In May, the WHO tagged B.1.617.2 strain as the 'Delta' variant of SARS-CoV-2. The variant was identified as one of the drivers of the second wave of coronavirus infections that devastated parts of the country earlier this year.
The 'Delta' variant has further mutated to form the 'Delta plus' or 'AY.1' variant. However, there is no immediate cause for concern in India as its incidence in the country is still low, scientists said.
he new Delta plus variant has been formed due to a mutation in the Delta or B.1.617.2 variant, first identified in India and one of the drivers of the deadly second wave. Though there is no indication yet of the severity of the disease due to the new variant, Delta plus is resistant to the monoclonal antibody cocktail treatment for Covid-19 recently authorised in India.
According to Public Health England, 63 genomes of Delta (B.1.617.2) with the new K417N mutation have been identified so far on the global science initiative GISAID.
Here’s all we know about Delta plus variant of Covid-19:
What is this new variant?
Like all other RNA viruses, mutations arise naturally in SARS-CoV-2 as well when the virus replicates. Thousands of mutations have already happened, but only a very small minority are likely to be important and change the virus in terms of infectiousness or danger. Delta plus variant is the sub-lineage of the ‘delta variant’ which was first identified in India, which has acquired an additional spike protein mutation namely K417N.
What was peculiar about the Delta Variant that is important for us to predict the Delta plus variant?
The delta variant is 60 to 100% more infectious than the Alpha variant (earlier called the UK strain), and was responsible for the disastrous second wave in India. It has rapidly spread to over 80 countries including UK where it is now responsible for 99 per cent of the cases.
The Delta variant is also possibly more deadly. The death rate in the second wave was more than the first wave in India. Scotland researchers discussed in a recently published study (Lancet, one of the most prestigious medical journals) that the risk of hospital admission was approximately double in Covid patients with the Delta variant, compared Alpha strain.
Where has the Delta Plus Variant been found?
Delta plus has been found in ten countries including India, USA and UK.
In India, the Delta plus variant has been detected in around 40 samples from 7 states. At least 16 of these samples were found in Maharashtra, one of the states hardest hit by the pandemic. Since these samples were from April, we believe that the actual numbers must be much more now in June. Since the numbers detected to date are still very few, the implications of the new variant remains to be completely understood.
What may be effect of this new mutation K417N?
- The mutation K417N has been of interest as it is present in the Beta variant (B.1.351 lineage), which was reported to have immune evasion property.
- Some scientists worry that K417N could make it more transmissible but there is no evidence to confirm this yet. The variant has already been present in some states for the last two months, there has still not been any ‘rapid’ resurgence in number of cases. The slow increase in cases now visible in some states may also be attributed to the gradual unlocking and is not necessarily a sign of the much feared third wave.
- This K417N mutation reduces the effectiveness of the monoclonal antibody cocktail therapy in which artificial antibodies are used to treat a Covid patient, unlike the delta variant which does respond to the therapy.
What we still do not know entirely is will this variant escape vaccine immunity?
There may be some setback in the use of this monoclonal antibody cocktail due to the new variant if it becomes more prevalent. But resistance to this therapy is not an indicator of higher virulence or severity of illness. Scientists believe that at an individual patient level, infection with delta plus variant is unlikely to worsen the severity of the infection compared to the delta variant.
But for the population at large, it still needs to be determined if this mutation may result in decreased efficacy of the vaccine.
When it comes to the Delta variant, researchers have found both AstraZeneca (Covishield in India) and Pfizer vaccines effective in reducing the risk of SARS-CoV-2 infection and hospitalization. However, protection from infection appeared to be diminished when compared to patients with the Alpha variant, particularly after a single vaccine dose, although substantial protection from hospitalization remains. To assess whether the new variant shows any significant immune escape from the vaccine immunity, the blood plasma from several fully vaccinated individuals will have to be tested against this new variant.
The most important question is whether vaccines protect from severe or lethal Covid-19 vis-à-vis the Delta plus variant, particularly after a single dose. Depending on the answer to this question (as more data evolves) along with increased vaccine production, we may need to consider decreasing the duration between the Covishield doses to 4-8 weeks.
Although studies have shown that the antibodies wane over time, we do believe that those who recovered from a Delta variant illness during the second wave will have some protection from the Delta plus variant for atleast the next few months. This alongwith improving vaccine coverage might prevent a disastrous third wave, if at all it is to occur.
We also need to acknowledge the fact that many countries like Japan have averted all their waves even without vaccination. This is a reminder that irrespective of strains and vaccine efficacy, what continues to remain just as effective is strict masking, avoiding super-spreader events and well ventilated spaces. Strict policies to ensure this are just as crucial as ramping up the vaccination drive. Increasing genomic studies on existing covid samples will help us predict trends and preempt necessary strategies to stop a looming third wave.
(Dr. Trupti Gilada, Consultant Physician in Infectious Disease, Masina Hospital)
