There may not be a third wave: Top virologist

A woman gets a shot at Wadia Hospital on Monday. Pic/Suresh Karkera

With the emergence of the Delta Plus variant in a few countries and its threat looming large over India, health experts and virologists have offered differing views on its likely impact. While some experts feel the contagious strain will target even vaccinated people and children, a top virologist says there are less chances of a third wave, though he insists that being prepared is always better.

A health worker takes a sample from a long-distance traveller at LTT on Monday. Pic/Sameer Markande

According to Dr Subhash Hira, Professor of Global Health at the University of Washington-Seattle, "Earlier on in 2020, genome analyses had shown global dominance of SARS-CoV-2 variants as D614G which was responsible for waves- 1 and wave-2 of SARS-CoV-2 worldwide and paved the way for an appropriate universal vaccine. However, towards the end of 2020, new and genetically distinct phylogenetic clusters of SARS-CoV-2 were identified globally; later designated as Variants of Concern (VOCs) and Variants of Interest (VOIs) by WHO."

Dr Hira said the World Health Organisation (WHO) has categorised the five important Variants of Concern (VOCs), which have higher transmissibility and can reduce the effectiveness of existing treatment and vaccines, as Alpha, Beta, Gamma, Lambda, and Delta. He said that the third wave in the UK and Israel showed that almost 80 per cent and 95 per cent of new infections were caused by the Delta variants, respectively.

"While D614G paved the way for universal vaccines, the sudden accumulation of mutations in new VOCs, such as the Delta (having 6-8 mutations) and Delta Plus (having over 36 mutations in its sequences) have led to reduced neutralisation by naturally or vaccine-elicited antibodies. The impact of the mutation clusters on re-infections and vaccine breakthrough infections caused due to reduced performance of different vaccines in terms of vaccine efficacy and neutralisation potential. The latter changes in the virus, coupled with the false sense of security of the host towards the vaccine to D614G strain and leading to lowering its guard to the barrier methods, are the bases of scientists who are expecting the third wave by August-September," said Dr Hira.

Dr Subhash Hira, Professor of Global Health at the University of Washington-Seattle

About the potential third wave, he said, "With the emergence of new variants, genomic surveillance has become a powerful tool to not only detect spread of the variants but also in understanding their infectivity. Genome sequencing of Covid-19 hot zones and animal reservoirs would be crucial for scientists and public health experts to prevent further epidemics. Slogans such as ‘We are not safe, until everyone is safe' as equitable vaccine distribution is a humanitarian imperative. Despite having a fully funded COVAX program, in developing countries, the health workers and people with underlying conditions will have no access to vaccines while only ten nations have administered 75% of all vaccines. This will lead to a disproportionate size of wave-3 depending on the vaccine penetration in a country."

Dr Hira also emphasised, "Neurological manifestations are now widely being recognized in Covid-19 patients infected with delta variants. A wide array of manifestations ranging from encephalopathy, insomnia, ageusia and Guillain-Barré syndrome have been reported. Alzheimer's disease-like cognitive impairment has also been linked with delta variants. Considering the role of VOCs in fuelling subsequent Covid-19 infection waves, it is imperative to pre-implement necessary measures in controlling the Covid-19 pandemic."

Doctors working in Covid-19 hospitals say the third wave might hit Mumbai in the next few weeks, citing the increase in number of cases and virulence load in the past few days.

Dr Rajesh Dhere, dean of Covid Jumbo Centre, BKC, said they have increased the capacity to 2,320 beds at their facility, including 100 beds for the pediatric ward, and 108 ICU beds. "From the pattern of Delta three variants in the UK and US, it has been found to be over 60 per cent more virulent. So, the only solution is to maintain and follow Covid-19 restrictions - wear a double mask, maintain social distance and hand wash."

Noted virologist differs

Well-known virologist Dr Jacob John from Vellore had a different take. He said, "Variants have different ‘transmission efficiencies' -- usually denoted by ‘basic reproduction number' (R0). The R0 of the ‘founder variant' (Wuhan virus with D614G mutation) was ~2, which means one infected person would transmit infection to only 2 among all non-immune social contacts. That was pretty low transmission efficiency. Delta variant has an R0 of 4-6 which means extremely high transmission efficiency."

Dr Rajesh Dere, dean of BKC Jumbo Centre said they've got more beds

In case of a higher R0, Dr John explained, the outbreak can be sustained by a smaller number of susceptible populations. "When infection spreads to more persons, children also get infected. Within families, the founder variant infected 3 out of ten household contacts whereas Delta infects 100 per cent. So, more children getting infected is a function of the virus' transmission efficiency," said John.

He added, "Since India's second wave was predominantly due to Delta, and as the wave is abating, the same virus cannot cause the third wave. If a variant with R0 more than 4-6 emerges, we will have a third wave, of low magnitude, with the same proportions of children infected in the second wave, but for a variant to better the R0 is very unlikely and for that reason a third wave is also very unlikely."

Stressing the need for expediting vaccination, he said, "The second wave is abating; if we can speed up vaccination, then even the natural susceptible people's number will shrink, further ensuring no third wave. Getting prepared is wise: expect the best, but be prepared for the worst."

Five
No. of important VOCs categorised by WHO