Why you should trust the coronavirus vaccine

Let me start by making one thing clear: at the time of this writing, we don't have a scientifically validated vaccine for COVID-19. But more than 150 vaccines are being developed around the world, and many of them are already in advanced stages of testing.

So we'll have a vaccine soon, likely in a matter of months. And everyone should take it. I know I will.

Today I’m going to try to de-mystify vaccines a bit, in the hope that this might help people feel more comfortable with them.

Before explaining what a vaccine actually is, let me point out that vaccines are probably the single greatest medical advance in the history of human civilization. Vaccines have saved hundreds of millions of lives: prior to vaccines, people lived in fear of diseases like smallpox, which killed 300 million people in the 20th century alone. Thanks to the vaccine, we eradicated smallpox from the entire world in 1980. Polio is another dreaded disease that killed or permanently injured millions, until the 1950s, when Hilary Koprowski, Jonas Salk, and Alfred Sabin invented vaccines that protected against it. Today, no one in the U.S. or Europe worries about polio, and it too has nearly been eradicated worldwide.

What exactly is a vaccine? It’s a pretty simple concept. Our immune system has the remarkable ability to “remember” pathogens that we’ve been exposed to. So once you’ve been infected with some viruses or bacteria, you acquire immunity to those diseases that may last the rest of your life. A vaccine is basically a way to teach the immune system to recognize a pathogen without actually making you sick.

The simplest way to do this (conceptually) is to take a batch of viruses or bacteria, kill them so they’re harmless, and then just inject them into a person. The immune system then “sees” the proteins in the dead pathogens (because the proteins are still floating around), and it learns all it needs to know from these. Later on, if a live virus infects that person, her immune system will say “aha, I know you!” and will quickly surround and destroy the invaders.

Simple as it sounds, there are many complications with this process. One is that it’s often very hard to isolate and grow enough of the virus (or bacteria) for large-scale production. The viruses then need to be isolated, killed, and purified, which can be complicated and costly. For COVID-19, though, any cost is worth it.

Another, much newer way to make vaccines uses modern molecular technology to make RNA. There’s no need to isolate or grow the virus at all! This is how Moderna’s new mRNA vaccine works (see their whitepaper here).

The mRNA vaccine relies on the fact that we already know which protein in the SARS-CoV-2 virus is the most important one. It’s called the spike protein, so I’ll just call it Spike. Spike is what attaches to human cells and lets the virus infect them. We also know the sequence of the Spike gene: the sequence of the entire SARS-CoV-2 virus was released in early January, and we’ve now sequenced thousands of these viruses.

An mRNA vaccine simply uses the RNA itself, rather than dead viruses. Today we can synthesize RNA in large quantities, so if you take some of this RNA and inject it into a person, what happens? Well, our own cells will translate this RNA to produce the Spike protein. All by itself, the protein cannot possibly cause an infection. It’s analogous to having a motor without a car: you can’t go anywhere without the whole package.

But here’s the good part: our immune system will recognize Spike anyway, even without the virus, and it will remember this invader. So the RNA vaccine is, in theory at least, even safer than traditional vaccines, because live pathogens are never used in the production process. (Before the anti-vaxxers jump on me here, let me emphasize that traditional vaccines are incredibly safe.)

This is just one example: there are 23 vaccines already in human trials, and over 150 in development, using mRNA, proteins, and other approaches.

There are other ingredients in vaccines too: preservatives and adjuvants. Anti-vaxxers like to read vaccine ingredients and then claim that all sorts of harmful stuff is in there, but their claims are mostly just gross ignorance. Preservatives are there to prevent the growth of things like bacteria, so they make vaccines safer. And adjuvants like aluminum salts (the most common adjuvant) are ingredients that enhance the effectiveness of vaccines, meaning you can use a lower dose. Aluminum salts have a very long safety record.

So why don’t people trust vaccines? Largely because the anti-vaccine movement has spent years spreading misinformation and fear, and it is already pronouncing strong opposition to any coronavirus vaccine, regardless of the evidence. The New York Times reported this week that mistrust of future coronavirus vaccines could imperil public health, especially in the United States. Polls have shown that large proportions of Americans say they won't take a vaccine even when it's available, which is, frankly, kind of crazy. (It didn’t help when tennis player Novak Djokovic expressed doubts about whether he’d be willing to take any future coronavirus vaccine.) Last month, NIH’s Anthony Fauci said that the “general anti-science, anti-authority, anti-vaccine feeling” in the U.S. may seriously undermine the effectiveness of any future vaccine. Of course, this could change once we really do have a vaccine, and we should all hope it does. But the anti-vaxxers never let up.

It also doesn't help build trust when the Trump administration calls their vaccine program "Operation Warp Speed." This might have sounded exciting to some sci-fi fans in the White House, but to many people it sounds more like a devil-may-care approach that emphasizes speed over safety. 

So how do we establish trust in the new vaccines, which are probably coming just a few months from now? One way to reassure people is to publish all the numbers from the vaccine trials. A just-published study in NEJM on the Moderna vaccine (the RNA vaccine) provides exactly these numbers, and they look very good in terms of both safety and effectiveness. 

In that study, all 45 participants had a robust antibody response–a stronger response, in fact, than in many people who’d been infected with the virus itself. There were some side effects, including fever and chills, but all were graded as mild or moderate. The scientists looked at 3 different dosage levels, and the side effects were greatest in the highest dose–but the antibody response was perfectly adequate in the lower dosage levels. So the next phase of testing, already under way, is using the lower dosages.

This was a phase 1 study, but it's very encouraging. If these results hold up in a large group–a question that is being tested now, in a phase 3 study–we'll have a working vaccine. 

And if you want to know more about this trial, you can read about it at the public NIH site, ClinicalTrials.gov.

Many if not all of the vaccines being developed in Europe and the U.S. are going through the same kind of scrutiny, and we’ll be able to see the results of those tests too. This is how we generate trust in the results: share them openly. I’m very re-assured by what I’ve seen so far.

The bottom line: vaccines work, and our methods for testing them are rigorous and thorough. With a little luck, the world will have multiple COVID-19 vaccines by the end of 2020. Once we have enough people vaccinated, our long nightmare with the coronavirus pandemic will come to an end.