Health
Explained | Understanding the Omicron variant of coronavirus
The story so far: With the highly transmissive Omicron variant now recorded in most States, and given the mild symptoms seen in people who are fully vaccinated, the Indian Council of Medical Research (ICMR) has issued a revised testing strategy advisory on January 10. The new advisory replaces the one last issued on September 4, 2020.
The previous advisory was for routine surveillance in containment and non-containment zones, and hospital settings. Thus, the advisory was for detecting cases immaterial of their symptom status. In contrast, the scope of the latest strategy is more for isolation and quick care of high-risk individuals. While the September 2020 strategy included testing asymptomatic high-risk people, the latest strategy is for testing only individuals who show symptoms unless they are at risk because of being in contact with lab confirmed cases.
Besides testing all individuals showing symptoms, the September 2020 testing strategy called for testing all asymptomatic individuals who belonged to the high-risk category such as people older than 65 years and those with comorbidities whether they had come in contact or not with lab confirmed cases in containment zones. In the case of non-containment zones, the testing strategy of September 2020 called for testing people symptomatic with influenza-like illness (ILI), individuals with travel history and those in contact with laboratory-confirmed cases.
More importantly, the September 2020 advisory had a provision of testing on demand for “all individuals who wish to get themselves tested”. The latest advisory of January 2022, has removed the testing on demand provision. It also says contacts of confirmed cases of COVID-19 unless identified as high risk based on age or comorbidities do not need a test. The September 2020 and January 2022 advisories have clearly stated that testing is not required prior to discharge from a COVID-19 facility after clinical recovery. But the January 2022 advisory goes a step further by stating that testing is not needed prior to discharge from home isolation either.
With full vaccination coverage reaching 64.5% and a single dose of the vaccine administered being at 89.5%, hospitalisation rates have dropped. With 67% of people showing sero positivity in the last sero survery, and increased vaccine coverage since then, a significant percentage of the population has acquired protection either through infection and/or vaccination. In a majority of cases, the Omicron variant is asymptomatic or causes only mild symptoms in fully vaccinated people, particularly in those who do not belong to any of the high-risk groups. This has led to reduced hospitalisation for now. The current focus is not on detecting all cases. The reasons: despite test on demand, a vast majority of infected people have not been detected, as the last sero survey had revealed, and testing capacity might get stretched as the Omicron variant spreads very quickly.
The restrictive testing will result in further reduction in the number of people getting tested. This in turn will result in a lower number of cases being reported. If universal testing failed to capture a large fraction of infected cases as revealed in the sero surveys, the current strategy will make it even worse. States with higher integrity in testing and reporting cases had missed detecting relatively fewer cases per 100. With the latest testing advisory, India will report fewer cases thus not revealing the actual spread of the virus.
With limited capacity to sequence the genome, the actual scale of spread of the Omicron variant is already not known. As on January 16, only 8,209 Omicron cases have been reported in India. This is a gross underreporting given Omicron’s high transmissibility. Lower number of cases reported due to restrictive testing will lead to a false sense of security and prompt people to drop their guard. With the actual spread of the virus not known, States will find it difficult to deploy containment and mitigation strategies.
There is an argument that testing asymptomatic people will further stretch the testing system. But intelligent use of rapid antigen tests along with RT-PCR for testing symptomatic people will sharply reduce the burden on testing labs. The need for continued expansion of testing capabilities cannot be overemphasised, say experts.
Besides symptomatic individuals, the latest advisory restricts testing to only at risk (those older than 60 years and people with comorbidities) contacts of lab confirmed cases. The latest protocol thus takes it for granted that community spread is absent. The advisory not to test asymptomatic people overlooks the danger of such individuals spreading the virus to the vulnerable population, and children who are still not eligible for a vaccine. Even if the treatment protocol remains the same immaterial of the testing protocol adopted, understanding the rate of breakthrough infections, particularly with the Omicron variant, will be severely hampered by the restrictive testing strategy now in place. There is no data on fully vaccinated people being hospitalised, which makes evidence-based decisions difficult for the booster rollout for other age groups.
Rapid antigen tests will surely reduce the burden faced by RT-PCR testing labs. But the sensitivity of rapid antigen tests is low and thus have higher chances of returning false negative test results. Though symptomatic individuals with a negative antigen test result are required to undergo a RT-PCR test, past experience suggests that this will not be followed in practice. But even when rapid antigen test results done at home come out positive, it has come to light that such results are not reported to authorities and hence go unrecorded. Maharashtra is taking steps to address this problem in the city of Mumbai.
