01 Dec , 2021 By : monika singh
India is likely to have much more hybrid immunity than other nations against the heavily mutated Omicron. However, this, too, may not hold, if the immune escape is very high, said Anurag Agrawal, chair, WHO's technical advisory group on SARS-CoV-2 virus evolution, in an interview to Teena Thacker and Vikas Dandekar. Edited excerpts:
How worried should India be, given the density of population?
On one side we have density-associated risks of fast transmission; on another we have hybrid immunity - infection and recovery followed by vaccination. With over 2/3rd of the population previously infected, mostly after the huge second wave, and a large vaccination drive afterwards, India is likely to have much more hybrid immunity than other nations. Such immunity is stronger than natural or vaccine-induced immunity. However, this too may not hold if the immune escape is very high. The key question then is severity, and as of now, we do not know. I always think that it is better to do a continuous risk assessment and prepare than to worry. We have time right now and getting public health measures in place will mitigate the risks.
How soon can we determine the key data related to Omicron - like transmissibility and severity?
It should become clearer in a few weeks. Understanding severity will take longer than transmissibility, since it is likely to vary a lot by demographics, vaccination levels, types of vaccines, prior infections, availability of advanced therapeutics like monoclonals, etc.
How prepared is our genome surveillance to detect the mutation in India?
I don't see any issue with genome surveillance, but it only informs public health measures when done fast enough to make a difference. Logistics consume more time than actual sequencing and I think that is a very solvable issue. Personally, given the global seeding, we should just assume that it has arrived in India as well, and focus on rapidly identifying and sequencing clusters, as well as possible seeds such as infected travellers from high-risk countries.
You have also dismissed the claim that Omicron is six times more transmissible than Delta. Can you share more on what is the best way to assess the real data?
Right now, the situation is that there is high immunity to Delta in many communities due to large Delta waves. In this situation, a variant that is less transmissible, but very good at escaping immunity, can propagate much faster than Delta. This leads to probably wrong estimates, like six-fold higher transmissibility, by those who have just looked at the rate of replacement of Delta by Omicron. Secondary attack rate is a good way to assess transmissibility and data is awaited. Based on available data, even if Omicron is fundamentally more transmissible, it is unlikely to be by very much.
Since the RT-PCR for the S protein comes up negative, do you think we should add more tests?
Most kits in India are 2-gene and do not use S gene, so false negative is not a problem. The use of 3-gene PCR tests with one primer set covering the S-gene mutations that can either use a negative or a positive result to give a quick initial screen for Omicron is a good idea.