COVID-19 cases are up, the delta variant is plowing through the unvaccinated population, and people are dying. It’s scary times, but how scary is it for those who are vaccinated?
Some general background
Let’s talk a bit about variants and vaccines more generally before we dive into the delta variant and the COVID vaccines.
What is a variant?
First off, what’s a variant? Viruses mutate; it’s what they do. Their goal (to anthropomorphize something that isn’t technically alive) is to reproduce their genome, which they do using the host’s cellular machinery. Some viruses mutate faster, while others do it slower; the amount of the genome that changes with each mutation also varies. The influenza virus mutates a lot, and that’s part of why you need a new flu shot every year.
If the genome has shifted significantly enough and it starts to change how the virus is behaving, it’s given a name and we hear it talked about as a variant. Variants branch off from the original viral genome, and then new variants can develop and branch off from there. There are many more minor variants with minor mutations, but the ones we hear about are the more significant ones.
How vaccines protect you
Vaccines don’t create a magic forcefield around your body that keeps the virus out. They trigger your body to make antibodies that recognize a certain target on the virus (or bacterium). If you’re vaccinated and someone germy sneezes on you, your nonexistent forcefield doesn’t repel the virus. Those viral particles swim into your respiratory passages just like they would if you weren’t immunized.
If you are immunized, though, your immune system says aha, I recognize this! It starts pumping out antibodies that latch onto the virus so that other parts of the immune system can quickly knock it down. It doesn’t cause an infection, and if you were tested for the virus, that test would come back negative.
A “breakthrough infection” occurs when your immune system recognizes the virus, but the virus gets its foot in the door before your immune system can get it under the control. It is not an indicator that the vaccine no longer works. The likelihood of this can depend on the infectious agent and whether you’ve received your full sequence of vaccinations. However, your body is still much better equipped to handle the virus than if you hadn’t been vaccinated at all, so you would likely only get a relatively mild infection before your immune system shuts it down.
Breakthrough infections can simply be a “confirmed infection,” which means the virus got its foot in the door enough that it shows up on a lab test (but the individual isn’t necessarily asymptomatic), or they can be a “symptomatic infection,” which means the virus got its foot in far enough to cause symptoms.
The delta variant
The non-technical naming system used for the COVID-19 virus has been based on the Greek alphabet (alpha, beta, gamma, delta, and next up epsilon…). It’s kind of like how Atlantic hurricanes are named starting with subsequent letters of the alphabet. There are also more specific technical names to the variants, but for our purposes, those aren’t particularly relevant.
Scientists have already identified the genome of the delta variant. Public health agencies are regularly sequencing samples from labs so that they know exactly what’s circulating through the population. In the US, the CDC (Centers for Disease Control and Prevention) has paired with large national labs and seven universities to scale up this process. There are other groups doing additional sequencing work. While it may look like a big unknown to us, the people that need to know waaaaaaay more than we do. All those COVID tests that labs are doing aren’t just getting chucked in the garbage after they come back positive; those samples and that information is getting used, and one of those uses is sequencing.
The delta variant contains mutations at several points in the viral genome, including three mutations in the part of the genome related to the spike protein, which is used to enter human cells. The delta variant appears to be more transmissible than the wild-type COVID-19 (aka the original strain), meaning it passes more easily from person to person. It also appears to be more likely to make people sicker if they do get infected.
Currently, the delta variant is the predominant strain seen in the US. Deaths are spiking after having trended downward, but 99% of those deaths, as well as 97% of hospital admissions, are in unvaccinated people.
Do the current COVID vaccines still work? As per the CDC, “available evidence suggests the currently authorized mRNA COVID-19 vaccines (Pfizer-BioNTech and Moderna) are highly effective against hospitalization and death for a variety of strains,” including the delta variant.
Studies are still being done to evaluate the effectiveness of the other vaccines for the newer variants, and further studies are also needed to evaluate the effectiveness of the mRNA vaccines in people who are immunocompromised. Note: I’ve stuck with information from the US CDC for this post, and the US isn’t using the AstraZeneca vaccine.
The vaccines aren’t quite as effective at preventing breakthrough infections with the beta, gamma, and delta variants as they are with the wild-type (original) strain or the alpha variant. However, when vaccinated people do get breakthrough infections, they don’t get nearly as sick, and they also appear to be less likely to transmit the virus to others as compared to unvaccinated people who become infected.
Recognizing the neighbourhood
The CDC says that “Both vaccination against and natural infection with SARS-CoV-2 produce a ‘polyclonal’ response that targets several parts of the spike protein. The virus would likely need to accumulate multiple mutations in the spike protein to evade immunity induced by vaccines or by natural infection.”
Essentially, that means the virus would need to mutate a lot for your antibodies not to be able to recognize some part of it, and current evidence doesn’t point to that having happened. As a loose analogy, let’s consider the neighbourhood where you live and that you know well. A few houses could get renos and look a little different, but you’re still going to recognize the neighbourhood. Quite a few houses would have to be torn down and rebuilt before you can no longer recognize that it’s your neighbourhood. Your immune system knows that particular viral neighbourhood because the vaccine has given it the close-up tour, and renos on a few houses don’t stop the immune system from being able to recognize the neighbourhood.
