BA.4, BA.5 subvariants of Omicron evade immunity, need to keep a watch on hospitalisation, says researcher

Published on May 29, 2022 10:51 PM IST

The subvariants of Omicron were confirmed for the first time in the state by Pune-based Byramjee Jeejeebhoy Government Medical College

The confirmation of BA.4 and BA.5 subvariants of the Omicron strain of Sars-CoV-2 virus causing Covid-19 has led to both curiosity and caution among the general public and health experts. (HT FILE PHOTO)
The confirmation of BA.4 and BA.5 subvariants of the Omicron strain of Sars-CoV-2 virus causing Covid-19 has led to both curiosity and caution among the general public and health experts. (HT FILE PHOTO)
BySteffy Thevar

PUNE The confirmation of BA.4 and BA.5 subvariants of the Omicron strain of Sars-CoV-2 virus causing Covid-19 has led to both curiosity and caution among the general public and health experts. To get more clarity on the same, Hindustan Times spoke with the researcher who first confirmed the variants in samples from Pune city patients.

Dr Rajesh Karyakarte, head of the microbiology department at Byramjee Jeejeebhoy Government Medical College, confirmed that the variants could evade immunity as to all the patients, except a child, had got both doses of the vaccine but were fully stable and required to be home isolated. However, he also advised that we need to keep a close watch on hospitalisations.

The subvariants of Omicron were confirmed for the first time in the state by Pune-based Byramjee Jeejeebhoy Government Medical College, which was also instrumental in finding mutations in the Sars-CoV-2 virus of Kappa and Delta variants.

Dr Karyakarte said, “It is confirmed that the variants can evade immunity as to all the seven patients, excluding the kid, whose samples we sequenced had taken two shots of the vaccine and one had even taken a booster dose. Although all these patients were isolated at home as their symptoms were mild, we need to keep a keen watch on hospitalisations.”

According to Dr Karyakarte, international studies have shown that the new variants of BA.4 and BA.5 have the characteristics of both BA.2 which is faster in transmission and also Delta defining mutations which are to be able to infect the lungs, which were not possible by BA.2.

Dr Karyakarte added that since both, Delta and BA.2, are already prevalent in the community and due to high vaccination, which has given herd immunity to the majority of the public so the risk of hospitalisations could be less, however, this is a hypothesis.

The study conducted by international researchers and scholars from Japan and was posted in BioRxiv on May 26, 2022, states that the cell culture experiments showed that BA.2.12.1 and BA.4/5 replicate more efficiently in human alveolar epithelial cells than BA.2, and particularly, BA.4/5 is more fusogenic, the ability to penetrate cells, than BA.2. Furthermore, infection experiments using hamsters indicated that BA.4/5 is more pathogenic, causing more disease than BA.2.

“Altogether, the multi-scale investigations suggest that the risk of L452R/M/Q-bearing BA.2-related Omicron variants, particularly BA.4 and 97 BA.5, to global health is potentially greater than that of original BA.2,” the study stated.

The study further states that BA.4/5 is resistant to the immunity induced by BA.1 and BA.2 infections and that BA.2.12.1 and BA.4/5 more efficiently spread in human lung cells than BA.2. BA.4/5 is more pathogenic than BA.2 in hamsters.

Since the reporting of the new variant, the public health department has advised caution to restart wearing masks and has advised people to get fully vaccinated and go for booster doses. Of the seven patients whose samples confirmed the new variants, all except a nine-year-old were vaccinated and had developed only mild symptoms.

Dr Karyakarte added that more information and sequencing of samples are required to understand the impact of the variant on those with comorbidity and those who are elderly.

According to Dr Pradeep Awate, state surveillance officer, the health department’s immunisation wing has started focusing on increasing vaccination and urging people to get both the doses as well as the booster dose.

“As of now, we do not know the co-morbidity status of these seven patients, however, going by their age, of the seven, four are above 50 years, and one is above 60 years, so they are most likely to have diabetes or hypertension. Also, based on the observations from other countries like South Africa, where this particular strain has been prevalent since January, it has been found that the severity is not any different from the original Omicron strain but just that it is faster in transmission. Therefore, the number of cases may go up but not to the extent of becoming a wave-like before, and it is highly unlikely that the rate of hospitalisations may go up,” Awate said.

In the light of rising cases in parts of the state, chief minister Uddhav Thackeray has asked that those most vulnerable should start wearing masks in public places as even a mild infection could take a turn for worse.

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