This week, the Centers for Disease Control and Prevention issued new guidance on masking for those fully vaccinated against covid-19, recommending that people living in areas of high transmission once again don masks while inside public spaces. The move came after the CDC obtained new data concerning the Delta variant, the most transmissible strain of the coronavirus to emerge yet—data that suggests even vaccinated individuals who develop breakthrough infections can still transmit the virus to others.
All of these recent developments can’t help but bring to mind an important question: Is there now any chance of containing covid-19 before it reaches nearly every person in the world? And if not, how should we live with that reality?
Some of the data that informed the CDC’s new guidance was released to the public just this afternoon. But last night, the Washington Post reported on leaked internal documents from the CDC discussing it. Based on this data, which includes information from a recent outbreak among both vaccinated and unvaccinated people in Massachusetts, the CDC has determined that Delta is not only far more transmissible than the original strains of the coronavirus that widely spread last year—it’s also more transmissible than other notoriously contagious diseases, like chickenpox. People vaccinated with either mRNA vaccine (Pfizer or Moderna) still appear to have substantial protection against illness from Delta (around 80%) and very high protection against severe illness (upwards of 90%). But the CDC now suspects that vaccinated people who do become infected can produce as much of the coronavirus as those who are unvaccinated. If so, that would indicate that, if they do get infected, they can spread it to others. Importantly, they’re still less likely than unvaccinated people to spread the virus overall, since they have protection from infection in the first place.
These conclusions aren’t necessarily set in stone. Other countries, like the UK, have estimated a lower range of the reproduction number for Delta (also known as R0) than the CDC has. Some scientists have already questioned whether the CDC’s confidence about the potential for transmission from vaccinated people, based on results from PCR testing, is overstated. And the key point to reemphasize is that vaccinated people are still far better off than the unvaccinated across every metric—even the risk of getting infected at all from Delta appears to be eightfold lower, according to the CDC’s analysis, while the risk of serious illness and death is even more reduced.
But the emergence of Delta and other worrying variants had already made many scientists skeptical that it’s possible to put the genie back in the bottle, so to speak.
Even dating back to late last year, when the first vaccines were being released to the public, researchers with the World Health Organization leading the current pandemic effort warned that vaccination alone wasn’t likely to lead to covid-19's eradication. And just this week, U.S. government scientists reported that a third of white-tailed deer in several states were found to have antibodies to the virus, suggesting past exposure. While this discovery isn’t necessarily worrying (the deer didn’t appear to get sick from their exposure), it does probably mean that the coronavirus will have plenty of ways to continue circulating in the world.
In a survey of more than 100 immunologists, infectious-disease researchers, and virologists working on the coronavirus taken by Nature in February 2021, nearly 90% agreed that it was likely or very likely that covid-19 would become an endemic disease, meaning a disease that is always present at some level within a population. And while there are still groups dedicated to the idea of Zero Covid—the elimination of cases within a given area—more scientists have become vocal about their belief that covid-19 will inevitably remain a regular cause of human disease, like many other infections that have become endemic, such as influenza and common cold viruses.
The devil is in the details, of course. Just because a disease is endemic, that doesn’t mean it’s not serious. Malaria is endemic throughout the tropical parts of the world and remains one of the biggest killers of humanity, with more than 430,000 deaths reported worldwide in 2017. That said, despite the lack of a vaccine (for now, at least), we’ve been able to reduce the spread and deadliness of malaria in recent years, through dedicated insect control and treatment programs. Other endemic and highly contagious diseases, including chickenpox, have also become far less common in the U.S., thanks to high vaccination rates. And ideally, that’s still possible with covid-19.
A world where most people are vaccinated against covid-19, even with Delta or the next scary variant around, is one where far fewer people will be at risk of dying or getting seriously harmed than the world we’ve lived in over the past year and a half. High vaccination rates may not prevent transmission altogether, but they will still help control its spread and lead to fewer cases in the community. That control will in turn buy us time against the unlikely but possible scenario of much more evasive strains that can gravely sicken and even kill many vaccinated people, something that thankfully isn’t happening currently.
Right now, though, only 28% of the world’s population is estimated to have gotten partially vaccinated, and 14% is fully vaccinated. In the U.S., there remain far too many pockets of middling vaccination rates that will allow Delta to spread like wildfire. Just yesterday, the U.S. once again reported the most cases in the world—an ignoble distinction it had held onto through much of the pre-vaccine era. Hospitalizations and deaths aren’t expected to rise to the peaks seen earlier this year, but they are increasing again. Just as before, people have died and will continue to die unnecessarily.
Vaccinated people are understandably worried about an increased risk to themselves and vulnerable loved ones with Delta around, and that’s led to speculation about the need for booster shots. While boosters may be needed eventually, especially for people with lower protection to start with, like the elderly or immunocompromised, the greatest barrier to turning the tide against covid-19 isn’t the vaccinated—it’s the unexposed and unvaccinated. Herd immunity hasn’t been reached, especially worldwide, no matter how many op-ed columns have wished it so since last year. And even if Delta does burn through the U.S. quickly, as it seems to have done in the UK and India, that’s no guarantee that covid-19 will remain dormant from then on.
This latest spike has led to a renewed call for vaccine mandates. The U.S. seems unlikely to pursue a national mandate (and may be limited in its ability to do so), but more and more private businesses and parts of the government are moving forward with them. If they come, though, mandates are only one part of the equation to getting people vaccinated, and more will need to be done to get rates higher.
If most people are now destined to be exposed to covid-19 eventually, that doesn’t mean everything is out of our control. We can still try to mitigate its spread during this latest or future waves, including through the use of masks, and even when it’s circulating at a low level in communities through simple measures like staying home when sick or wearing a mask if you must be out while sick—a smart thing to do even if covid-19 weren’t in the picture. The more we slow its spread now, the more time there will be to vaccinate the rest of the world and populations like young children, as well as to boost the protection of high-risk groups like the immunocompromised. Covid-19 may be here to stay, but the amount of harm it has left to cause is still up to us.