Public health agencies worldwide are monitoring vaccines’ effectiveness against the delta variant, and they’re keeping a very close eye on any hospitalizations or deaths that may occur. Some breakthrough infections are expected even if the effectiveness of the vaccines is maintained. “Escape mutants” is the term used when the virus changes enough that’s able to go undetected by vaccine-induced immunity (returning to the neighbourhood analogy, it’s changed enough such that your immune system can’t recognize it any longer). The CDC says “There is no evidence that this is occurring, and most experts believe escape mutants are unlikely to emerge because of the nature of the virus.”
At this point, the single most important thing to do to protect yourself and those around you is to get fully vaccinated. If that changes in the future, that will have to be dealt with as it comes up, and the role of public health agencies is to identify that as quickly as they can, but getting vaccinated is still the most effective thing you can do right now.
With vaccines in general, a single dose of a vaccine doesn’t typically generate enough of an immune response to give long-term protection. When you get the first dose, the body tends to produce mostly a type of antibodies known as IgM. IgM antibodies don’t stick around that long.
With subsequent doses, the body produces more IgG-type antibodies, which do stick around for a longer period of time. Therefore, subsequent doses give more lasting protection in a way that may not be able to happen with the immune system’s initial exposure to an antigen.
There are a lot of routine vaccines that require boosters. It remains to be seen what that will look like with regards to COVID in the longer term.
Herd immunity refers to the extra protection that comes from a certain threshold percentage of the population being immune. Let’s say your herd consists of sheep in a pasture. If you can get enough sheep immune, let’s say by vaccinating enough, then it’s hard for an infectious agent to jump around in your pasture because there are so few bodies that it can jump to. The vaccinated part of the herd then ends up protecting the sickly little lambs and the sheep who weren’t able to get vaccinated. Enough of the herd is protected that the infectious agent just can’t get to the vulnerable ones.
The more contagious an infectious agent is, the higher the threshold that’s required to reach herd immunity. Measles is highly contagious, and that fast and easy spread of infection means that the threshold to achieve herd immunity is also high, at 93-95% (as per the WHO).
Will herd immunity be possible with COVID? Quite possibly not. For even the slightest possibility of achieving herd immunity through everyone having been naturally exposed to COVID, a whole lot of people would have to die. For whom would that be an acceptable price to pay?
From the science to the public measures
The information that’s being passed to the public is coming through a filter. It’s not that information is being hidden; there’s a lot of information that’s available on sites geared towards health professionals and scientists, and there’s a huge amount of data-sharing going on in the scientific/public health community. However, without the relevant scientific background, the average person isn’t prepared to understand the data itself or what it means, so data dumping on them isn’t useful.
If you’re curious, though, here’s an article published August 12 in the New England Journal of Medicine that’s not overly technical relative to papers that get really detailed on the structure of the virus: Effectiveness of Covid-19 Vaccines against the B.1.617.2 (Delta) Variant.
Recommendations to the public keep changing because that’s very much the blunt end of the stick. The scientists present the objective facts as they become known, but choices about what to do with those facts are far more ambiguous and subjective. What makes the most sense scientifically isn’t necessarily going to be the most acceptable socially, and someone has to make decisions about priorities.
For example, a paper published in Emerging Infectious Diseases by Swadi et al. in January 2021 showed that pre-flight screening was not enough to stop COVID transmission on airplanes, and the authors suggested there could be a benefit from pre-flight quarantine. Public health officials have to make decisions about whether the pros outweigh the cons of making these kinds of interventions. That’s not always easy, and politicians don’t always want to go along with public health recommendations anyway.
Public health officials have been urging people to get vaccinated, but that doesn’t mean that people listen. Vaccine hesitancy (and adamancy against) is still very much a thing. In a press conference on July 16, 2021, CDC director Rochelle Walensky said “This is becoming a pandemic of the unvaccinated.”
There are countries where limited amounts of vaccine are available, while in wealthy Western countries, there are plenty of doses available, and some governments are offering financial incentives to try to motivate people to get vaccinated.
Sounds like the voluntarily unvaccinated need to step up to the plate.
- CBC News (July 16, 2021): ‘Pandemic of the unvaccinated’: COVID-19 deaths up 26% over previous week in U.S.
- Centers for Disease Control and Prevention (CDC): COVID-19 Science Update released: January 15, 2021 Edition 72
- CDC (Aug 6, 2021): Delta Variant: What We Know About the Science
- CDC Science Brief Jan. 28, 2021): Emerging SARS-CoV-2 Variants
- CDC Science Brief (July 27, 2021): COVID-19 Vaccines and Vaccination
- Johns Hopkins Medicine (July 23, 2021): New Variants of Coronavirus: What You Should Know