Delta - Delta Plus: Why we must ramp up COVID vaccination in a big way?

We need to assume that there may be a third wave in Manipur too. Even if that may turn out to be a wrong anticipation, it's better to err on the side of caution.


Representational Image (PHOTO: Pixabay)

 

CONTAGIOUS Delta Strain: The delta variant (B.1.617.2) is rapidly spreading across the globe and is now detected in more than 74 countries (HT, June 14, 2021). It's now the predominant varaint in the UK and now accounts for over 90 per cent of new cases in the UK. We need to be extremely careful about this variant as it's much more contagious than the alpha strain and extremely more transmissible than the original  SARS-2 coronavirus (SARS-CoV-2). This variant caused a surge of about 33,630 cases in just a week in the UK, prompting the government to postpone the planned easing of restriction from June 21 to July 19, 2021(TOI, June 18, 2021).

Why is delta so worrying? Because it's much more infectious than the alpha strain (B.1.1.7) by about 40-60 per cent. According to Dr Neil Ferguson, eminent epidemiologist based in Imperial College London (ICL), it's at least 60 per cent more contagious than the alpha variant (which itself is supposed to be 50 per cent more transmissible than the original Wuhan strain). A variant may become concerning if it's more infectious or induces vaccine escape or causes more serious disease. Data obtained so far indicates that the delta variant mayn't be causing more severe disease or higher fatalities but it's definitely leading to rapid increase in number of infections.

As Zeynep Tufekci says in NYT (New York Times, May 28), a variant with higher transmissibility poses much more danger to people not protected by either prior infections or vaccinations, even if the strain is no more deadly than earlier variants. He cites an example of a virus whose original reproduction rate was 3 (that is, an infected person can transmit it to 3 other persons) compared to a variant that now has the reproduction rate of 4. He calculated that, after just 10 generations, and starting with just 2 infected cases in both the scenarios, the former (R0= 3) would lead to 40,000 cases only while the latter (R0= 4) would lead to 524,000 infected cases, a whopping 13 times increase in the number of cases!

Delta Plus Variant

A new mutant of the delta strain has been found in the UK (India Today, June 14, 2021). It's named delta plus or AY.1 strain. It has acquired a new mutation besides those already present in the delta variant. The mutation K417N is present in the spike protein of the SARS-2 coronavirus. PHE found the new variant in 63 coronavirus genomes, of which 6 originated from India.

There's a preliminary thinking among researchers that the K417N mutation may increase the immune-escape potential of the variant. This means that delta plus may possibly increase the chances of reinfections in vaccinated individuals. However, more studies are needed to confirm this. As of now the delta plus variant (B.1.617.2.1), a sub-lineage of the delta strain (B.1.617.2) is classified just as a variant of interest (VoI) and not variant of concern (VoC). 

One concerning property of the delta plus variant is that the Roche mAb cocktail (casirivimab and imdevimab) used to treat mild-to-moderate COVID cases seem to work less effectively against the delta plus strain.

WHO has recently launched a new nomenclature for the SARS-CoV-2 variants of concern (VoC) and variants of interest (VoI) circulating across the globe. A coronavirus mutant is called a VoC if it has one or more properties of increased transmission, enhanced tendency to cause severe disease, reduced detection in diagnostic tests, higher resistance to currently used vaccines, increased tendency to develop vaccine-escape variants etc. If the variant lacks these properties, it would be dubbed simply as VoI.

Other SARS-2 Strains

Lambda is a new variant which was first detected in Peru. As of now, it's dubbed as only a variant of interest. However, deeper analysis is required to establish if this variant has higher transmissibility.

This variant is now prevalent in 29 countries, mostly in Latin America. e.g. Peru. Argentina and Chile etc. WHO says it was first identified in Peru, where 81 per cent of the cases since April 2021 were associated with this variant (dnaindia.com, June 19, 2021; indiatvnews.com, June 19, 2021). In Chile, it accounted for 32 per cent of all submitted sequences in the last 60 days; there, it was only outclassed by the gamma variant (P.1 strain), first identified in Brazil. Other countries including Argentina and Ecuador are also reporting increased prevalence of the lambda variant.

However, as there is as yet no conclusive data about its increased infectivity or potential for causing more severe disease or vaccine resistance, WHO is still classifying this variant as a variant of interest (VoI).

Why Vaccination Matters?

In view of the raging delta variant and possible rise of other highly infectious variants, the role of vaccinations (full dosage) is very critical. Let's look at an instructive piece of news. As reported in TOIJune 18, 2021, a total of 806 people were hospitalized with delta variant infections in the UK as of June 14, 2021. Of these, 527 were unvaccinated individuals compared to just 84, which were fully vaccinated i.e. thos who got both jabs). So, one can easily conclude that vaccinations protect against hospitalisations and possible death, if not infections altogether.

