The newest SARS-CoV-2 variant that may upset the relatively steady state of the present endemic prevalence of the Delta variant in India is the B.1.1.529. It was designated as a variant of concern (VOC) and named Omicron by the WHO on November 26. The variant was detected in the second week of November in South Africa. Since then, it has been detected in Israel (presumably imported from Malawi), Belgium (presumably from Egypt or Turkey), Hong Kong, the UK, Australia, Denmark and Holland (from South Africa) and Italy (from Mozambique).
The Omicron variant has over 30 mutations in the spike protein region that seem to confer two properties that render it worse than Delta. One, it is characterised by a very high viral load in infected people and consequently spreads faster. In Hong Kong, the viral spread was clearly airborne through aerosols generated by infected individuals shedding enormous quantities of the virus. Second, it infects people with vaccine-induced immunity that protects against other variants. In South Africa, it has spread to several persons who had previously received two doses of approved vaccines. This indicates that the virus may have antigenic drift worse than that of Alpha, Beta, Gamma and Delta variants. However, these preliminary assessments await confirmation. The large number of mutations plus the above two features were the reasons why WHO named it a variant of concern.
Thus, although genetically SARS-CoV-2, in its behaviour and potential for overcoming herd immunity, we must assume that it is a variant that may go around the world and possibly even replace the current predominant Delta variant. Unless we take immediate and important interventions, it can invade us very fast, with possible dire consequences. This is a red alert. The worst fear is the possibility of a third wave in India after the long lull of endemicity. Omicron does not seem to cause more severe disease than earlier variants, but it is too soon to be sure.
Our first defence is to prevent importation of the Omicron variant. The government was aware of this need, but instead of immediate action, the plan is to introduce strict screening of air passengers from December 1. In the interim, the variant could enter and spread. Will this delay turn out to be too little too late?
Air travellers arriving in India may be classified into three categories. All arrivals from the cluster of countries in Southern Africa are the first category. They must be subjected to the RT-PCR test on arrival, kept under strict quarantine for 72 hours, retested and released only if negative. The second test on the third day will detect those who had been infected but were tested too early and detection was missed. This would ensure that the inconvenience to uninfected travellers will be minimised to just three days. Those who are infected must stay in quarantine until their RT-PCR test turns negative.
The second category should consist of all travellers from other countries known to have been infected by Omicron. This list must be updated on a daily basis. The passengers must be tested on arrival and let free if negative with strict instructions for Covid-appropriate behaviour and a proviso that they will get retested three to four days later.
All international airports must be sufficiently staffed to collect samples and get tests done without any delay. Test results must be made available in the shortest possible time. A computerised system to track these individuals and record these events with easy access to all concerned has to be a public health priority. Those from non-infected countries constitute the third category. They carry none or minimal risk for Omicron importation and restrictions are unfair at this point. The current method of airport checking should be sufficient for now. They should report any Covid-like symptoms promptly to the designated authorities for immediate testing.
INSACOG, a consortium of 28 national laboratories to monitor the genomic variations in SARS-CoV-2, must ensure that all RT-PCR tests done in India will reliably detect the Omicron variant. It must also make sure that genotyping of all positive samples is done to detect the variant until clarity emerges on its altered properties and epidemiological consequences.
Although immune evasion (escape from previous vaccine-induced immunity) of VOCs is very unlikely, they acquire varying degrees of reduced susceptibility to vaccine-induced immunity. For now, we can assume that the high levels of immune response achieved from available vaccines will still protect us from severe illness caused by the breakthrough infection by Omicron, similar to the protection offered against the Delta variant. For achieving high-immunity levels, the current two dose schedule should be followed by a booster dose after a minimum of six months. There are recent reports of nursing and other students getting infected in clusters (presumably by the Delta variant) after rejoining in-person classes. This can get worse if the Omicron variant enters India.
So, our defence strategy calls for vaccinating all, including children, with two doses followed by booster doses after six months. Currently children are not eligible for vaccination by policy. However, confronted with the Omicron variant, and the need to protect our population, we should not leave out a segment to become a reservoir that amplifies and transmits the virus. It is in our national interest to expedite a policy shift and start vaccinating our children using certified vaccines.
National regulatory agencies and vaccine policymakers must consider these steps to be of utmost importance and urgency. The Union and state governments should urgently educate the public and set up systematic vaccination drives covering the urban areas first (at highest risk of spread from importations of Omicron variant) followed by the rural ones in a time-bound manner and on a war footing.
DR T Jacob John
Former Professor of Clinical Virology, CMC, Vellore
DR M S Seshadri
Medical Director, Thirumalai Mission Hospital, Ranipet
(tjacobjohn@yahoo.co.in, mandalam.seshadri@gmail com)