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Prior infection of Omicron protects from BA.4 and BA.5 sub-variants, says study

The latest BA.4 and BA.5 sub-variants are currently quite prevalent in the South Indian states, say experts.

Sumit Jha

Published Jul 23, 2022 | 1:06 PM ⚊ Updated Jul 28, 2022 | 4:05 PM

July’s month data from GISAID and Karnataka reveals BA.5 and its sublineages BA.2 and BA.2.75 make up a large proportion of the cases.

July’s month data from GISAID and Karnataka reveals BA.5 and its sublineages BA.2 and BA.2.75 make up a large proportion of the cases. (File Photo)

Your chances of getting infected with Omicron BA.4 and BA.5 sub-variants of Covid-19 — currently prevalent in south Indian states — are less if you were already infected with other variants of Omicron.

In a study published in medRxiv, researchers found that those infected by older variants such as Alpha, Beta or Delta got some protection against the BA.4 and BA.5 sub-variants.

“Protection of a previous infection against BA.4/BA.5 reinfection was modest when the previous infection involved a pre-Omicron variant, but strong when the previous infection involved the Omicron BA.1 or BA.2 subvariant,” the study says.

Variants in southern states

Omicron sub-variants BA.4 and BA.5 were found among people during the latest rounds of genome sequencing in Andhra Pradesh, the state’s Vaidya Vidhana Parishad Commissioner Dr Vinod Kumar said on 21 July.

The state has been carrying out random genome sequencing tests on swab samples. Tests are done on 32 swab samples at a stretch per cycle and the results are out in 36 hours.

Health authorities say that on an average, subjecting 10 to 12 per cent of the swab samples to genome sequencing tests showed the prevalence of Omicron sub-variants BA.4 and BA.5.

“This means that their presence is more than the other sub-variants like BA2.75,” said Dr Kumar.

Omicron BA.5 variant has recently been causing havoc in several countries, including the US, where scientists and epidemiologists have even taken to Twitter to warn of a surge in hospitalisations and ICU admissions due to Covid-19.

“It’s not #BA5 alone which is resulting in the #reinfection wave. New sublineages will evolve and will infect those who are at the risk will get infected,” tweeted Dr Giridhara R Babu, epidemiologist and a member of the Technical Advisory Committee from Karnataka, on 14 July.

Also, BA.2.75 is circulating at a higher rate.

Sequence count: 511

The growth advantage of BA.2.75 over other circulating lineages in India is clear!

— Raj Rajnarayanan (@RajlabN) July 22, 2022

Risk of reinfection

The study found that infection with a pre-Omicron variant prevented reinfection with BA.4 or BA.5 with an effectiveness of 28.3 percent, and prevented symptomatic reinfection with either sub-variant with an effectiveness of 15.1 percent.

Prior infection with Omicron granted stronger protection: It was 79.7 percent effective at preventing BA.4 and BA.5 reinfection and 76.1 percent effective at preventing symptomatic reinfection.

“In generally healthy population, the risk of serious disease with the variants circulating now is very, very low, and is even lower after prior infection,” Dr Gagandeep Kang, Microbiologist and Professor, CMC Vellore, told South First.

However, another expert advises citizens to get vaccinated and follow Covid-19 appropriate behaviour.

“All these variants are now better than the previous one on their immune properties. Every variant is very similar; BA.5 looks like it is better in immune escape… but the trend will be that people would not have so many symptoms, they will get infected, but only mild symptoms will appear. So, I will suggest that citizens get vaccinated ,” Dr Rakesh Mishra, former director, CCMB, Hyderabad told South First.

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