There are also hints that the delta variant may lead to more hospitalisations compared to other strains. It may also be more resistant to the currently used vaccines, especially after just a single dose. As per PHE's study, both Pfizer and AstraZeneca vaccines provide 33 per cent protection against the delta variant after a single jab. After, both doses, Pfizer vaccine imparts 88 per cent protection compared to 60 per cent by AstraZeneca vaccine.

Vaccines in the Pipeline

In addition to CoviShield and Covaxin, there are many other vaccines in the pipeline for production in India (TOI, June 19, 2021). These includeCorbevexandPTX-COVID19-Bof Biological E company,ZyCOV-Dof Zydus Cadila,Sputnik-Vto be produced by Dr Reddy's Labs, and several other vaccines in various stages of development.

Of these, Corbevex is touted as the most economical vaccine in the world. It's to be priced at about Rs. 50  per shot. It's also one of a kind vaccine; a 'recombinant protein subunit' vaccine.

Novavax, a US-based firm, recently released data claiming that its vaccine has an efficacy of 90.4 against COVID-19 and 100 per cent efficacy in protection from severe COVID disease. It may soon obtain EUA for release in US. It's a recombinant nanoparticle protein-based vaccine and is code-named NVX-CoV2373. It's one of the very few vaccines to undergo phase 3 clinical trials when VoCs such as alpha (B.1.1.7) and beta (B.1.351) were prevalent in the population, It's expected that this vaccine may also be highly effective agianst the currently raging delta strain of SARS-CoV-2.

Clinical trials also in progress in India. Serum Institute of India (SII) is going to manufacture this vaccine as Covovax (Indian version of Novavax vaccine). This will be the second vaccine to be made by SII in India, after CoviShield.

Strategies for the third wave

Certain measures would help prevent, ward off, or mitigate the third wave. One is to massivelyspeed up vaccinations. Another isaggressive genomic surveillanceto monitor the trajectory of delta and other COVID variants across the country to ascertain which variant is surging where and catch any new variant early before it leads to a deadly local outbreak. R. Sukumar, Editor-in-Chief,Hindustan Timeshas another two interesting suggestions (HT, June 3, 2021). One is to link thestringency of standard SOPs(3 Ms, 3 Ws, as mentioned in previous columns) in a district to the ratio of the population that has been vaccinated. Another is about decidingwhen and where to ease to ease lockdowns; he suggests a possible benchmark: five per cent positivity rate or less for two weekscombined withvaccine coverage of a minimum of 20 per cent of eligible population(18 years and above) to permit easing of restrictions in any locality.

Possible measures for Manipur

We need to assume that there may be a third wave in Manipur too. Even if that may turn out to be a wrong anticipation, it's better to err on the side of caution. Accordingly, we must initiate measures to squarely face a possible third wave in our state.

These may include:

  • Speeding up vaccinations in a big way.
  • Genomic sequencing of a subset of positive cases and surveillance of the variants including the delta variant: which COVID strains are there in Manipur, where are they, and where are they moving towards.
  • Boosting up healthcare provisions such as medical oxygen plants, tankers and cylinders; steroids, antifungal drugs, oxygen concentrators, ventilators, oximeters, masks, PPEs, sanitizers etc.
  • Strengthening of healthcare infrastructure such as construction of new COVID hospitals.
  • Provision of more COVID care centres (CCCs), more Covid beds and ICUs in existing hospitals
  • Constitution of a special taskforce for the third wave; a separate taskforce for pediatric COVID is also highly recommended.
  • Special provisions for kids such as pediatric hospitals, wards, and ICUs, pediatric oximeters, concentrators, and ventilators and strengthening of staff such as pediatricians and pediatric nurses and paramedical workers etc.

As an editorial in the prestigious medical journal, The Lancet Microbe(Jan. 1, 2021) says, "Vaccines will be instrumental in the control of COVID-19, but their global distribution will be challenging and their effect won't be immediate." So, in the meantime, we must not let our guards down and we must still strictly observe the non-pharmaceutical interventions such as the major SOPs of theuse of face masks, physical distancing, and hand hygieneandavoidance of 3 Cs:crowded places, close contact settings, andclosed spaces(with poor ventilation).We must religiously follow the protocol of'test, track, and treat'for months to come. If possible, the public health authorities must take steps to prevent large gatherings such as weddings and death ceremonies, music concerts, and large meetings. The 'hoi polloi' must voluntarily practice the3 Ws(watch your distance, wear your masks, wash your hands frequently) and avoidthe 3 Cs:crowded places, closed contact settings, and closed spaces.

Meanwhile, we must enhance the pace of vaccinations across India, including Manipur, in a big way. In this intricate games of chess, humanity must be one step ahead of the wily virus!

(The views expressed are the writer's own)

First Published:June 20, 2021, 1:07 a.m.

Leave a comment