New York: People infected with the earliest version of the Omicron variant of coronavirus at the start of the year could be reinfected with later versions of Omicron, as new findings suggest that even being vaccinated and boosted may not provide protection.
Vaccinated patients with Omicron BA.1 breakthrough infections developed antibodies that could neutralise that virus plus the original SARS-CoV-2 virus, but researchers from China reported on Friday in Nature that sublineages circulating now have mutations that evade those antibodies.
Omicron BA.2.12.1, which causes most infections in the United States now, and Omicron BA.5 and BA.4, which account for more than 21 per cent of new US cases, contain mutations not present in the BA.1 and BA.2 versions of Omicron.
The study from China found new Omicron variants have sublineages that evade the immunity built into early vaccines. Credit:Queensland Health
The BA.5 variation looks set to overtake the BA.2 strain as the dominant strain in NSW, the latest health department respiratory surveillance report, although BA.2 is still the most prevalent variant in other Australian states so far.
Those newer sublineages “notably evade the neutralising antibodies elicited by SARS-CoV-2 infection and vaccination,” the researchers found in test-tube experiments.
The monoclonal antibody drugs bebtelovimab from Eli Lilly and cilgavimab, a component of AstraZeneca’s Evusheld, can still effectively neutralise BA.2.12.1 and BA.4/BA.5, the experiments also showed.
But vaccine boosters based on the BA.1 virus, such as those in development by Pfizer/BioNTech and Moderna, “may not achieve broad-spectrum protection against new Omicron variants,” the researchers warned.
Previous research that has not yet undergone peer review has suggested that unvaccinated people infected with Omicron are unlikely to develop immune responses that will protect them against other variants of the coronavirus.
“My personal bias is that while there may be some advantage to having an Omicron-specific vaccine, I think it will be of marginal benefit over staying current with the existing vaccines and boosters,” said Dr Onyema Ogbuagu, a Yale infectious diseases researcher who was not involved in the new study.
“Despite immune evasion, the expectation can be that vaccines will still protect against serious disease,” Ogbuagu said. “If you’re due for a booster, get a booster. What we’ve learned clinically is that it’s most important to stay up-to-date with vaccines” to maintain high levels of COVID-19 antibodies circulating in the blood.
Adolfo Garcia-Sastre, a microbiology and infectious diseases researcher at the Icahn School of Medicine, suggested that vaccines that target multiple strains of the virus might give better protection. He also suggested nasal-spray vaccines would increase protection from infection and transmission by generating immunity in the lining of the nose, where the virus first enters.
Garcia-Sastre, who was not involved in the research, said by the time one variant-specific vaccine becomes available, a new variant may well have taken over.
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