These new RNA vaccines are a triumph for science and medicine

This week the FDA approved a second vaccine against SARS-CoV-2, the virus that causes Covid-19. We now have two highly effective vaccines, one from BioNTech and Pfizer, and the other from Moderna. A third vaccine, from Oxford University and AstraZeneca, is very close to approval.

The two new vaccines, both based on RNA, are both remarkably effective. Below I’ll summarize some of the numbers, which have been published for the world to see.

This is a scientific triumph. Less than a year ago, no one outside China even knew this virus existed. The genome of the virus was first released in January, and within a few months scientists had designed the first vaccines. Clinical trials were launched immediately, and larger trials followed, leading us to where we are today: two new vaccines, tested and validated in tens of thousands of people, now being manufactured and shipped to billions.

For anyone who might be skeptical, or who just might want to know more, the test results are being published openly. The New England Journal of Medicine has a dedicated website with dozens of papers and audio summaries, including results from the large-scale (Phase 3) trials of the Pfizer vaccine.

Before getting into the numbers, let’s summarize what these two new vaccines are. (I wrote about this in July, if you want to read my previous explanation.) Both of them are RNA vaccines, which is itself a dramatic breakthrough. RNA vaccines have been discussed for years, but the technology was never employed for human vaccines until now.

Here’s how they work: our immune system (which is super-complicated, as Ed Yong explained in The Atlantic) recognizes microscopic invaders and destroys them. Once you’ve been infected with Covid-19, the immune system swarms over the viral particles and basically learns what they look like. SARS-CoV-2 has a protein all over its surface called “Spike,” so that’s what the immune system recognizes.

Once you’ve fought off the infection, the immune system remembers what Spike looks like. If you’re infected again, it can respond far more quickly, so you won’t get sick. This is what we call acquired immunity.

So for vaccines, the trick is to teach your immune system to recognize Spike. One way to do that is to manufacture lots and lots of the Spike protein, and put that in the vaccine (sort of–I’m greatly oversimplifying here).

But with modern genomics technology, we can use a different approach. Every cell in your body has machinery inside it to translate RNA into proteins. As soon as we had the SARS-CoV-2 genome, back in January, we knew the genetic code for Spike. So rather than make the protein, what if you just made the RNA, which is far easier and faster to manufacture, and injected that into people? Do our own cells then translate the RNA and make the Spike protein?

Well yes, they do. And not only that, but–as the Modern and Pfizer clinical trials have now proven–our immune system recognizes that the Spike protein is foreign (it’s complicated) and launches an attack.

So to make an effective RNA vaccine, you simply have to inject enough RNA so that the immune system responds. That’s what both the Modern and BioNTech/Pfizer vaccines have done.

Now let’s look at the numbers. As reported in NEJM just two weeks ago, the Phase 3 trail for the Pfizer vaccine tested 43,448 volunteers, of whom 21,720 got the vaccine and 21,728 got a placebo. At the time of the report, 162 people who received the placebo had become sick with Covid-19, but only 8 people in the vaccine group got sick. That’s a 95% reduction in illness, a remarkably good result. They also reported that 10 people had “severe” illness, and 9 of those ten were in the placebo group.

How about the Moderna vaccine? This vaccine has almost identical efficacy, published in a preliminary report a few weeks ago as 94.5%. Just a few days ago, an FDA review panel approved the vaccine and confirmed that its efficacy was above 94%. And the Modern vaccine doesn’t need the super-cold freezers that the Pfizer vaccine needs, which makes it easier to distribute.

Both vaccines have minimal side effects in most people, mostly soreness at the injection site, and sometimes headaches or chills, which subside within a day. RNA is quickly degraded in the body, so there’s no reason to expect any lingering side effects from these vaccines.

There’s also growing evidence that immunity lasts for many months, if not years. Another report in NEJM, on the Moderna vaccine, contains some of the latest data, which shows that immunity is still strong after 4 months. Of course, with a brand-new vaccine, we simply have to wait to see if the immunity lasts for years, but all signs are positive right now.

So yes, these are really good vaccines. I will get mine as soon as I can, although I expect I’ll have to wait several months because of short supply.

(The Oxford/AstraZeneca vaccine, a more traditional protein-based vaccine, has also shown positive results, either 62% or 90%, depending on the dosage regimen, but the 90% results are based on fewer cases. Even so, it is clearly effective and it should be approved soon, at least in the UK. So we might soon have 3 vaccines.)

A note to anti-vaxxers: no, you cannot catch Covid-19 from these vaccines. They don’t contain the virus! They only have a fragment of RNA from one protein, and the virus has RNA that encodes 28 other proteins. It’s simply impossible for the virus to self-assemble without the rest of its genome.

But hey, if you don’t want the vaccine, go to the back of the line. Most of the world is desperate for it.

The success of RNA vaccines is a huge win for science, but even more, it’s a huge win for the human population. We’re still many months away from vaccinating the whole world, but with two highly effective vaccines, we can finally have hope to end this pandemic.

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