London: The increasing cases of Covid, in the UK, US and some European countries, as well as India, mainly driven by BA.2, BA.4 and BA.5 sub-variants of Omicron, suggest it may have evolved to protect the lungs target, according to a study.
Separately, two studies also showed their potential to escape vaccine-induced immunity and that of previous infections.
The highly contagious Omicron variant of Covid was once known to affect the upper respiratory tract more than the lungs, unlike Delta, and cause cold-like symptoms. This may explain why infections are milder in most people.
But now a preliminary study from the University of Tokyo showed that BA.4, BA.5 and BA.2.12.1 may have evolved to cause infection of lung cells. This allows the sub-variants to resemble earlier variants, such as Alpha or Delta, the Independent reported.
“Overall, our studies suggest that the global health risk of (these) Omicron variants, particularly BA.4 and BA.5, may be greater than that of the original BA.2,” said Kei Sato of the university.
Sato’s experiments indicate that BA.4, BA.5 and BA.2.12.1 replicate more efficiently in human lung cells than BA.2, while further experiments in hamsters suggest that BA.4 and BA.5 may cause more severe disease, the report said.
“Looks like these things are switching back to the more dangerous form of infection, so lower in the lungs,” said Dr. Stephen Griffin, a virologist at the University of Leeds, says.
This could also be the case in India, where patients show more severe symptoms than during the earlier Omicron wave, Dr. Neha Gupta, Consultant Infectious Disease, Fortis Memorial Research Institute, Gurugram, to IANS.
India reported 13,313 new cases of Covid-19 and 38 deaths in the past 24 hours on Thursday, according to data from the health ministry.
“During this wave, we have seen patients with moderate to severe Covid-19, which is slightly more severe compared to the Omicron variant,” Gupta said.
Furthermore, a study led by researchers from the Beth Israel Deaconess Medical Center, of Harvard Medical School, showed that BA.4 and BA.5 seem to escape antibody responses in both people who had a previous Covid-19 infection and those who have been fully vaccinated and boosted, CNN reported.
The research published in the New England Journal of Medicine revealed a 3-fold reduction in the levels of neutralizing antibodies triggering previous infection or vaccinations against the BA.4 and BA.5 subvariants compared to the parent coronavirus.
However, the team added that “vaccine immunity will still provide substantial protection against serious diseases involving BA4 and BA5”.
A separate study by scientists at Columbia University showed that the BA.4 and BA.5 viruses were more likely to escape antibodies from the blood of fully vaccinated and boosted adults compared to other Omicron subvariants, increasing the risk on vaccine breakthrough Covid -19 infections increased, the report said.