In the short time since the omicron variant was identified in South Africa in November 2021, researchers have quickly learned that it has three unique characteristics: It spreads efficiently and quickly, it generally causes milder disease than previous variants and it may confer strong protection against other variants such as delta.
This has many people wondering whether omicron could act as a vaccine of sorts, inoculating enough people to effectively bring about herd immunity and end the Covid-19 pandemic.
Two immunology researchers at the University of South Carolina who are working on inflammatory and infectious diseases, including Covid-19, “find the characteristics of omicron in the pandemic setting particularly intriguing. And it is these characteristics that can help answer that question.”
According to available data, some 4.73 billion people across the globe – about 61.6% of the world’s population – have received at least one dose of a Covid-19 vaccine.
So, how does omicron mimic a vaccine?
All vaccines work on “the principle of training the immune system to fight against an infectious agent. Each vaccine, regardless of how it is made, exposes the human or animal host to the critical molecules used by the infectious agent – in this case, the SARS-CoV-2 virus – to enter the host’s cells,” the two scientists argue.
In an article on “The Conversation,” Dr Prakash Nagarkatti and Dr Mitzi Nagarkatti add that some vaccines expose the host only to select portions of the virus.
In some respects, they say, omicron mimics these “live attenuated vaccines because it causes milder infection and trains the body to trigger a strong immune response against the delta variant,” as shown in a recent study that is not yet peer-reviewed from South Africa.
The high transmission of omicron combined with ongoing vaccination efforts could help attain herd immunity soon and end the most acute phase of the pandemic. However, there is little chance of it eradicating Covid-19, since all signs point to the likelihood that the virus will become endemic – meaning SARS-CoV-2 will be in circulation but will likely not be as disruptive to society.
So what exactly triggers strong and lasting immunity? The lifelong immunity seen in certain infections such as smallpox can be explained by a phenomenon called “immunological memory.”
“After the B cells and killer T cells first encounter the virus, some of them get converted into what are called memory cells, which are known to live for several decades.”
For this reason, memory cells are critical for establishing strong, long-lasting immunity. This is evidenced from studies with smallpox in which people that were infected or vaccinated were found to have the antibody response even after 88 years! Why some infections or vaccines trigger long-lasting memory and others do not is under active investigation. Because Covid-19 is only two years old, researchers don’t know yet how long the memory B and T cells last. All of these considerations leave room for hope that when new variants of SARS-CoV-2 inevitably arise, omicron will have left the population better equipped to fight them. So, the Covid-19 vaccines combined with the omicron variant could feasibly move the world to a new stage in the pandemic – one where the virus doesn’t dominate our lives and where hospitalization and death are far less common.
The scientists warn, however, that omicron should not be considered a viable alternative to the existing vaccines.
For one, Covid-19 infection can result in severe illness, hospitalization or death, especially in vulnerable individuals with underlying conditions. It can also cause long-term health effects in some people, called “long Covid.”
Editors, MDT/The Conversation
