Far from over. ‘Trained immunity’ ensures better Covid-19 virus clearance, says molecular immunologist  

Humans by nature have no ‘future immunity’ against pathogens and the future of Covid-19 depends on how the virus evolves especially in terms of immune-escape and disease-causing abilities as well as the type of immunity acquired either through natural infection or upgraded vaccination, says Dr Satish Ranjan, a Germany-based molecular immunologist. 

The Covid-19-causing coronavirus is still undergoing ‘favourable mutation’ with immune escape and disease-causing abilities which requires a country like India to increase genomic surveillance of emerging variants and closely monitor the disease severity, according to Dr Ranjan, who is also Group Leader (Jr) at the Institute of Advanced Materials, Sweden. 

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‘Trained immunity’ helps

The Omicron BF.7 variant has immune-escape abilities and a high infectivity rate, but an already ‘trained or acquired immunity’ from previous variants elicits a better and more robust response ensuring improved virus clearance and reduced disease severity. It is highly unlikely India will face a situation that China, for instance, finds itself faced with, Dr Ranjan wrote to businessline. 

“But we must be aware that the pandemic is far from over thanks to the ability of these variants to infect and cause disease in individuals. The world will continue to face a challenge till the virus undergoes ‘unfavourable mutation’ that makes it impossible for it to escape immunity gained through natural infection or vaccination and cause severe disease,” he added.   

Sequence more samples

Only a new variant completely different from existing ones, and capable of entirely escaping immunity causing severe diseases can alter the current situation. Samples from immune-compromised patients, chronic patients with immune disorders and those with compromised immunity must be sequenced as the virus thrives for a longer period in these cases. Poor immunity can render conditions conducive for favourable mutation and generate an even more lethal version. 

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The Omicron BF.7 variant has a very high R0 value of 10-18, which means a carrier can infect 10-18 persons. It is therefore advisable that India remains in a preventive mode and follows Covid-appropriate behaviour, especially in crowded places. Re-infections, especially among those already infected and with post-Covid complications, can lead to chronic disease including cardiac and kidney diseases and increase the risk of diabetes. 

‘Long Covid’ complications

Dr Ranjan noted that a high number of people suffer from post-Covid/long-Covid complications which increase the risk of diabetes, heart stroke and other vital organ malfunctions. “There is no need for panic yet, but we need to be alert and must follow Covid guidelines appropriately,” he said. 

An Omicron variant with rare mutations enabling it to escape immunity and infect at a more rapid pace emerged in late 2021 and has further evolved into multiple subvariants BA.5, XBB and BF.7. With further mutation in spike protein, they have evolved and can escape immunity gained through natural infection and vaccination or both. They can infect both recovered and vaccinated individuals and cause disease with varying degrees of severity. 

India’s edge vis-a-vis China

Currently, China is facing the worst Covid-19 situation in the last three years and the wave is driven by BF.7. This situation has arisen possibly because China still has a large population not infected because of its strict Covid-19 policy, low vaccination among vulnerable sections and also its ‘less effective’ vaccines.  BF.7 is causing severe disease among this population leading to mass hospitalisation and huge loss of lives. With China relaxing its Covid policy, it is highly likely that the situation will not improve in the near future, resulting in even more casualties as well, Dr Ranjan said. 

BF.7 has also been reported in other countries but the situation in terms of disease severity and hospitalisation is not so high. The nature of immunity of the Indian population is different from China: either acquired through natural infection or vaccination. This gives India an edge since it has seen huge infections in previous waves, helping build natural immunity and providing better protection against subvariants, including BF.7.