Curbs delay, but don't prevent Omicron spread: Study

The study suggests that Omicron eventually spreads and affects nearly as much of the population as it would have without the restrictions

Validating the government’s decision to lift night curfew from Monday and to reopen schools, a case study of Bengaluru Urban on the impact of daily night and weekend curfews concluded that the restrictions, at best, slow and delay the spread of the Omicron variant of the coronavirus.

The study, using mobility data published by Google, suggests that Omicron eventually spreads and affects nearly as much of the population as it would have without the restrictions.

Also, if Karnataka’s case trajectory follows the South African Omicron wave trend and the hospitalisation is similar to that observed in well-vaccinated countries (2% of the confirmed cases), then the healthcare requirement is likely within the capacity of Bengaluru Urban when the caseload peaks, with or without mobility restrictions.

Authored by eight researchers from the Indian Statistical Institute (ISI), Bengaluru Centre; Centre for Networked Intelligence, Indian Institute of Science (IISc) and the Biocomplexity Institute, University of Virginia, the study was published on the pre-print server medRxiv on January 26.

Two of the authors, Prof Siva Athreya from ISI and Prof Rajesh Sundaresan from IISc who recently made Omicron projections for the third wave’s peak in Karnataka, were also part of the research team for this study.

The Karnataka government imposed weeknight and weekend curfews starting the night of January 7.

The corresponding author of the paper, Prof Athreya observes, “Even if Karnataka case trajectory follows both the South African Omicron wave trend and the hospitalisation requirement observed there (6.9%), then the healthcare capacity may be exceeded at peak, with or without the mobility restrictions.”

Since the start of the pandemic, Google has been publishing community mobility reports that indicate the level of activity in various interaction spaces like retail, recreation, grocery, pharmacy, parks, transit, workplace and residential areas.

The researchers extracted information from the report of January 15 and plotted the mobility factors for each day of the week. It summarises the mobility level in the two weeks of January 2022 with respect to the average level in December 2021.

In the two weeks of January starting January 1, 2022, the first week does not have mobility restrictions whereas the second week has mobility restrictions. The researchers assume a 20% reduction in mobility in this study on account of the restrictions. Duration of time spent in the residential areas was seen to have increased by 9-13% over the weekend.

The researchers consider the base case scenario as one with no mobility restrictions and the other scenario is when mobility is restricted until March 31, 2022. They specifically compare case projections at the end of January, February, and March 2022.

“The pattern of weeknight and weekend curfew, followed by relaxations during the weekday, seems, at best, to slow and delay the Omicron spread. The simulation outcomes suggest that Omicron eventually spreads across the population,” the
paper said.

When mobility restrictions are in force until March 2022, the reduction in the peak cases is 9,399 (if 30% population susceptibility is assumed) and 18,326 (with 60% susceptibility).

“Since the peak is expected in the third week of January 2022, the usefulness of the restrictions beyond the peak is limited,” the paper concludes.

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