COVID-19 mutant variants and herd immunity

00:00 / 00:00



Content Reviewers


By now, you’ve likely heard about the new variant strains of COVID-19 that are circulating around the world.

There are a number of concerns with these new strains, as they may make it easier to spread COVID-19 to others, and they may increase the severity of COVID-19 illness.

This video aims to explain what is known about the different strains and how they may affect achievement of herd immunity.

All viruses mutate. As more people get infected with a virus, the virus has more opportunities to multiply and there are more chances that a mutation may occur.

A mutated virus can be considered a new strain when the virus has enough mutations to make it distinct from the original virus.

So, often new strains appear in places with uncontrolled outbreaks.

The new strains can become a problem when the mutation gives the virus an advantage, such as making it easier to quickly spread or increasing the infection severity.

For each of the COVID-19 variant strains, it’s likely the mutations took place within a single patient who was infected with the virus for a long period of time.

Most relevant COVID-19 mutations affect the spike protein, which is a protein located on the outside of the virus that can bind to the host cell, helping the virus enter the cell.

The genetic code for the spike protein is within the “conserved” region, meaning the spike protein tends to be consistent across each new generation of the virus.

Most of the developing vaccines have been targeting proteins on the viruses, one of which is the spike protein, so alterations in the spike protein may make vaccines somewhat less effective.

As of early March 2021, there are three clinically important strains of COVID-19: B.1.1.7, also called the UK strain, B.1.351, also called the South African strain, and P.1, also called the Brazilian strain.

While there are a number of other strains that exist, these three strains are clinically important because they potentially may be more contagious and more virulent than the original COVID-19 strain.

B.1.1.7 was first discovered in the United Kingdom in late 2020 and contains multiple mutations, including those within the spike protein.

By December of 2020, it was reported to be present in numerous countries including the US.

This strain is considered to be one of the most transmissible, and it spreads between people 25 to 40% faster than the other COVID-19 strains.


Several different mutant variants of the COVID-19 virus (SARS-CoV-2) have been identified. Some of the known variants of the COVID-19 virus include variant B.1.351(Beta), which was first identified in South Africa in October 2020; P.1(Gamma) discovered in Japan in late 2020; and B.1.1.7 (Alpha), which was first discovered in the UK in late 2020.

The spread of new variants implies that more people will need to be vaccinated to achieve herd immunity. Herd immunity is the resistance to the spread of an infectious disease within a population, which occurs when a sufficient percentage of the population has been immunized, or vaccinated against the disease. For covid19, its currently estimated that herd immunity can be achieved if a population is vaccinated at above 66%.


Copyright © 2023 Elsevier, its licensors, and contributors. All rights are reserved, including those for text and data mining, AI training, and similar technologies.

Cookies are used by this site.

USMLE® is a joint program of the Federation of State Medical Boards (FSMB) and the National Board of Medical Examiners (NBME). COMLEX-USA® is a registered trademark of The National Board of Osteopathic Medical Examiners, Inc. NCLEX-RN® is a registered trademark of the National Council of State Boards of Nursing, Inc. Test names and other trademarks are the property of the respective trademark holders. None of the trademark holders are endorsed by nor affiliated with Osmosis or this website.