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Rough guide to virus variants and mutants


There is a lot of confusion and fear over reports of coronavirus variants/ mutants recently. Here is a simple breakdown of what we know and don't know about these variants.

Basic terminology:

- Mutation: a particular change in the genetic code of the virus, which may/ may not make a change in the proteins the virus produces. For example, 'N501Y' or 'E484K' (which are prominently reported in the media) denote mutations in the viral genome that lead to changes at particular spots in the viral 'spike' protein.

-Variant: a virus that has accumulated a collection of characteristic mutations. For example, B.1.1.7 ('UK variant') or B.1.351 ('South Africa variant') carry characteristic mutations that differentiate them from other SARS-CoV-2 variants.

-Mutant: this is not a helpful term. 'Variant' conveys the same meaning and this is what I will use for the remainder of this post.

A COVID-19 patient rests on a bed at a makeshift hospital in New Delhi, India, Friday, April 30, 2021. AP Photo

A few points on mutations and variants:

1. It is completely normal for viruses to mutate. This is particularly true for 'RNA viruses' like SARS-CoV-2 (which is the virus causing COVID-19). The longer the virus circulates in human populations, the more it changes compared to the original version of the virus.

2. Many mutations make absolutely no difference to the virus or the disease it produces. These are called neutral mutations. Therefore, the word 'mutations' or 'mutants' doesn't automatically mean bad news. We don't really need to worry about these neutral mutations.

3. Certain mutations, however, give a variant some kind of advantage. They might make the virus more transmissible, render it easier to infect our cells, or even enable it to partially evade host immunity. This works like Darwinian evolution and such variants rapidly replace pre-existing forms of the virus. Such mutations may/ may not cause more severe disease. Viruses are simply 'trying' to replicate more efficiently. Killing people is really not their primary objective.

So, to summarise, we only care about variants that

a) transmit more easily between people, or

b) cause more severe disease, or

c) partially evade immunity from past infection or vaccination, or

d) are more resistant to treatment, or

e) escape detection by PCR diagnostics.

Variants that have one or more of these five attributes are called variants-of-concern (VOC).

So far, there are three widely-accepted VOCs: B.1.1.7, B.1.351, and P.1. The US CDC also recognizes Californian variants B.1.427 and B.1.429 as VOCs, but these are not of major concern outside the US currently.

So, what do we know about the main VOCs?

1. B.1.1.7: this is called the 'UK variant' in the popular press. This is a highly successful variant because it is considerably more transmissible than predecessor forms. The jury is still out on whether it causes more severe disease. The good news is that first-generation COVID-19 vaccines have superb efficacy against B.1.1.7. This was proven in Israel (B.1.1.7 predominant area) where an efficient vaccination campaign drove down COVID-19 cases and deaths (Dagan N et al, NEJM, 2021).

2. B.1.351: this is also known as the 'South African variant'. The recent cases of variants found in the Hong Kong community are due to B.1.351. Apart from being very transmissible, this variant carries a troublesome mutation called E484K that enables it to partially evade vaccine-induced immunity. This was shown to affect the AstraZeneca vaccine (Madhi S et al, NEJM, 2021), but Pfizer/BioNTech have reported promising preliminary results in their South African vaccine trial. It is very important to understand that vaccine-induced responses are polyclonal & involve T-cell immunity. Vaccination is still very likely to protect against severe disease due to variants.

3. P.1: this is commonly called the 'Brazilian variant'. Like B.1.351, P.1 carries the troublesome E484K mutation. However, there is good news. In Manaus (Brazil), CoronaVac (Sinovac) still maintained rates of protection against symptomatic COVID-19 that were comparable to its Phase III trial (Hitchings M et al, medRxiv, 2021). There is also data from Brazil that vaccination campaigns (with CoronaVac and AstraZeneca) reduced mortality in elderly people considerably even though P.1 was predominating in the country (Victora CG et al, medRxiv, 2021). This supports the prediction that vaccines are also going to be decently protective against severe B.1.351 variant infection.


What about B.1.617 - the so-called 'double mutant' from India? Firstly, 'double mutant' is a nonsensical name because all variants carry several mutations (not just two). Furthermore, preliminary evidence suggests that B.1.617 doesn't really evade vaccine induced immunity that much (Yadav P et al, Biorxiv, 2021). So, it is less of a concern in this respect than B.1.351. The effect of B.1.617 on virus transmission or disease severity is basically not known at this time. As I have noted in a previous post, there are plenty of human behavioural factors driving the current situation in India without having to blame it on a 'double mutant'.

The message is simple:

1) Get vaccinated! Vaccination is your best defence against COVID-19, whether or not due to a variant.

2) Variants are not an excuse for discrimination against any community/ ethnic group.

3) Stay calm and compassionate. The end is in sight.

Have a good week ahead.

This article is first published on the author’s Facebook.


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