Covid-19 vaccines produce T cell immunity that lasts and works against viral variants

Over the past year or so, ordinary people have learned a lot about viruses, vaccines, and the immune system. We have all had to digest a lot of complex specialist knowledge about the safety and effectiveness of Covid-19 vaccines.

But one important – and positive – aspect of vaccines has not been well communicated. Statistics on the effectiveness of the Covid-19 vaccine have only focused on one aspect of immunity: antibodies.

But there is also another aspect: T cells, a key part of our immune system. And the good news is that current vaccines stimulate your T cells to fight both the SARS-CoV-2 virus and its emerging long-term variants.

Let’s recap how the immune system works.

The immune system protects us from various infectious diseases, caused by bacteria, viruses, fungi or parasites. To do this, he first determines what type of infectious agent, or pathogen, is causing the infection.

Then he puts up an appropriate response. Importantly, at the same time, it produces memory cells capable of recognizing the same pathogen in the future. This allows the immune system to fight off potential re-infections.

If the immune system determines that an antiviral response is needed, it initiates a combination of two types of immunity.

One is antibody mediated and the other is T cell mediated, or cell mediated. Antibodies bind to viruses and neutralize them, preventing them from infecting cells. During this time, the T cells kill cells that have already been infected with the virus.

While both types of immunity are important in fighting viruses, cell-mediated immunity is much more effective in eradicating viruses and more sustainable. This is important in the continued fight against Covid-19.

A powerful weapon

Research has already established that cell-mediated immunity is a powerful weapon against human coronaviruses, family including SARS-CoV-2.

A 2016 study showed that T-cell immunity to SARS coronavirus persisted for up to 11 years. It offered comprehensive, effective and long-lasting protection against SARS.

Our own recent research argues that more attention should be paid to the development of vaccines capable of producing antibodies, but which primarily elicit a cell-mediated immune response against SARS-CoV-2 and its variants.

And, although most people don’t know it, existing Covid-19 vaccines offer a resilient cell-mediated immune response.

It’s not just antibodies

The immune system is generally quite good at eradicating most pathogens. But not everyone’s immune system is as good at dealing with the same pathogen; sometimes he needs a little help. Vaccines train the immune system to recognize and respond to a particular pathogen, without first having to be infected with it.

Traditionally, most vaccines contain only a small part of the pathogen. This prepares the immune system by mimicking natural infection.

Current Covid-19 vaccines used in South Africa contain small portions of wild type SARS-CoV-2 spike protein – this coronavirus was responsible for the initial Covid-19 epidemic and spread during the early stages of the pandemic.

But, as the pandemic progressed, the virus mutated. Mutations in the spike protein confer some selective advantages to the virus. Some of these mutations made the virus easier to transmit or helped it escape the immune system. The emergence of variants has raised concerns about the effectiveness of existing Covid-19 vaccines.

During the pandemic, the news and Press Releases informed about the efficacy and efficacy of various Covid-19 vaccines against emerging variants. But the reports have focused almost exclusively on the ability of the vaccine-induced antibodies and their effectiveness in neutralizing the variants.

A resilient cell-mediated immune response

This emphasis on antibodies means that any new decrease in the effectiveness of antibodies against emerging variants is cited as evidence that vaccines may not work well in the long term.

This may foster a lack of public confidence in the science behind the design of Covid-19 vaccines. And this lack of confidence could contribute to vaccine hesitancy. After all, some might say, why take a vaccine that seems less effective against each emerging variant?

In reality, many recent papers demonstrated that while the SARS-CoV-2 variants could escape neutralizing antibodies, the cell-mediated immune response induced by most of the Covid-19 vaccines currently in use is very resistant and remains effective.

While the antibodies induced by the vaccine were able to bind to the variants, they were less able to neutralize them.

T cells, on the other hand, were largely as sensitive to variants as they were to wild-type virus. They were still able to recognize and respond effectively to variants, conferring resistant protection against disease.

To date, only Johnson & Johnson has published a media statement which includes statistics on the two types of immune responses induced by its vaccine.

Research shows that the levels of antibodies produced by different vaccines decrease over time and, although immunity varies from person to person, immunity against Pfizer and the Johnson & johnson vaccines usually last at least six months.

Building public trust

Reluctance to vaccinate is a major obstacle in the fight against the pandemic. A recent investigation showed that only 72% of South Africans were ready to be vaccinated against Covid-19.

The idea that “the vaccine will be ineffective” was one of the most common reasons people gave for hesitating to vaccinate. The hesitation is not surprising if people only hear about how part of the immune response becomes less effective against emerging variants.

Public confidence in the vaccine hinges on understanding the overall effectiveness of the vaccine-induced immune response and reporting statistics on both types of response to variants.

Existing Covid-19 vaccines offer a resilient cell-mediated immune response. Knowing this can help people make an informed decision about vaccination.

Dewald Schoeman, PhD student, Molecular Biology and Virology, University of the Western Cape and Burtram C. Fielding, Professor and Director: Research development, University of the Western Cape

This article is republished from The conversation under a Creative Commons license. Read it original article.