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The best way to avoid future variants is to vaccinate the world

The delta variant makes it clear: Vaccinating the world is in America’s best interests.

People stand in a line outside a vaccination clinic in India.
Residents in Mumbai line up for Covid-19 vaccinations, which are still scarce in most of the world.
Pratik Chorge/Hindustan Times via Getty Images

The delta variant has changed the fight against Covid-19 in the United States. Before it became widespread, cases were on a pronounced downswing, especially in high-vaccination parts of the country. It was starting to look as though most vaccinated people might be able to forget all about Covid-19 and return to their lives.

Now, cases have spiked even in highly vaccinated areas, the CDC has recommended a return to masking indoors even for vaccinated people, and the day when Americans can stop thinking about Covid-19 looks as distant as ever.

That’s bad enough. America’s global health policy is setting the country up for worse.

In low-income countries, only 1 percent of people have received a vaccine dose, and access to the mRNA vaccines that work best against delta is basically nonexistent. Covax, the international effort to provide vaccines to nations in need, has struggled because of funding and supply issues. The failure to vaccinate the world can shape up to be the foundation of an even worse turn in the pandemic: the emergence of a new variant that’s more infectious and possibly even deadlier.

New variants of the coronavirus can arise whenever the virus has the chance to infect people and multiply in the human body. The reassuring news is that while viruses mutate constantly, most of those mutations are meaningless and not harmful. But if you roll the dice enough — if you give a virus enough chances — the virus could take on mutations that worsen Covid-19.

With a global health policy that hasn’t prioritized vaccination enough, the world is rolling the dice repeatedly. It doesn’t need to be that way. Vaccinating the whole world is achievable and even affordable. One estimate puts the total cost at $50 billion to $70 billion — a pittance compared to the toll of a new surge. Such a global campaign would dramatically reduce the odds of new variants arriving.

The US failure to take leadership on that front isn’t just a humanitarian and moral failure. As delta shows, it’s also incredibly short-sighted and terrible for America’s own health security.

Variants, explained

To understand why vaccinating as many people as possible is essential to preventing new and deadlier variants, it might be worth explaining briefly how variants come about.

When a virus infects someone, it forces their cells to make billions of copies of the RNA that makes up its genetic code. For Covid-19, it’s estimated that an infected person’s body can ultimately produce between 1 billion and 100 billion copies of the coronavirus.

Now, the copying process isn’t quite perfect, and almost all of those billions of copies will be different from their parent virus in a few small details.

Most of the time, those differences — introduced by copying errors — will have no effect, or make the virus less effective at infecting people. A metaphor might help explain why: Imagine that you have a book. Most possible random letter transpositions will make the book worse. A letter transposition that makes the book better would be exceptionally rare.

Most possible changes to Covid-19’s RNA are probably bad for the virus with the mutation, or simply irrelevant. Early in the pandemic, there was a lot of panic over variants that turned out to be relatively harmless — not particularly different from the original SARS-CoV-2.

Eventually, though, an unlucky roll might produce some random changes to Covid-19’s genome that could make it more transmissible, more virulent, or more able to evade the immune protections offered by vaccines.

“By keeping cases so high, you increase the chance that sooner or later, you’re going to hit that jackpot,” molecular epidemiologist Emma Hodcroft told my colleague Brian Resnick. “We keep rolling the die when we keep the cases up so high.”

The unlucky “jackpot” so far is delta. It appears to be better at latching onto human cells, and it’s far more transmissible. There is also some preliminary evidence that delta is better at evading the immune response, so it can more easily infect people who’ve already experienced Covid-19.

Once that random change happened, the viruses with that lucky advantage were able to out-reproduce the viruses that didn’t have it. The delta variant started out as just one random mutation in a single Covid-19 patient. Now, most new Covid-19 cases in the US are estimated to be delta, and it’s been detected in 98 countries.

Delta’s bad. It could be worse.

“The scary scenario is that this is not the last or the most harmful variant,” Maureen Miller, an infectious disease epidemiologist at Columbia University, told Vox.

There are in fact a lot of ways things can get worse.

First of all, future variants could get even more transmissible. “This virus has surprised us a lot,” Aris Katzourakis, a virologist at the University of Oxford, told the BBC. “The fact it has happened twice in 18 months, two lineages (alpha and then delta) each 50 percent more transmissible is a phenomenal amount of change.” And while he said it’s “foolish” to try to estimate how much more transmissible Covid-19 could get, he says we could see future large jumps in transmission.

