The BA.2 subtype of the Omicron coronavirus variant appears to have a substantial growth advantage over the currently predominant BA.1 type, Britain's UK Health Security Agency said on Friday.
UKHSA said that there was an increased growth rate of BA.2 compared with BA.1 in all regions of England where there were enough cases to compare them, and that "the apparent growth advantage is currently substantial".
"We now know that BA.2 has an increased growth rate which can be seen in all regions in England," said Dr Susan Hopkins, Chief Medical Advisor for the UKHSA.
The agency said there was no data on the severity of BA.2 compared to BA.1, but reiterated that a preliminary assessment did not find a difference in vaccine effectiveness against symptomatic disease between the two Omicron subtypes.
Frequently Asked Questions
A vaccine works by mimicking a natural infection. A vaccine not only induces immune response to protect people from any future COVID-19 infection, but also helps quickly build herd immunity to put an end to the pandemic. Herd immunity occurs when a sufficient percentage of a population becomes immune to a disease, making the spread of disease from person to person unlikely. The good news is that SARS-CoV-2 virus has been fairly stable, which increases the viability of a vaccine.
There are broadly four types of vaccine — one, a vaccine based on the whole virus (this could be either inactivated, or an attenuated [weakened] virus vaccine); two, a non-replicating viral vector vaccine that uses a benign virus as vector that carries the antigen of SARS-CoV; three, nucleic-acid vaccines that have genetic material like DNA and RNA of antigens like spike protein given to a person, helping human cells decode genetic material and produce the vaccine; and four, protein subunit vaccine wherein the recombinant proteins of SARS-COV-2 along with an adjuvant (booster) is given as a vaccine.
Vaccine development is a long, complex process. Unlike drugs that are given to people with a diseased, vaccines are given to healthy people and also vulnerable sections such as children, pregnant women and the elderly. So rigorous tests are compulsory. History says that the fastest time it took to develop a vaccine is five years, but it usually takes double or sometimes triple that time.
The rapid spread of BA.1 fuelled an Omicron wave which pushed cases to record highs in Britain in December, displacing the previously dominant Delta variant.
However, hospitalisations did not rise to the same extent, owing to population immunity through vaccination and previous infection, as well as Omicron's lower severity.
The UKHSA said that a separate analysis showed that between Nov 24 and Jan 19, the majority of intensive care admissions from COVID-19 had Delta infections, even as Omicron was growing to dominate the number of cases.
It also found that a rise of cases of Omicron in care homes had not been associated with an increase in hospital admissions.
"Our findings suggest the current wave of Omicron infections is unlikely to lead to a major surge in severe disease in care home populations with high levels of vaccine coverage and/or natural immunity," UKHSA said, noting that the findings were based on BA.1 due to limited numbers of BA.2 cases in the study.