Virus may be evolving to refavour infecting lung tissue. We assess what this could mean for the course of the pandemic
in the UK on 20 May, having first been detected in South Africa during January and February of this year.
However, with immunity from third vaccine doses waning in most population groups, and only the over-75s, and extremely vulnerable groups having been offered “spring booster” doses, this cannot be guaranteed. Neither is recent infection with the BA.1 or BA.2 Omicron variants necessarily protection against reinfection with BA.4 or BA.5.
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.These variants also appear to have a higher reproduction number than BA.2, while further experiments by Sato’s lab indicate that BA.4 and BA.5 may be resistant to immunity induced by earlier Omicron infections .