We are committed to keeping our readers informed.
We removed our paid access to essential coronavirus news. Become a subscriber to support our journalists. subscribe now.
Since the new coronavirus first appeared in Wuhan, China in late 2019, it has mutated thousands of times, resulting in numerous variants. While this may sound alarming, it is not so remarkable: all viruses mutate and, compared to other common viruses, the rate at which the coronavirus goes through this natural process is very slow. But in the past few months, a number of notable variants have emerged, prompting researchers to raise the alarm for one reason or another: a British variant, a South African variant, a Brazilian variant and a variant found in California.
Although each of the aforementioned variants carries its own set of risks – both the British and the South African variants appear to have significantly higher transmission rates, current research shows, while the Brazilian variant has caused an outbreak of cases in which the virus already infected a large number last spring – of extreme concern is whether the available COVID-19 vaccines are effective against mutations. To better understand the variants and exactly how we should be concerned, Cut spoke to Michael Worobey, a professor of evolutionary biology at the University of Arizona who studies the evolution of influenza viruses.
This interview was slightly condensed and edited.
The main variants that we hear about now are the British variant, the South African variant, the Brazilian variant and the variant found in California. Are there others that should be on our radar?
Those are the big ones now.
And what do we know about each of its transmission rates and death rates?
The British variant appears to be considerably more transmissible – up to 50 percent higher – and there is evidence that it generates a greater amount of virus in the nose and throat of infected people, which is probably the reason for its rate of transmission. There is also very convincing evidence that it also causes a higher death rate. My undergraduate students and I posted a scientific article [that has yet to be peer-reviewed] showing that the British variant probably settled in November in California and Florida. So, he had a head start.
The South African variant also appears to be more transmissible – as much as the British variant, if not more. I’m not sure where things are in terms of the death rate, but it wouldn’t be surprising if it were similar to the British variant. At the moment, we don’t have good information about the Brazilian or Californian variant yet. However, with the Brazilian variant, judging by the mutations it has, which are some of the same ones that we think are causing the increase in transmissibility in the British and in South Africa, I would not be surprised if it were more transmissible.
Obviously, you don’t want any of these rates to be high, but is one more worrying than the other?
Let’s start with the death rate. Imagine that the virus infects 100 people. How many of them are going to die? Now, just to get into the bush a little bit, the mortality rate is not a fixed constant. For example, if you are in a European population where there are some people at the older end of the spectrum, the death rate will be higher than in countries where there are not that many elderly people, because the virus is much milder in younger people. The transmission rate determines how many people get the infection.
Even without a higher mortality rate, with a higher transmission rate, more people will die than they would have died had this variant not appeared. And this is dramatic. In England, hospitals are full of patients who would not be there if the variant were not so transmissible, and that is reserved for us here in the United States. The variant has its hooks inside us. In three, four months, almost all, if not all cases of the virus, will be caused by variants.
Last week, Moderna announced that its vaccine was effective in protecting against British and South African variants, although its effectiveness rate has dropped to the latter. Still, the company said that neutralizing antibodies were generated by the vaccine. But now, Moderna and Pfizer are developing booster doses to add to their vaccine regimens, specifically to protect against variants. How do we process this information? Are approved COVID-19 vaccines effective against variants or will they slowly become obsolete?
I think companies are just being cautious and starting this work if it is beneficial, but at the same time, studies that are happening simultaneously are indicating that, fortunately, this may not even be necessary. At the moment, there is no indication that vaccines will fail against these new variants. In fact, the vaccine appears to produce a more powerful immune response than natural infection.
If we already know that available vaccines are 95 percent effective, in the best case scenario, some people will be infected after vaccination. Now, I really think that if you take the vaccine that was generated with the original formulation and use it in an area with a variant with an escape mutation, it will be a little less effective. But it is difficult to quantify how much less effective. [Editor’s note: This interview was conducted before Johnson & Johnson unveiled a summary of the results for its global vaccine trial, effectively corroborating Worobey’s assessment: In the U.S., the vaccine was 72 percent effective against moderate to severe cases; in South Africa, where most COVID-19 infections are caused by that country’s variant, the efficacy rate dropped to 57 percent.]
There have been some reports about the Brazilian variant possibly causing reinfection. Could you be avoiding antibodies made against the previous version of the virus?
The Brazilian variant has a specific mutation called E484K, and we know from laboratory experiments that this mutation may allow the virus to escape some antibody responses. For some people, this can make a difference and allow them to be reinfected, but the good news is that, as far as we can tell, vaccines have sufficient protection in terms of how powerful the antibody response they generate is. For most people, this mutation is unlikely to allow the virus to escape that response completely.
I would also like to mention the reports that the British variant may have originated in an immunocompromised patient. Could you clarify that connection for me?
Yes, this is what most people think happened. The British variant has so many mutations that it does not fit what we call the molecular clock of viruses, where we expect a mutation of this virus every two weeks. This virus has caught so many mutations that it looks like it has come back from the future.
The variant has some amino acids that are deleted in the spike protein, and these same mutations – the deletion at sites 69 and 70 of the spike protein – have appeared several times in immunocompromised and chronically infected people with the virus. People’s immune systems are not functioning properly; they can’t eliminate the infection like most people, so they end up being infected for months. And in several cases, these people have been treated with what is called convalescent plasma, which is basically just antibodies from someone who has been infected.
This should certainly inform how we treat immunocompromised people, who can be a crucible to generate the next variant of concern. We really need to be very careful about the progressive transmission of chronically infected patients. If they are in the hospital, that means keeping them isolated and applying very strict procedures to limit interaction with staff or visitors.
Do you think we will see other variants appear that are so alarming?
These will not be the last variants we hear about. Once we vaccinate everyone, the virus will experience a much stronger selective force to create new variants that escape immunity to some degree. Where there is a major launch of vaccines in the coming months, we will see the mutation process accelerate. Now, how concerned should we be? Once again, we must be quite sure that, for most people, the vaccine will still last. But again, the virus will also continue to evolve. I think we will need to update vaccines at some point in the future, although it is difficult to say exactly when.
So, what exactly do we do with this information? How should you inform our actions in the foreseeable future?
For me, it’s another reason to keep the face mask on and hope that the people around you do it too. This has become much more important. If we didn’t have the potential vaccine cavalry on the horizon, we would have a lot of problems in this country in March and April. Therefore, we hope that the logistical issues and errors that characterized much of our country’s response to the virus can be resolved.