Puzzle out how to make vax ring-fences succeed
PremiumThe idea of vaccination rings to snuff out covid flare-ups needs a fair chance. It’ll take some math on infection versus immunity, but don’t let this strategy stumble on lousy input data
Our deadly second wave of covid has been ebbing for two months, but the number of daily infections continues to stay worryingly high. India reported an average of more than 42,000 daily new cases over the past week, about a tenth of our 6 May peak of over 414,000. We are still losing hundreds of lives everyday to the pandemic. With curbs on social and economic activity mostly lifted, people are observed to have thrown caution to the wind, swarming holiday spots and converging in public squares, a sight that “frightened" Balram Bhargava, who heads the Indian Council of Medical Research, for good reason. While covid fatigue is understandable, such careless crowding could set off a third surge that epidemic experts have warned of. While a ‘wave’ is what data graphs show, evoking a shape we usually associate with water, perhaps a more useful metaphor can be found in fire. Crowds are incendiary. And, once lit, a blaze is difficult to snuff out. What does or does not flare out of control could depend on the flammability of what flickers up. Like our immunity, that varies widely, and moving the needle on this variable of vulnerability is the task of vaccination.
The public immunization programme underway that aims to cover all adults is important, though it needs twice the pace of its daily rate of just over 4 million jabs recorded over the past week or so. What could also keep contagion down, however, is a parallel initiative that goes by a strategy of micro-targeted shots to contain flare-ups within geographical hotspots. As one report suggests, this is exactly what the Centre has in mind. New Delhi has written to states asking them to carry out “ring vaccination" around districts where over a tenth of all covid tests are showing up positive. This will involve identifying high-case zones for people to be vaccinated on priority within a wide radius of each outbreak; encircled by covid-resistant folks, the virus will not be able to spread too far in any direction. Such a ring-fence seems modelled on what’s done in some countries to contain forest fires: trees are felled and an inert ‘moat’ laid around a wild inferno so that its flames get no further.
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For the idea of a vax ring to be tried out, we will need to make not only special vaccine allotments, but also close calculations of how large a circle to vaccinate. The speed of every flare-up will have to be worked out properly and weighed against the generation of antibodies. As the latter is a far slower process, we may need to reduce the gap between doses. Clearly, much plotting and planning would be needed to optimize the effort. Since ring-fences require reliable information, their success would also depend on the accuracy of our approach. At last count, India had 73 districts with a covid positivity rate of 10% plus, over three-fifths in the northeast and several in Kerala. Express vaccines should be despatched to these places. Scanty testing across India, though, could yet knock us off target. A diagnostic scale-up will help, no doubt, but we must also try to minimize the ‘image’ incentive for states to undercount cases. Ideally, we need corroborative sources of data, too. Analysis of all-India data gathered by our Aarogya Setu app was supposed to offer us early alerts of local outbreaks, but has failed to live up to that promise. Perhaps if we rework this digital tracker, it could still serve as a useful smoke detector, even if it issues a few false alarms.
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