“There is still space for it to move higher,” Wendy Barclay, a virologist at Imperial College London, told the BBC. The R0 of the coronavirus — a measure of how many people a single infected case will infect in a population without immunity — was estimated at 2-3 for the original SARS-CoV-2 virus. Delta might have an R0 as high as 8.

“Measles is between 14 and 30,” Barclay added. Measles, though, is an extraordinary outlier among diseases in infectiousness. But delta is starting to get into outlier territory itself, and it’s worth at least pausing to consider what future more transmissible variants might be like.

What would it be like if a future variant of the coronavirus were as bad as measles? According to the CDC, measles is so infectious that the virus can live in an airspace, infecting new people, for up to two hours after an infected person leaves. If a person is infected, up to 90 percent of their close contacts will also become infected (assuming none of them are immune). And infected people can spread measles to others up to four days before symptoms appear, making contact tracing nearly impossible.

There’s another thing that could get worse. Existing mRNA vaccines work quite well against delta. They’re not perfect, but they seem to dramatically reduce odds of transmitting Covid-19 onward (current estimates suggest an efficacy rate of 80-90 percent against infection), as well as the risk of hospitalization and death. Most of their benefits have held up against every variant so far, even as other vaccines have proven much less effective.

Vaccination, then, is our best tool to fight the virus. But if rich countries dawdle too much, it is possible that eventually a variant could arise that blunts that tool. “The emergence of future variants that can escape vaccine-induced immunity” is a possibility, former CDC Director Tom Frieden has argued.

The mRNA vaccines, in particular, seem to induce a very strong, robust immune response in multiple parts of the immune system. Many virologists have argued it’s unlikely a virus could escape that while remaining highly transmissible. But with trillions of rolls of the dice, it’s possible that the virus will stumble on a way to evade our immune response.

“Continued uncontrolled spread around the world makes this scenario more likely,” Frieden says.

How vaccinating the world can stop future variants from emerging

In high-income countries, on average, 51 percent of people have been vaccinated. In low-income countries, only 1.36 percent have.

The humanitarian case for vaccinating the world is very clear: Social distancing and masking appear to often be insufficient to contain the delta variant, so even countries that had successfully avoided Covid-19 up until this point are now getting slammed. New waves are crushing countries such as Indonesia, South Africa, and Malaysia.

According to official estimates, 4 million people worldwide are known to be dead from Covid-19. But measurements of excess deaths tell a story of a toll that’s even worse. One recent estimate found that approximately 4 million to 5 million people have died of Covid-19 in India alone — most of them in the last month and a half as delta swept the country.

Vaccines would save millions of lives, both directly, by protecting people from serious cases of Covid-19, and indirectly, by making it harder for the virus to spread.

But the vaccines that work best against delta are the mRNA ones, which are more difficult to manufacture compared to other vaccines like AstraZeneca’s or Sinopharm’s, which are available outside the US.

So far, the rich world has been reluctant to take even small steps to ensure universal access to vaccines. The Biden administration has pushed for waiving intellectual property rights to the vaccines, but other countries have pushed back, and experts say that even if rights are waived, it won’t change much.

“Waiving vaccine patents is fine, but unless it’s tied to a process that actually increases the supply of vaccines, it’s little more than expressing thoughts and prayers after a tragedy,” sociologist and Covid-19 commentator Zeynep Tufekci wrote in May, urging governments to do much more to actually vaccinate the world.

What’s really needed is funding, massive preorders for the doses needed to vaccinate the world, and a concerted effort to ensure those doses reach everyone in the world. Building the factories to pump out vaccines on that scale will help the world with the next pandemic, too.

If saving millions of lives worldwide is insufficient motivation for the US to do that, maybe the case from self-interest will be stronger. Already, delta is delaying the return to normalcy that Americans long for — and killing thousands of people. The world cannot afford another variant that could be even worse.

Compared to that, the $50 billion to $70 billion needed to vaccinate the world starts to look downright cheap. That’s a bargain just because of its benefits in saving human lives; it’s even more so because it will help prevent future variants from arising.

The rise of delta after such a promising spring in the US underscores a fact many Americans may have forgotten amid the good vaccine news at home: This is still very much a global crisis that Americans are not exempt from. The US should act accordingly.