in lipid nanoparticles that is safe, effective, and already mass produced for shipment. But we’re wary of this new technology because it is… new.

Well, kind of new.

Scientists have been working on mRNA vaccines for many years. Dr. William Schaffner, an infectious disease expert from Vanderbilt University, reminds us that although these were produced quickly, the technology stands on the shoulders of 10-15 years of work and peer-reviewed data. Also, after reading the 53-page report to the FDA to approve emergency use authorization (EUA) of the Pfizer vaccine, Schaffner’s study group of experts “… arrived interested… and left enthusiastic” with no concerns about safety.

A quickie review of how these mRNA vaccines work may minimize fear of the unknown. Wrapped in its lipid coat, a small section of the SARS-CoV-2 genome coding for its spike protein enters your cell and uses its machinery to make and display it. Your body says, “OOH! Weird protein! Better make an antibody and tell everyone else something is going on.” That little bit of mRNA has no ability to incorporate into your own DNA and is easily degraded (which is why it needs the “cold chain” from the lab to your doctor’s office to protect it). After two vaccine doses, your body is more likely to recognize COVID-19 quickly and mark it for destruction. It is important to understand that the vaccine won’t prevent you from becoming infected, but will significantly reduce the chance that you’ll even know it. Those that do get sick are less likely to need to be hospitalized; and those sick enough to go to the ER are far less likely to end up in the ICU. We predict that fewer coughing, feverish people will also drop the transmission rate, but we don’t really know that. So you’ll need to hold onto those masks for a while. Like, another year.

With these assurances, Dr. Fauci’s endorsement, and the heart-warming trio of Bush/Clinton/Obama willing to bare their deltoids in the name of public health, why do we still feel uneasy? It’s too easy to blame the outgoing administration for poor leadership. None of us particularly likes shots. Even though side effects are minimal and true vaccine injuries rare, the risk is never zero. It is encouraging that the vast majority of us here in Massachusetts got our flu shots when they were mandated. We clench our teeth and kiss our babies when office visits require them to be pricked so many times in their first two years. In spite of our gut reaction to a not-zero risk of vaccines, we do what we’re asked to protect our families and others. Many of us are a little vaccine-hesitant, but most of us demonstrate pro-vaccine behavior.

In 2014, a devastating measles outbreak that started in Disneyland and crossed borders to Canada and Mexico was traced back to an “under-immunized” population. Instead of uncovering a health-care desert where low-income communities faced obstacles to receiving vaccines, epidemiologists exposed a privileged set of people who erroneously believed their quintessentially healthy California lifestyle (homeschooling, vegan, organic, etc.) exempted them from needing them. Fearful of side effects and overconfident in their immune systems to beat deadly diseases, a tipping point of people claimed a personal or religious right to refuse recommended shots, and herd immunity failed. The only path to restoring it was to eliminate personal belief exemptions for recommended vaccines, which California did only a few months later.

Nearly a year into the COVID-19 pandemic, herd immunity has crept into our everyday conversations. Raise your hand if you’ve discussed the Rnaught (R₀) of SARS-CoV-2 in the grocery line! Ok, maybe that’s just me. But it’s an important bit of math to consider as we move forward. R₀ is the coefficient of infectivity, or the number of susceptible people who will get infected by ONE contagious person. Mathematical models can predict a threshold percentage of immune (or immunized) people needed to achieve herd immunity:

(R₀ – 1) / R₀

For measles, with a R₀ that can reach 20, when the percentage of vaccinated people dips below 96%, herd immunity is lost and just one virus-shedding kid at Disneyland sends measles across North America. 

For COVID-19, the R₀ in most studies hovers around 2-3, but has been reported close to 7. It is wildly important for everyone to realize that this is not a reflection of a mutable disease. The R₀ is a dynamic variable because it changes with our BEHAVIOR. You can look at the data in your own state or town and see the effect of social distancing, mask mandates, and travel restrictions on R₀ (or the R_T, the coefficient of transmission, which is similar).

Our curve-flattening behavior in the late spring drove the R₀ so low, many of us enjoyed low-capacity indoor dining. The athletic club my father was forced to sell in April was able to reopen with a new owner in July. Most of our kids have returned to synchronous, in-person learning at least a few days a week. But then the spikes, surges, second and third waves, super-spreader events, and Thanksgiving happened. How does this relate to vaccines on the horizon? Our ability to control the R₀ impacts how well they’ll work.

A pretend and overly simplified example is that if the R₀ is 5 when a vaccine is deployed in an unimmunized population, we would need (5 – 1)/ 5 or 80% of us to receive our second doses before herd immunity takes effect. However, if masking and social distancing keeps the R₀ hovering around 2, we’ll achieve herd immunity after only half of us are vaccinated. This is why it is so important to keep our guard up now. This is why you were asked to restrict Thanksgiving gatherings to your “bubble” and why you really need to reconsider Christmas plans that ignore guidelines.

So what are you going to do? Front line workers are going to need to figure this out for themselves rather soon, as vaccine delivery to 145 sites across all 50 states begins Monday. Our elderly citizens (or their children who make medical decisions for them) should already have a plan of action lest they lose an opportunity to take advantage of limited supplies. With only EUA approval (and only for those over 16 years old), a mandate is something for classroom debates and, ahem, blogs. The choice is yours. What will you do?

I hope you will devour all of the good information you can find from reputable sources. Ask questions. Query your friendly neighborhood epidemiologist or someone who has treated COVID-19 patients. Know how these mRNA vaccines work and the real data behind side effects. Remember that a vaccine deployed to billions of people will yield reports of temporally associated events that have nothing to do with the shots. Every medical student knows the cautionary tale of the baby that had his first grand mal seizure in the doctor’s office mere moments before his first doses of standard vaccines. What would we assume if the seizure had happened afterward? 

Is it too much to ask that all of us take a brand new vaccine? I think we’ll all need to manage our uneasiness. But just because the vaccines are “new,” doesn’t mean they are “untested.” Over 70,000 people were enrolled in the studies for these two mRNA vaccines. Doctors who don a white coat and swear to “first, do no harm” are also going to take it before you do. 

A time will come when we might be thrown into pro- and anti-vaccine camps, but that is unfair and unhelpful right now. However, if you find yourself relying on your own good health or relative youth to brave the actual disease over the negligible risks of a new vaccine, think about the rest of us, too. This pandemic has revealed that our health care system has already failed those in low income communities, people who live in close quarters in multi-generational homes, and those who do not have the luxury of working from home and are reliant on public transportation. When you take the vaccine, you are helping to protect them from a more severe course of the disease, too. Also, when you say, “if I get it, I’ll be fine” are you in the same mindset as the kale-chomping Californians who brought unvaccinated children to Disneyland? I agree it’s a bit more nuanced debate to consider taking a brand new vaccine, but the fact remains that doses are arriving to your town soon. Will you be a part of history or will you wait and see?

What will you do?