Will Omicron Variant Aid or Stall Herd Immunity? Experts Say Nature of Variant, Vaccine Efficacy Key

Can the newly emerged Omicron variant help or decrease the chances of achieving herd immunity against the Covid-19 pandemic? Experts hold different views, depending on a variety of factors that have most to do with the nature of this variant — complete information on which is awaited and will likely take a couple of weeks to solidify.

But what is herd immunity and why has it been a hot topic since the pandemic began? Herd immunity, also known as community immunity, occurs when a large portion of a population in a given area is immune to a specific disease. If enough people are resistant to a disease’s cause, such as a virus or bacteria, the disease has nowhere to go.

While not every individual is immune, the group as a whole is protected. This is due to the fact that there are fewer high-risk individuals overall. Infection rates fall, and the disease dies out. Herd immunity safeguards vulnerable populations. Babies and those with weakened immune systems who are unable to develop resistance on their own are among those at risk.

And how is herd immunity achieved? It can happen in one of two ways. Natural resistance can be developed. When you are exposed to a virus or bacteria, your body produces antibodies to fight the infection. When you heal, your body retains these antibodies. Your body will fight off another infection. This is what brought the Zika virus outbreak in Brazil to a halt. Within two years of the outbreak’s start, 63 percent of the population had been exposed to the virus. According to researchers, the community has reached the optimal level for herd immunity.

Vaccines can also cause resistance to develop. They trick your body into believing it has been infected by a virus or bacteria. Even if you do not become ill, your immune system continues to produce protective antibodies. The next time your body comes into contact with that bacteria or virus, it will be prepared to fight it off. This is how polio was eradicated in the United States.

Omicron Alters Vaccine Response

Ever since the Omicron variant was recognised, major vaccine companies such as Moderna and Pfizer have said they will assess data to establish the efficacy of their jabs against the new variant, deemed to be even more infectious than the Delta variant.

In India, scientists at the Indian Council of Medical Research-National Institute of Virology (ICMR-NIV) in Pune have begun efforts to isolate and grow the Omicron strain of the novel coronavirus from the Dombivali man’s throat/nasal swab sample. The scientific experiment will answer two critical questions: Will this variant affect the efficacy of Covishield and Covaxin, and will it outfight existing antibodies in people who have had Covid illness from older strains?

According to reports, the mutations in the new variant suggest that it is likely to evade vaccine protection to some extent, but that it is unlikely to cause more severe illness than previous versions of the coronavirus.

These findings appear to be consistent with real-world observations from places such as South Africa, where infections have included the vaccinated and previously ill, but have been largely mild thus far. That data, however, has been extremely limited thus far, and much of the current evidence has come from computer modelling and comparing omicron’s physical structure to previous variants, reports state. Omicron also appears to be susceptible to the body’s second line of defence, T-cells. They collaborate with antibodies to prevent infection and disease development. If a virus manages to evade antibody attacks, T-cells go to work killing infected cells.

Charles Chiu, a microbiologist at University of California told the Bloomberg in a report that he was in the camp of scientists that suspected the delta variant was “the beginning of the end of the pandemic” but that he was “surprised by Omicron”.

Even if omicron does not cause more severe infections in most people, an increase in cases would result in more hospitalizations and deaths due to the sheer number of infections, he said. And as long as there are a large number of unvaccinated people on the planet, the virus will continue to spread and mutate.

Omicron also demonstrates that SARS-CoV-2 is highly adaptable and may be difficult to completely eradicate, he said. According to Chiu, public-health policy should shift away from attempting to eliminate the virus from circulation through vaccination and instead focus on preventing severe disease.

Omicron Changing Numbers Needed for Herd Immunity: Expert

A leading virologist who has raised awareness about the coronavirus disease said in a report that the percentage required to achieve herd immunity is changing rapidly due to the emergence of new variants such as omicron. “The percentage required to achieve herd immunity is changing as a result of new and highly transmissible variants like omicron,” Akiko Iwasaki, Professor of Immunobiology at Yale University, said on Tuesday at the Hindustan Times Leadership Summit (HTLS). “The needle keeps moving up, we need to immunise more and more people,” the professor said, adding that the herd immunity percentage for omicron was not yet known.

The expert called for increase in mask-wearing, mandatory vaccinations and Covid curbs to stop the spread. “We now know that masks help in stopping the spread of infection. It was not encouraged in the initial stage. In fact, implementation of measures like these was less than desirable in early days. Then there are hesitancies around different vaccines. Mandatory vaccinations very important to contain the virus,” she said.

Some Experts Say Herd Immunity May Suffer, But Some Hold a Ray of Hope

Dr. Uday Narlawar, head of the department of community medicine at Government Medical College and Hospital (GMCH) in Nagpur, and told the Times of India that if the existing antibody in the local population fails to match the antigens in the Omicron variant, herd immunity will suffer.

“According to national reports and other local findings, the Nagpur population is likely to have developed herd immunity,” Dr Narlawar said. “However, it may no longer work as a protection if the Omicron mutations change the antigenic structure to such an extent that it starts behaving as a completely new virus.”

“A large section would become susceptible if antibodies grown in the 70-80 percent of the population with sub-clinical infections during Covid-19 (asymptomatic) fail to match the significantly changed antigenic structure of the new variant Omicron,” he said.

Meanwhile, Dr. Mohan Joshi, senior assistant professor, department of community medicine, NKP Salve Institute of Medical Sciences and Research told the Times of India that infection-induced immunity from previous variants of the coronavirus such as Alpha, Delta, and Delta plus will help us in the long run to meet Omicron.

He said previous serosurveillance studies have shown that even without immunisation, 90 percent of the 0-18 population has antibodies. “Because the adult population is already immunised to a large extent, this plays a critical role in herd immunity,” he explained.

“Indians may also have ‘non-specific immunity,’ which may have protected them from the coronavirus.” This ‘non-specific immunity’ has grown as a result of the presence of various other viruses in the country, which has, to some extent, trained our immune system to fight virus types and variants,” explained Dr Joshi.

Dr. Ashok Jadhao, head of the department of community medicine at Indira Gandhi Medical College and Hospital, said in the TOI report that if the Omicron variant is truly mild, as early reports suggest, it may aid in boosting herd immunity. He said the role of the herd community had been called into question because many people who had received both vaccine doses and had previously tested positive for Covid.

Nonetheless, the severity of the disease was unquestionably lower in them. “Logically, based on the number of active cases hovering around 50, we may have reached a certain level of herd immunity or fruitful fallout from the immunisation drive undertaken thus far. Perhaps for these reasons, we can say the disease is now in the endemic stage in Nagpur,” said Dr Jadhao.

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