Covid vaccines & the Omicron era

Global data shows two doses are essential for protection from disease and booster protects further from symptomatic infection. While we await local data, let us not delay preparing for boosters and vaccinating children

This has raised concern, especially since England has so far given two doses to about 70% and a booster dose to about 35% of its population.
This has raised concern, especially since England has so far given two doses to about 70% and a booster dose to about 35% of its population.

By Shahid Jameel

A new variant of the COVID-19 virus, named Omicron, has taken the world by storm ever since it was reported by South Africa on November 24, with the earliest sample dating back to November 9. Since then, it has been detected in 77 countries, showing local transmission in many and spreading rapidly. New modelling studies suggest 25,000 to 75,000 deaths in England by the end of April 2022. This has raised concern, especially since England has so far given two doses to about 70% and a booster dose to about 35% of its population.

What do we know about the Omicron variant? It has by far the highest numbers of mutations of any other variant—50 in all when compared to the original Wuhan virus. Of these, 32 make changes to the spike protein that covers the virus’s surface, and 10 are in a region of this protein that promotes virus entry into our cells. Several of these mutations are found in other variants as well, but never came together in a single variant earlier. How do these changes alter the phenotype (behaviour) of the virus?

Data from South Africa and several European countries show a doubling rate of 2-3 days. A UK report shows its transmission in a household setting to be 3-fold higher than Delta. Such rates can lead to an exponential rise in cases. But the good news is we know how to reduce spread with mitigation measures such as masks, ventilation, avoiding crowds, etc. Another good news is that wherever Omicron is gathering steam, the proportion of people with severe disease is lower than expected. A large study by Discovery Health, South Africa’s largest health insurer, released on December 14 showed the risk of hospitalisation among adults who contracted Covid-19 to be 29% lower.

Researchers from the University of Hong Kong reported on December 15 that Omicron infects and multiplies 70 times faster than the Delta variant in the human airway, but infection in the lung is significantly lower. This could explain why Omicron transmits faster between humans but shows reduced disease severity.

Several laboratory studies have shown sera from people who had prior infection or vaccination or a combination, to poorly neutralise the Omicron variant. First readouts on effectiveness of the Pfizer vaccine show that over 5 months it drops to 60% against Delta and about 34% against Omicron. A booster dose makes the vaccine 95% effective against Delta and about 75% against Omicron. This translates to about 5 times more breakthrough infections by Omicron compared to Delta.

Where does India stand? By July 2021, the 4th National Serosurvey estimated 67.6% Indians to have antibodies. Considering that the vaccinated fraction was very low by then, much of it came from infection. Despite an impressive delivery of 1.3 billion doses, only 38% Indians have received two doses and 59% have received one dose. Global data shows that people with prior infection with other variants have minimal capacity to neutralise Omicron. This together with past experience and demography suggests that there may be rapid expansion of symptomatic infections in India over the coming weeks. While hospitalisations may remain lower than in the earlier waves, even a small fraction of a very large number is a large number. It is therefore prudent to keep hospital capacity ready and ensure adequate stocks of medicines, oxygen, etc.

India must also increase the pace of its vaccination to cover as many people with two doses as possible. Reducing the gap between two doses of Covishield from 16 weeks to 12 weeks will speed this up. Though it is unlikely to stop symptomatic infection, a combination of prior infection and vaccination in a large fraction of adults will ensure low rates of severe disease, hospitalisation and mortality. Simultaneously, India should urgently formulate clear policies on vaccine boosters and vaccinating children. What vaccines can be used, how many doses would be needed, when should these be given and who should be prioritised?

About 90% doses given in India are of Covishield, which would not work well as a booster dose in people who have already received two doses of it. What are the other options? Covaxin can be used as a booster for people vaccinated with two doses of Covishield and vice versa. The DNA vaccine ZyCoV-D can also be used. There are two protein vaccines available to India that will work well as boosters. Covovax, manufactured by the Serum Institute of India for Novavax (USA), has completed phase 3 trials, and is approved in Indonesia, and SII has exported 50 million doses. Corbevax-E is manufactured by Hyderabad-based Biologicals E in partnership with Baylor College of Medicine and Dynavax Technologies (USA). Both vaccines await emergency use approval in India.

A policy for boosters, like everything else, should be based on evidence not emotion. Global data shows two doses are essential for protection from disease and booster protects further from symptomatic infection. While we await local data, let us not delay preparing for boosters and vaccinating children. Indians are not exclusive. This is one lesson we have learned painfully over the past year.

Fellow, OCIS and Green Templeton College, University of Oxford, UK, and visiting professor, Ashoka University, India

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