A new study by Harvard Medical school claims that Omicron subvariants BA.4 and BA.5 appear to escape antibody responses among both those who had an infection and those who have been fully vaccinated and boosted.
“We observed 3-fold reductions of neutralizing antibody titers induced by vaccination and infection against BA4 and BA5 compared with BA1 and BA2, which are already substantially lower than the original Covid-19 variants,” Dr Dan Barouch, an author of the paper and director of the Center for Virology and Vaccine Research in Boston told CNN.
However, Dr Barouch added that Covid-19 vaccines can still provide substantial protection against severe infection and informed CNN that vaccine makers are working to produce a much stronger booster dose that can challenge stronger variants like Omicron.
Since the outbreak of Covid-19 in China in late 2019, as many as five variants — Alpha, Beta, Gamma, Delta and Omicron — have been identified with Omicron being the most transmissible. It still persists and continues to prevail in many countries, including India, despite millions being inoculated. However, Omicron is considered less infectious as the rate of severe infection and fatality is relatively low.
Omicron’s subvariants BA.4 and BA.5 are the fastest spreading variants reported to date, and they are expected to dominate transmission in the United States, United Kingdom and the rest of Europe within the next few weeks, according to the European Centre for Disease Prevention and Control.
The ability of vaccine or previous infection to neutralise the BA.4 and BA.5 subvariants of Omicron, is several times lower compared with the original coronavirus, as per the study published in the New England Journal of Medicine.
“Our data suggest that these new Omicron subvariants will likely be able to lead to surges of infections in populations with high levels of vaccine immunity as well as natural BA1 and BA2 immunity,” Dr Barouch wrote in the research.
In the study, among 27 research participants who had been vaccinated and boosted with the Pfizer/BioNTech coronavirus vaccine, the researchers found that two weeks after the booster dose, levels of neutralising antibodies against Omicron subvariants were much lower than the response against the original coronavirus.
The neutralising antibody levels were lower by a factor of 6.4 against BA.1; by a factor of 7 against BA.2; by a factor of 14.1 against BA.2.12.1 and by a factor of 21 against BA.4 or BA.5, the researchers described.
Also, among 27 participants who had previously been infected with the BA.1 or BA.2 subvariants a median of 29 days earlier, the researchers found similar results.
“Our data suggest that Covid-19 still has the capacity to mutate further, resulting in increased transmissibility and increased antibody escape,” the author said.
The US Centers for Disease Control and Prevention estimates that 94.7 per cent of the US population aged 16 and older have antibodies against the coronavirus through vaccination, infection, or both.
However, BA.4 and BA.5 led to an estimated 35 per cent of new Covid-19 infections in the United States last week, up from 29 per cent the week before, according to data from US Centers for Disease Control and Prevention.