Hybrid immunity can stand us in good stead

Covid has returned yet again in a new variant called BF.7. It is a sub-variant of Omicron, which had affected the majority of our population earlier this year. The Central and state governments have started assessing the situation through high-level meetings and cautioned people to follow Covid-appropriate measures in the wake of increasing Covid cases globally, especially in China, Japan, South Korea and some Latin American countries. But the question on everyone’s mind is whether India be worried about this new variant.

In India, the Omicron variant has already caused the third wave, which began at the end of last year and lasted till early this year. The government had advised everyone to get the ‘precaution dose’ or booster shot to protect oneself from the Omicron variant. According to the government records, nearly 30 per cent people have already taken the precaution dose. The majority of the population has taken the first two shots and others have some level of immunity against the virus variants through natural infection. This situation is hugely different from that in March 2020, when the pandemic had begun and we had no idea what to do.

Since then, India has attained herd immunity or hybrid immunity, which is acquired from vaccination as well as exposure to the virus. The third wave was not as severe as was feared. Most of the cases were asymptomatic or mildly symptomatic, and severity was mostly limited to the people with comorbidities and compromised immunity. It appears that although the Omicron had nearly 70 times higher infectivity rate than the previous strain, Delta, which drove the second wave in India, it did not cause much severity. In mid-January, as observed through genome sequencing, the Omicron variant was found in more than 90 per cent of the Covid samples tested in Delhi. This shows that our population has already got exposed to the Omicron variant, and, thus, is equipped better against the BF.7 sub-lineage of Omicron.

The question is: why it is causing havoc in China? The reason is China’s ‘zero-Covid’ policy, which restricted people from moving out by imposing a strict lockdown in cities where even a single case was reported. The Chinese government had imposed measures like contact tracing, mass testing of population in a given locality, quarantine and lockdown to prevent the spread of the virus.

Researchers have suggested that China’s indigenous vaccine Sinovac, produced by Sinopharm, which was administered to Chinese people, gave low protection against the new variants. The combined effect of these measures resulted in low overall immunity of the Chinese population against the new sub-lineage of Omicron BF.7.

How has the virus mutated and progressed in the past nearly three years? The original virus was identified in China in December 2019, which mutated and gave rise to Alpha mutant in 2020 in the UK. Later, the Beta (B.1.135) variant was identified in October 2020 in South Africa. The Gamma variant, known as P.1, was first detected by Japan’s National Institute of Infectious Diseases on January 6, 2021, in a few people who had travelled to Brazil.

The Delta variant (B.1.617.2) was first detected in India in late 2020 and caused havoc during the second wave in India in the summer of 2021. This virus strain had high transmissibility and spread quickly around the globe. Next came the Omicron variant (B.1.1.529), named as BA.1 for simplicity, which was first identified in Botswana and quickly spread to become the predominant variant globally. It developed several sub-variants like BA.2, BA.3, BA.4, BA.5 etc. The BA.5 had developed two sub-variants namely BQ.1 and BQ.1.1 in October 2022. The latest sub-variant BF.7 is of BA.5 lineage.

All these variants and sub-variants develop due to mutation, a process where the bases in their genome change due to an error during replication. This change leads to alteration in the spike protein against which antibodies have been made by our system to kill the virus effectively. But the mutation-led change in the virus protein decreases the efficacy of the antibodies and virus escapes the immune system and infects more and more people.

Furthermore, a new intranasal Covid vaccine, iNCOVACC, made by Bharat Biotech, has also been approved. It is a non-invasive and needle-free vaccine and is available on the CoWIN app. Since the Omicron sub-variants are mostly localised in the upper respiratory system, this nasal vaccine will be very effective in preventing the infection and its spread.

The BF.7 variant was identified in India in September 2022 in Gujarat and Odisha, and despite the laxity in Covid-related guidelines at that time, these cases remained isolated and got cured. Even if sub-variant BF.7 spreads in our population, its impact is likely to remain low owing to the hybrid immunity acquired from natural infection and full vaccination. The Lancet recently reported that hybrid immunity against Covid has been able to diminish hospitalisation and deaths.

Despite having herd immunity and a majority of the population vaccinated, including the booster dose in one-third of the population, we cannot be complacent. Experience from the past waves tells us that we should be vigilant and should not lower our guard. At the individual level, one should use good-quality masks that properly cover the nose and the mouth, avoid large gatherings and get the booster dose. Watch out for symptoms such as runny nose, sore throat, fever, cough, vomiting, diarrhoea, body pain, lethargy and exhaustion. If having these signs, one should get tested and isolate oneself or take proper hospital care in the guidance of a doctor.

The authorities have alerted the people that the pandemic is not over as yet and Covid-appropriate behaviour is necessary to prevent it from spreading. The government should reassess the oxygen stock and the availability of the medicines and hospital beds. After assessing the situation, Covid-appropriate guidelines should be enforced. Random testing of travellers, especially those from the affected countries, is now being done on arrival. The government has also ordered genome sequencing of Covid-positive cases to assess the spread of BF.7. Witnessing the upsurge in China, the Centre and state governments have swiftly come into action. It shows that the authorities are now better prepared, which is a good omen.