After what seems to be a fairly quiescent period, India is witnessing a perceptible surge in new cases of Covid19, most of these from Kerala and Maharashtra. The June 13 release notified 8084 new cases of Covid-19 that were recorded in the last 24 hours. The cumulative active caseload is currently 47,995. While this may not seem very alarming, the detection of BA.4 and BA.5 and some sub-variants of BA.2 from states such as Maharashtra and Tamil Nadu should ring a bell of caution. The global evidence so far is that these are neither associated with new symptoms nor more severe disease. As the majority of mutations are similar to those found in other Omicron lineages, this is not unexpected; it requires close clinical and epidemiological monitoring, though. The markers to be watched out for are complications, hospitalisation and deaths.
Why are the numbers gaining momentum again?
The surge is most likely on account of the emergence of new sub-variants. Both BA.4 and BA.5 were first detected in South Africa, a country that performs genetic sequencing on a very large scale. BA.4 was first picked up in Limpopo, the northernmost province and relatively sparsely populated; many of the other variants were earlier detected in the highly urbanised parts of the country, though. BA.5 was first detected on February 25, 2022, in KwaZulu-Natal in northeastern South Africa. Both these have since spread to all South African provinces, signifying their potential for rapid spread, particularly in the backdrop of the recent widespread Omicron infection in the country.
In South Africa, the percentage of BA.4 sequences has grown from less than one per cent in January 2022 to more than 35 per cent by end-April 2022. The percentage of BA.5 sequences stood at 20 per cent by the end of April. This pattern suggests that these variants are more transmissible than the existing Omicron variant, or it could be the result of waning immunity from past infection or vaccination. While sharing many of the mutations as the original Omicron variant, BA.4 and BA.5 (mutations in their spike protein gene are identical) possess additional mutations too. These include L452R (detected in the Delta variant) and F486V mutations; both these may partially evade the immune response and lead to greater spread.
XE is a recombinant of both sub-variants (BA.1 and BA.2) of Omicron. It is circulating in at least eight different countries, including China, Hong Kong, South Korea, the UK and Germany. The Indian SARS-CoV2 Genomics Sequencing Consortium (INSACOG) confirmed the country's first case of Omicron sub-variant XE in early May 2022.
New mutations can be expected as SARS-CoV-2 continues to evolve. Such mutations shall be epidemiologically significant if they enhance the severity of the disease or are substantially able to overcome the immunity provided by vaccines or previous infection, or render diagnostic tests less effective, making it harder to control the spread of the disease.
Does this portend the fourth wave?
South Africa exited the fourth wave in January on account of Omicron, and health authorities there have warned of a possible fifth wave of infections driven by the BA.4 and BA.5 Omicron sub-variants. India may similarly experience another surge or fourth wave following the Omicron-led third wave. However, coverage of India's adults with two doses of vaccine is much higher than that of South Africa. Nevertheless, the emerging evidence suggests that the immune-escape characteristics – the ability to evade pre-existing immunity on account of vaccine or a previous infection – while not as dramatic as Omicron, may still lead to an infection wave. The evidence shall, of course, be dependent on how widely testing occurs, particularly given that much of the clinical picture will be of a mild nature with minimal hospitalisation. Put simply, while there may be a surge of infections, previous infection and vaccination shall almost certainly protect against the risk of developing severe Covid19 disease.
How well are we doing with boosters?
The vaccination drive in India, following its significant success with 96.3 per cent of those above 15 years receiving at least one dose and 86.3 per cent receiving both doses, needs to be sustained in terms of the uptake of boosters which has not been very encouraging till date. A month earlier, only about 2.1 per cent of the total population of India had received a booster dose
when the global average was about 25 per cent. The World Health Organization's (WHO) chief scientist Soumya Swaminathan has emphasised the importance of booster shots, especially for vulnerable groups. The Har Ghar Dastak 2.0 campaign is currently in operation from June 1 to July 31 2022. This mission mode campaign is designed to address sub-optimal coverage of persons aged ≥60 years with precaution dose, along with the considerably slower speed of coverage in the 12-14 years cohort, as well as reach the under-reached groups such as old age homes, out-of-school children, those residing in prisons or migrant groups in brick kilns.
The next steps
Much of the success in our journey ahead will be based on how effectively India is able to deal with the emergence and spread of new variants. The mantra: variants: keep searching for variants, aim for universal vaccination and focus on booster shots. The Indian SARS-CoV-2 Genomics Consortium (INSACOG) is tasked with this. It needs to be able to keep performing efficiently and make early sense of detecting variants and correlating with the spectrum of clinical symptoms and signs.
(The writer is Chairperson at the Centre of Social Medicine & Community Health, Jawaharlal Nehru University, New Delhi)
Disclaimer: The views expressed above are the author's own. They do not necessarily reflect the views of DH.