Covid-19 Update | AY.1, AY.2 To AY.3.1 — What We Know So Far About Delta Plus Sub-Lineages

Delta or B.1.617.2, first identified in India in Oct 2020, is now a variant of concern globally. It further mutated & now has a total of 13 sub-lineages, from AY.1 to AY.12 — and the latest, AY.3.1.

Representative Image | AY.1, AY.2 To AY.3.1 — What We Know So Far About Delta Plus Sub-Lineages

New Delhi: Mumbai last week recorded the first death of a fully vaccinated person due to the Delta Plus variant of Covid-19. A 63-year-old woman, who had received both doses of the vaccine, died on July 27 but state government authorities came to know only on August 11 that she was infected with the Delta Plus variant.

The matter came to light in the genome sequencing report, news agency PTI quoted a Brihanmumbai Municipal Corporation (BMC) official has having said last week.

Delta Plus is considered highly infectious, and the government declared it a variant of concern (VOC) in India in June after 22 cases were detected across the country.

By August 17, Maharashtra alone had 76 cases of the Delta Plus variant.

According to experts, the Delta Plus strains behave similarly to the Delta variant.

A study conducted by the Indian Council of Medical Research (ICMR) in Chennai has now said the Delta variant can infect both vaccinated and unvaccinated people, though it reduces mortality among the former group.

 

What Is Delta Plus?

Delta, first identified in India in October 2020, is now a VOC globally. The variant, currently predominant strain circulating across the world, was a primary driver for the devastating Covid second wave in India.

The United States' Centers for Disease Control and Prevention (CDC) has said the Delta variant causes more infections and is “more than 2x as contagious” as the early forms of SARS-CoV-2.

Those infected with this variant have been reported to have 1,000 times higher viral loads. 

Delta has spread so much already that it now has several sub-variants, which are referred to as ‘Delta Plus’. 

The Delta or B.1.617.2 first mutated to B.1.617.2.1 — or AY.1. It now has a total of 13 sub-lineages, from AY.1 to AY.12 — and the latest, AY.3.1.

According to global experts, Delta Plus variants have an additional mutation in the spike protein that is also found in Beta and Gamma variants.

“Delta Plus has been reported first in India, but the type of mutation was reported in variants such as Beta that emerged earlier,” according to Dr Inci Yildirim, vaccinologist and Yale Medicine pediatric infectious diseases specialist. 

She says K417N, the additional mutation, “affects the spike protein that the virus needs to infect cells”, and that is the main target for the vaccines.

While declaring Delta Plus as a VOC in India, the health ministry had said it spreads more easily, latches on to your lung cells more effectively, and could be resistant to monoclonal antibodies and other therapies used to treat the virus infection.

Delta Plus And Vaccination  

Acknowledging that the “highly transmissible” Delta variant is becoming a dominant strain across the globe, the World Health Organization has said the surge increases the “urgency for vaccinating large numbers of vulnerable people”.

Most of the Covid-19 vaccines approved for use globally claim to be effective against Delta, and experts stress that the risk from all Delta variants is significantly lower after vaccination.

A Public Health England analysis (preprint) in May this year said studies had found the Pfizer-BioNTech and Oxford-AstraZeneca vaccines 88 per cent and 60 per cent effective, respectively, against symptomatic disease and 96 per cent and 93 per cent effective, respectively, against hospitalisation. The participants tracked for the studies who were vaccinated with both doses.

In June, Moderna also reported that studies (not peer-reviewed yet) found its vaccine to be effective against Delta, noting only a “modest reduction in neutralizing titers” when compared to its effectiveness against the original variant. 

There are, however, additional concerns about Delta Plus. A recent study (pre-print) by researchers in Boston said transmission of the Delta Variant AY.3 could occur  among fully vaccinated people even in a controlled environment of an inpatient medical-surgical ward.

“It remains to be determined whether the Delta variant AY.3 lineage is more transmissible than the Delta Variant B.1.617.2,” the paper noted. “Our findings do raise concern that without stricter risk mitigation, nosocomial (originating in a hospital) transmission of the Delta variant and Delta sub-lineages will occur more frequently than with prior, less transmissible variants, even in vaccinated persons.” 

In an interview with The Times of India, Vinod Scaria, who is working with the Maharashtra public health department on the genome surveillance project mentioned above, said the urgent priority should be to vaccinate the entire population.

He stressed that none of the emergent sub-lineages “can so far fully escape the immunity due to previous infections or vaccines”. 

The Joe Biden administration has meanwhile recommended that people in the US who had received the Pfizer-BioNTech or Moderna (mRNA) vaccines should get a booster shot eight months after the second dose. The advisory was based on the spread of Delta, and CDC studies that suggested the protection given by the vaccines were on the wane. 

The boosters would be available as early as September 20, if the Food and Drug Administration (FDA) gives its nod to the plan, The New York Times reported on Wednesday.