Covid is here to stay, we will have to adapt

THERE has been a surge in Covid cases in many parts of the country. India recorded nearly 13,000 new cases in a day, the highest in around eight months, while the active case burden increased to over 65,000, according to Union Health Ministry data updated on April 20. The numbers are rising in Delhi, Maharashtra, Rajasthan, Uttar Pradesh and Haryana.

India reported over 61,000 cases in the period between April 9 and 15, around 80 per cent up over the preceding week. A cause for worry is the increase in the number of deaths recently, though most of them have been of patients with prior comorbidities.

The recent uptick in Covid cases in India is due to a recombinant variant XBB and its descendants XBB.1.16 and XBB.1.5 — both sub-variants of Omicron. It is possible that XBB.1.16, also called Arcturus, may turn out to be the dominant variant in many parts of the world.

The World Health Organisation (WHO) has categorised it as a VUM (variant under monitoring). There is a concern about this variant as it has some mutations which can make it escape immune response of the host (human being). There is little information about it causing severe illness, but it is more transmissible and some reports suggest it to be causing red eyes (conjunctivitis) also. The prevalence of XBB.1.16 has increased from approximately 21 per cent in February to over 35 per cent in March.

There was a great scare in the last few months of 2022 with Covid cases rising rapidly in China because of the likelihood of spread to other countries. With international travel fully opened, there is free admixture of possible cases from different countries and the eventuality of development of new variants. Variants are modified viruses with one or more new mutations. Mutations are changes in genetic structure of an organism and occur naturally as the virus multiplies. The natural tendency of an organism is to acquire mutations which benefit it by making it more virulent or infectious.

Scientists keep track of emerging mutations and variants by genomic surveillance of selected samples from different states. The idea is to incorporate the new information into preventive and therapeutic strategies. We have already seen the havoc caused by the Delta and Omicron variants around the world and in India. The Delta Plus variant had increased transmissibility, stronger affinity for receptors in lung cells and immune escape property, making it evade protective response of the host. The new variant believed to be behind the recent upsurge in India is also being reported from other countries like the US, Australia and Singapore.

Irrespective of the emergence of new variants, the symptoms remain more or less the same — fever, cough, sore throat and body aches. There are minor variations, though, with change in incubation period or propensity to cause more severe disease with different variants.

Soon after identification of Covid-19 disease, the original strain of the virus, called Wuhan-1 or ancestral strain, was isolated and sequenced, paving way for the development of vaccines against it. All vaccines, including the mRNA (messenger RNA) vaccines (Pfizer-BioNTech and Moderna, USA; Gennova, India), the viral vector vaccines (AstraZeneca or Covishield in India and Johnson & Johnson in the US), inactivated whole virus vaccine (Covaxin) and others were designed to protect us from the disease caused by the ancestral strain. For SARS-CoV-2, primarily a mucosal disease affecting the respiratory system, the goal has been to protect against severe disease, hospitalisation and death, not to prevent infection.

As the virus spread and multiplied, it underwent a number of mutations and it was thought that the existing vaccines and therapies (monoclonal antibodies) may not be effective against the new strains. Scientists found that mRNA vaccines could be easily modified to counter the new strains and, thus, bivalent (effective against two strains) vaccines were engineered. These were supposed to protect against the ancestral strain as well the new variants. It was proposed that updated boosters could be given periodically to counter newer variants which might develop in the meantime, as is done for influenza virus with flu vaccine.

A recent article in the New England Journal of Medicine suggested that the bivalent vaccine and bivalent boosters provided only a modest extra benefit. Scientific data, so far, suggests that the Covid-19 variants haven’t evolved to escape the protection against severe disease, offered by vaccination against the ancestral strain or previous infection. In the coming years, we can expect pan-variant vaccines which will be effective against multiple strains and vaccines which can be administered through nasal inhalation or even a pill-based or skin-patch vaccine. All of this could perhaps remove vaccine hesitancy.

Is there a cause for alarm in India? Though a mathematical model has predicted cases climbing up to 50,000 by mid-May, most of the cases, so far, are mild and self-limiting. Patients who are elderly or those who have other concomitant diseases need to be cautious. It is advisable to take preventive measures and wear a mask, especially in crowded places. The question in everybody’s mind is to take a booster dose or not.

Over 220 crore vaccine doses have been administered since the beginning of vaccination two years ago, though less than 20 per cent of the vaccinated have received a booster shot. Additionally, with a large proportion of population getting protection following natural infection, there does not seem to be a cause for alarm presently. We, however, need data to see how long the protective efficacy of natural infection or vaccination or hybrid immunity lasts.

We must understand that SARS-CoV-2 virus is here to stay and we have to live with it. It is like other respiratory viruses which flare up periodically and cause severe disease in some individuals like the elderly or those on drugs that suppress immunity. Regarding the question of boosters, experts suggest that they are probably best reserved for the people most likely to need protection against severe disease — specifically older adults, people with multiple coexisting conditions such as cancer or diabetes, which put them at a higher risk for serious illness, and those who are immunocompromised.