Wednesday, Aug 17, 2022

Covid-19: 'Super Immunity' Might Save India From Omicron But Here's The Catch

Amid a global discussion to try booster shots of Covid-19 vaccinations which also found an echo back home in India, a section of scientists seem to now be looking at the way Omicron will react to previously acquired immunity from natural infection and vaccination.

Omicron in India PTI/File Photo

Radioactive spider bites may not lead to superpowers in real life but can a Covid-19 infection followed by vaccination result in 'super immunity?' That's what a recently published study seems to be claiming. With the emergence of Omicron, the latest variant of Covid-19 supposedly three times most transmissible than the fatal Delta variant, healthcare experts, researchers and epidemiologists across the world have been scratching their heads trying to figure out the properties of the new variant. And the variant has done its best to puzzle observers.

While studies suggest a higher rate of transmission and reinfection, the Omicron's effect has been deemed less severe than variants like Delta when it came to hospitalisation and death so far. Amid a global discussion to try booster shots of Covid-19 vaccinations which also found an echo back home in India, a section of scientists seem to now be looking at the way Omicron will react to previously acquired immunity from natural infection and vaccination.

Enter 'Super Immunity, a concept that has been under scrutiny for some time but has gained ground in recent days since the emergence of Omicron.

What is 'Super Immunity?

'Super Immunity' refers to a combination of immunity gained through natural infection and immunity gained through immunisation in a person that has faced a breakthrough infection after vaccination. Meaning, a person infected with the Sars-CoV-2 virus after being vaccinated against it gains "super immunity". According to the paper, this "super immunity" might come handy in fighting Omicron. The paper has since been widely quoted and shared on legacy and social media.

While "super immunity" might be the buzzword now, experts have been studying the phenomenon by its other name - "hybrid immunity" for some time now, especially after cases of reinfection with Delta after the two doses of Covid-19 vaccinations started stacking up.

Does "Super Immunity" work against new Covid variants?

How well a person is protected from reinfection (not disease) is based on the amount and neutralization potency of antibodies that circulate in the blood, explains virologist Shahid Jameel.

These antibodies come largely from circulating antibody-producing B cells, also called plasmablasts. Jameel, however, warns that these antibodies are short-lived and die off with time.

"That is why antibody levels fall with time. However, there are long-lived memory B cells that continue to mature and diversify to produce antibodies of higher affinity (potency) and breadth (covering variant strains). This process is enhanced by infection followed by vaccination," the former head of the advisory group to the Indian SARS-CoV-2 Genomics Consortia (INSACOG) tells Outlook.

Does natural infection offer higher immunity than vaccination? Jameel says that infection gives a much better T cell response than vaccination. However, questions remain regarding its efficacy against the latest Covid-19 since most studies on hybrid immunity were conducted pre-Omicron.

Waning immunity

One such key question is regarding the longevity of "super immunity". How long does it last? For instance, studies suggest that antibodies that are hyper-charged after natural infection tend to wane with time. "New research shows that even hybrid immunity wanes and allows more reinfection with Omicron compared to earlier variants," Jameed concedes. However, scientists belives that hybrid immunity may still hold up better than just people who got two vaccine doses. "A booster dose of vaccine further enhances this process."

Virologist T Jacob John in a previous interview with Outlook had said that hybrid immunity might be the key to preventing an Omicron outbreak in India.

"I feel hybrid immunity will see India through with relatively less harm. Many in India are previously infected with either Alpha or Delta variant and now a large proportion has also been vaccinated with at least one dose," John says.

According to NTGAI chief Dr Jayprakash Muliyil, however, the virtue was in waiting. "I agree with the theoretic logic of hybrid immunity. Unfortunately, not a shred of real evidence to suggest that 'super immunity' works against Omicron has so far surfaced," Muliyil tells Outlook.

However, the epidemiologist who is also part of the working group of the National Technical Advisory Group on Immunisation (NTAGI) which is advising India on its vaccination policy, seems to be putting its weight behind natural and vaccine immunity. The NTAGI has not made any recommendations to the centre on booster doses yet, raising calls from many to prioritise booster doses along with first and second dose of vaccinations, especially for those with vulnerabilities such as senior citizens or people with comorbidities.

In any case, "super" or hybrid immunity can only work if people are first vaccinated and then catch a breakthrough infection. While over 3.4 million Indians have been infected with Covid-19, T Jacob Joh warns that "naturally gained immunity has the risk of severe disease and death.  Hence the urgency for vaccine-induced high immunity". And In India, only 39.9 per cent of the population has so far received two doses of the vaccine.